Patent Publication Number: US-8979758-B2

Title: Sensing module for orthopedic load sensing insert device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority benefit of U.S. provisional patent applications No. 61/221,761, 61/221,767, 61/221,779, 61/221,788, 61/221,793, 61/221,801, 61/221,808, 61/221,817, 61/221,867, 61/221,874, 61/221,879, 61/221,881, 61/221,886, 61/221,889, 61/221,894, 61/221,901, 61/221,909, 61/221,916, 61/221,923, and 61/221,929 all filed 30 Jun. 2009; the disclosures of which are hereby incorporated herein by reference in their entirety. 
     FIELD 
     The present invention pertains generally to a joint prosthesis, and particularly to methods and devices for assessing and determining proper alignment and placement of an implant component or components during joint reconstructive surgery and long-term implantation. 
     BACKGROUND 
     The skeletal system of a mammal is subject to variations among species. Further changes can occur due to environmental factors, degradation through use, and aging. An orthopedic joint of the skeletal system typically comprises two or more bones that move in relation to one another. Movement is enabled by muscle tissue and tendons attached to the skeletal system of the joint. Ligaments hold and stabilize the one or more joint bones positionally. Cartilage is a wear surface that prevents bone-to-bone contact, distributes load, and lowers friction. 
     There has been substantial growth in the repair of the human skeletal system. In general, orthopedic joints have evolved using information from simulations, mechanical prototypes, and patient data that is collected and used to initiate improved designs. Similarly, the tools being used for orthopedic surgery have been refined over the years but have not changed substantially. Thus, the basic procedure for replacement of an orthopedic joint has been standardized to meet the general needs of a wide distribution of the population. Although the tools, procedure, and artificial joint meet a general need, each replacement procedure is subject to significant variation from patient to patient. The correction of these individual variations relies on the skill of the surgeon to adapt and fit the replacement joint using the available tools to the specific circumstance. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various features of the system are set forth with particularity in the appended claims. The embodiments herein, can be understood by reference to the following description, taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is an illustration of an application of sensing insert device in accordance with an exemplary embodiment; 
         FIG. 2  is an illustration of a sensing insert device placed in a joint of the muscular-skeletal system for measuring a parameter in accordance with an exemplary embodiment; 
         FIG. 3  is a perspective view of a medical sensing platform comprising an encapsulating enclosure in accordance with one embodiment; 
         FIG. 4  is a perspective view of a medical sensing device suitable for use as a bi-compartmental implant and comprising an encapsulating enclosure in accordance with one embodiment; 
         FIG. 5  is an exemplary block diagram of the components of the sensing module in accordance with an exemplary embodiment; 
         FIG. 6  is a diagram of an exemplary communications system for short-range telemetry according to one embodiment; 
         FIG. 7  is an illustration of a block model diagram of the sensing module in accordance with an exemplary embodiment; 
         FIG. 8  is an exemplary assemblage that illustrates propagation of ultrasound waves within the waveguide in the bi-directional mode of operation of this assemblage in accordance with one embodiment; 
         FIG. 9  is an exemplary cross-sectional view of an ultrasound waveguide to illustrate changes in the propagation of ultrasound waves with changes in the length of the waveguide in accordance with one embodiment; 
         FIG. 10  is an exemplary block diagram of a propagation tuned oscillator (PTO) to maintain positive closed-loop feedback in accordance with an exemplary embodiment; 
         FIG. 11  is a cross-sectional view of a layout architecture of the sensing module in accordance with an exemplary embodiment; 
         FIG. 12  is a simplified cross-sectional view of an embodiment of the load sensing platform in accordance with an exemplary embodiment; 
         FIG. 13  is an illustration of an exemplary data packet containing sensor data; 
         FIG. 14  is an exemplary block diagram schematic of a compact low-power energy source integrated into an exemplary electronic assembly of the sensing module in accordance with one embodiment; 
         FIG. 15  is a partial cross-section schematic side view of a sensing platform including multiple constructed levels comprising electronic substrates with electronic components mounted thereon in accordance with an exemplary embodiment; 
         FIG. 16  is a partial cross-section schematic side view of the sensing platform including multiple constructed levels comprising electronic substrates with electronic components mounted thereon in accordance with an exemplary embodiment; 
         FIG. 17  is a partial cross-section schematic side view of a sensing module including multiple constructed levels comprising electronic substrates with electronic components mounted thereon in accordance with an exemplary embodiment; 
         FIG. 18  is a cross-sectional view of the sensing module having a small form factor in accordance with an exemplary embodiment; 
         FIG. 19  is a perspective view of the interconnect stack of the sensing module in accordance with an exemplary embodiment; 
         FIG. 20  is a partial cross-section schematic side view of a sensing platform including multiple constructed levels comprising electronic substrates with electronic components mounted thereon in accordance with an exemplary embodiment; 
         FIG. 21  is a partial cross-section schematic side view of the sensing platform including multiple constructed levels comprising electronic substrates with electronic components mounted thereon in accordance with an exemplary embodiment; 
         FIG. 22  is a partial cross-section schematic side view of a sensing module including multiple constructed levels comprising electronic substrates with electronic components mounted thereon in accordance with an exemplary embodiment; 
         FIG. 23  is a perspective view of an exemplary loop antenna in accordance with one embodiment; 
         FIG. 24  is a perspective view of an integrated loop antenna according to another embodiment; 
         FIG. 25  Illustrates by way of example a plot of normalized radiated field strength versus frequency performance of an example loop antenna integrated into a flexible substrate of the electronic circuit board; 
         FIG. 26  Illustrates a radiation pattern of the loop antenna integrated into a flexible substrate of an electronic circuit in accordance with an exemplary embodiment; 
         FIG. 27  illustrates a low power consumption integrated transducer driver circuit in accordance with an exemplary embodiment; 
         FIG. 28  illustrates a block diagram of an edge-detect receiver circuit in accordance with an exemplary embodiment; 
         FIG. 29  is a block diagram of a zero-crossing receiver in accordance with one embodiment; 
         FIG. 30  is a sensor interface diagram incorporating the zero-crossing receiver in a continuous wave multiplexing arrangement for maintaining positive closed-loop feedback in accordance with one embodiment; 
         FIG. 31  is an exemplary block diagram of a propagation tuned oscillator (PTO) incorporating the zero-crossing receiver for operation in continuous wave mode; 
         FIG. 32  is a sensor interface diagram incorporating the integrated zero-crossing receiver in a pulse multiplexing arrangement for maintaining positive closed-loop feedback in accordance with one embodiment; 
         FIG. 33  is an exemplary block diagram of a propagation tuned oscillator (PTO) incorporating the zero-crossing receiver for operation in pulse mode in accordance with one embodiment; 
         FIG. 34  is a sensor interface diagram incorporating the edge-detect receiver circuit in a pulse-echo multiplexing arrangement for maintaining positive closed-loop feedback in accordance with one embodiment; 
         FIG. 35  is an exemplary block diagram of a propagation tuned oscillator (PTO) incorporating the edge-detect receiver circuit for operation in pulse echo mode in accordance with one embodiment; 
         FIG. 36  is a final insert in accordance with an exemplary embodiment; 
         FIG. 37  is a perspective view of sensing modules in final insert in accordance with an exemplary embodiment; and 
         FIG. 38  is an illustration of the final insert installed in a knee in accordance with an exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the invention are broadly directed to measurement of physical parameters. Many physical parameters of interest within physical systems or bodies can be measured by evaluating changes in the characteristics of energy waves or pulses. As one example, changes in the transit time or shape of an energy wave or pulse propagating through a changing medium can be measured to determine the forces acting on the medium and causing the changes. The propagation velocity of the energy waves or pulses in the medium is affected by physical changes in of the medium. The physical parameter or parameters of interest can include, but are not limited to, measurement of load, force, pressure, displacement, density, viscosity, localized temperature. These parameters can be evaluated by measuring changes in the propagation time of energy pulses or waves relative to orientation, alignment, direction, or position as well as movement, rotation, or acceleration along an axis or combination of axes by wireless sensing modules or devices positioned on or within a body, instrument, appliance, vehicle, equipment, or other physical system. 
     In all of the examples illustrated and discussed herein, any specific materials, temperatures, times, energies etc . . . for process steps or specific structure implementations should be interpreted to be illustrative only and non-limiting. Processes, techniques, apparatus, and materials as known by one of ordinary skill in the art may not be discussed in detail but are intended to be part of an enabling description where appropriate. 
     Note that similar reference numerals and letters refer to similar items in the following figures. In some cases, numbers from prior illustrations will not be placed on subsequent figures for purposes of clarity. In general, it should be assumed that structures not identified in a figure are the same as previous prior figures. 
     In the present invention these parameters are measured with an integrated wireless sensing module or device comprising an i) encapsulating structure that supports sensors and contacting surfaces and ii) an electronic assemblage that integrates a power supply, sensing elements, ultrasound resonator or resonators or transducer or transducers and ultrasound waveguide or waveguides, biasing spring or springs or other form of elastic members, an accelerometer, antennas and electronic circuitry that processes measurement data as well as controls all operations of energy conversion, propagation, and detection and wireless communications. The wireless sensing module or device can be positioned on or within, or engaged with, or attached or affixed to or within, a wide range of physical systems including, but not limited to instruments, appliances, vehicles, equipments, or other physical systems as well as animal and human bodies, for sensing and communicating parameters of interest in real time. 
       FIG. 1  is an illustration of an application of sensing insert device  100  in accordance with an exemplary embodiment. The medical device incorporates a loop antenna  107 . In this example, the medical device can intra-operatively assess a load on the prosthetic knee components (implant) and collect load data for real-time viewing of the load over various applied loads and angles of flexion. By way of the loop antenna  107 , a compact low-power energy source  117 , and associated transceiver electronics, the sensing insert device  100  can transmit measured load data to a receiver for permitting visualization of the level and distribution of load at various points on the prosthetic components. This can aid the surgeon in making any adjustments needed to achieve optimal joint balancing. The insert device  100  further includes a compact low-power energy source  117 . 
     In general, device  100  has at least one contacting surface that couples to the muscular-skeletal system. As shown, a first and a second contacting surface respectively couple to a femoral prosthetic component  104  and a tibial prosthetic component  106 . Device  100  is designed to be used in the normal flow of an orthopedic surgical procedure without special procedures, equipment, or components. Typically, one or more natural components of the muscular-skeletal system are replaced when joint functionality substantially reduces a patient quality of life. A joint replacement is a common procedure in later life because it is prone to wear over time, can be damaged during physical activity, or by accident. 
     A joint of the muscular-skeletal system provides movement of bones in relation to one another that can comprise angular and rotational motion. The joint can be subjected to loading and torque throughout the range of motion. The joint typically comprises two bones that move in relation to one another with a low friction flexible connective tissue such as cartilage between the bones. The joint also generates a natural lubricant that works in conjunction with the cartilage to aid in ease of movement. Sensing insert device  100  mimics the natural structure between the bones of the joint. Insert device  100  has a contacting surface on which a bone or a prosthetic component can movably couple. A knee joint is disclosed for illustrative purposes but sensing insert device  100  is applicable to other joints of the muscular-skeletal system. For example, the hip, spine, and shoulder have similar structures comprising two or more bones that move in relation to one another. In general, insert device  100  can be used between two or more bones allowing movement of the bones during measurement or maintaining the bones in a fixed position. 
     The load sensor insert device  100  and the receiver station  110  forms a communication system for conveying data via secure wireless transmission within a broadcasting range over short distances on the order of a few meters to protect against any form of unauthorized or accidental query. In one embodiment, the transmission range is five meters or less which is approximately a dimension of an operating room. In practice, it can be a shorter distance 1-2 meters to transmit to a display outside the sterile field. The transmit distance will be even shorter when device  100  is used in a prosthetic implanted component. Transmission occurs through the skin of the patient and is likely limited to less than 0.5 meters. A combination of cyclic redundancy checks and a high repetition rate of transmission during data capture permits discarding of corrupted data without materially affecting display of data 
     In the illustration, a surgical procedure is performed to place a femoral prosthetic component  104  onto a prepared distal end of the femur  102 . Similarly, a tibial prosthetic component  106  is placed to a prepared proximal end of the tibia  108 . The tibial prosthetic component  106  can be a tray or plate affixed to a planarized proximal end of the tibia  108 . The sensing insert device  100  is a third prosthetic component that is placed between the plate of the tibial prosthetic component  106  and the femoral prosthetic component  104 . The three prosthetic components enable the prostheses to emulate the functioning of a natural knee joint. In one embodiment, sensing insert device  100  is used during surgery and replaced with a final insert after quantitative measurements are taken to ensure optimal fit, balance, and loading of the prosthesis. 
     In one embodiment, sensing insert device  100  is a mechanical replica of a final insert. In other words, sensing insert device  100  has substantially equal dimensions to the final insert. The substantially equal dimensions ensure that the final insert when placed in the reconstructed joint will have similar loading and balance as that measured by sensing insert device  100  during the trial phase of the surgery. Moreover, passive trial inserts are commonly used during surgery to determine the appropriate final insert. Thus, the procedure remains the same. It can measure loads at various points (or locations) on the femoral prosthetic component  104  and transmit the measured data to a receiving station  110  by way of an integrated loop antenna  107 . The receiving station  110  can include data processing, storage, or display, or combination thereof and provide real time graphical representation of the level and distribution of the load. 
     As one example, the sensing insert device  100  can measure forces (Fx, Fy, and Fz) with corresponding locations and torques (e.g. Tx, Ty, and Tz) on the femoral prosthetic component  104  and the tibial prosthetic component  106 . It can then transmit this data to the receiving station  110  to provide real-time visualization for assisting the surgeon in identifying any adjustments needed to achieve optimal joint balancing. 
     In a further example, an external wireless energy source  125  can be placed in proximity to the medical sensing device  100  to initiate a wireless power recharging operation. As an example, the external wireless energy source  125  generates energy transmissions that are wirelessly directed to the medical sensing device  100  and received as energy waves via resonant inductive coupling. The external wireless energy source  125  can modulate a power signal generating the energy transmissions to convey downlink data that is then demodulated from the energy waves at the medical sensing device  100 . As described above, the sensing insert device  100  is a sensing insert device  100  suitable for use in knee joint replacement surgery. The external wireless energy source  125  can be used to power the sensing insert device  100  during the surgical procedure or thereafter when the surgery is complete and the sensing insert device  100  is implanted for long-term use. The method can also be used to provide power and communication where the sensing insert device  100  is in a final insert that is part of the final prosthesis implanted in the patient. 
     In one system embodiment, the sensing insert device  100  transmits measured parameter data to a receiver  110  via one-way data communication over the up-link channel for permitting visualization of the level and distribution of the parameter at various points on the prosthetic components. This, combined with cyclic redundancy check error checking, provides high security and protection against any form of unauthorized or accidental interference with a minimum of added circuitry and components. This can aid the surgeon in making any adjustments needed to optimize the installation. In addition to transmitting one-way data communications over the up-link channel to the receiver station  110 , the sensing insert device  100  can receive downlink data from the external wireless energy source  125  during the wireless power recharging operation. The downlink data can include component information, such as a serial number, or control information, for controlling operation of the sensing insert device  100 . This data can then be uploaded to the receiving system  110  upon request via the one-way up-link channel, in effect providing two-way data communications over separate channels. 
     Separating uplink and downlink telemetry eliminates the need for transmit-receive circuitry within the sensing insert device  100 . Two unidirectional telemetry channels operating on different frequencies or with different forms of energy enables simultaneous up and downlink telemetry. Modulating energy emissions from the external wireless energy source  125  as a carrier for instructions achieves these benefits with a minimum of additional circuitry and components by leveraging existing circuitry and antenna, induction loop, or piezoelectric components on the load sensor insert device  100 . The frequencies of operation of the up and downlink telemetry channels can also be selected and optimized to interface with other devices, instruments, or equipment as needed. Separating uplink and downlink telemetry also enables addition of downlink telemetry without altering or upgrading existing chip-set telemetry for the one-way transmit. That is, existing chip-set telemetry can be used for encoding and packaging data and error checking without modification, yet remain communicatively coupled to the separate wireless power down-link telemetry operation for download operations herein contemplated. 
     As shown, the wireless energy source  125  can include a power supply  126 , a modulation circuit  127 , and a data input  128 . The power supply  126  can be a battery, a charging device, a capacitor, a power connection, or other energy source for generating wireless power signals to power the sensing insert device  100 . The external wireless energy source can transmit energy in the form of, but not limited to, electromagnetic induction, or other electromagnetic or ultrasound emissions. In at least one exemplary embodiment, the wireless energy source  125  includes a coil to electromagnetically couple with an induction coil in sensing device  100  when placed in close proximity. The data input  128  can be a user interface component (e.g., keyboard, keypad, or touchscreen) that receives input information (e.g., serial number, control codes) to be downloaded to the load sensor insert device  100 . The data input  128  can also be an interface or port to receive the input information from another data source, such as from a computer via a wired or wireless connection (e.g., USB, IEEE802.16, etc.). The modulation circuitry  127  can modulate the input information onto the power signals generated by the power supply  126 . 
       FIG. 2  is an illustration of a sensing insert device  100  placed in a joint of the muscular-skeletal system for measuring a parameter in accordance with an exemplary embodiment. In particular, sensing insert device  100  is placed in contact between a femur  102  and a tibia  108  for measuring a parameter. In the example, a force, pressure, or load is being measured. The device  100  in this example can intra-operatively assess a load on prosthetic components during the surgical procedure. As mentioned previously, sensing insert device  100  collects data for real-time viewing of the load forces over various applied loads and angles of flexion. It can measure the level and distribution of load at various points on the prosthetic component and transmit the measured load data by way data communication to a receiver station  110  for permitting visualization. This can aid the surgeon in making any adjustments needed to achieve optimal joint balancing. 
     A proximal end of tibia  108  is prepared to receive tibial prosthetic component  106 . Tibial prosthetic component  106  is a support structure that is fastened to the proximal end of the tibia and is usually made of a metal or metal alloy. The tibial prosthetic component  106  also retains the insert in a fixed position with respect to tibia  108 . Similarly, a distal end of femur  102  is prepared to receive femoral prosthetic component  104 . The femoral prosthetic component  104  is generally shaped to have an outer condylar articulating surface. The preparation of femur  102  and tibia  108  is aligned to the mechanical axis of the leg. The sensing insert device  100  provides a concave or flat surface against which the outer condylar articulating surface of the femoral prosthetic component  104  rides relative to the tibia prosthetic component  106 . In particular, the top surface of the sensing module  200  faces the condylar articulating surface of the femoral prosthetic component  104 , and the bottom surface of the insert dock  202  faces the top surface of the tibial prosthetic component  106 . 
     A final insert is subsequently fitted between femoral prosthetic component  104  and tibial prosthetic component  106  that has a bearing surface that couples to femoral component  104  allowing the leg a natural range of motion. The final insert is has a wear surface that is typically made of a low friction polymer material. Ideally, the prosthesis has an appropriate loading, alignment, and balance that mimics the natural leg and maximizes the life of the artificial components. It should be noted that sensing module  200  can be placed a final insert and operated similarly as disclosed herein. The sensing module  200  can be used to periodically monitor status of the permanent joint. 
     The sensing insert device  100  is used to measure, adjust, and test the reconstructed joint prior to installing the final insert. As mentioned previously, the sensing insert device  100  is inserted between the femur  102  and tibia  108 . The condyle surface of femoral component  104  contacts a major surface of device  100 . The major surface of device  100  approximates a surface of a final insert. Tibial prosthetic component  106  can include a cavity or tray on the major surface that receives and retains an insert dock  202  and a sensing module  200  during a measurement process. Each insert dock  202  has an opening to receive the sensing module  200 . In one embodiment, the insert dock  202  can be of different sizes and shapes but each accepts the same sensing module  200 . It should be noted that sensing insert device  100  is coupled to and provides measurement data in conjunction with other implanted prosthetic components. In other words, the prosthetic components are the permanent installed components of the patient. 
     Insert dock  202  is provided in different sizes and shapes. Insert dock  202  can comprise many different sizes and shapes to interface appropriately with different manufacturer prosthetic components. Prosthetic components are made in different sizes to accommodate anatomical differences over a wide population range. Similarly, insert dock  202  is designed for different prosthetic sizes manufactured by the same company. In at least one embodiment, multiple docks of different dimensions are provided for a surgery. In general, the docks are selected having a major surface that fit a corresponding major surface of the tibial prosthetic component  106 . More than one dock can be provided each having a different height or thickness. The thickness of the final insert is determined by the surgical cuts to the muscular-skeletal system and measurements provided by sensing module  200 . The surgeon selects dock  202  based on the gap between the femur and tibial cuts. The surgeon inserts the sensing module  200  in an opening of the selected dock. The selected dock  202  and sensing module  200  are then inserted in the knee joint to interact with the final femoral and tibial prosthetic components. The surgeon may try two or more insert docks  202  of different thicknesses (or height) before making a final decision. Each trial by the surgeon can include modifications to the joint and tissue. In one embodiment, sensing insert device  100  selected by the surgeon has substantial equal dimensions to the final insert used. The insert dock  202  allows standardization on a single sensing module  200  for different prosthetic platforms. Thus, the sensing module  200  is common to the different insert docks  202  allowing improved quality, reliability, and performance. 
     In one embodiment, one or more insert docks  202  are used to measure, a force, pressure or load in one or more compartments of the knee having the selected predetermined height or thickness. The surgeon determines an appropriate thickness for the final insert that yields an optimal loading and balance. In general, the absolute loading over the range of motion is kept within a predetermined range. The insert dock  202  and sensing module  200  can be removed from the joint if the absolute loading is found to be above or below the predetermined range. The sensing module  200  is removed from the dock  202  and another selected having a different height. The sensing module  200  is reused and placed in the newly selected dock  202  having a different height or thickness. The dock  202  is then inserted into the knee joint. Measurements are taken to determine if the force, pressure, or load applied by the knee is within the predetermined range. 
     Once the measurements indicate that the measured loading is within the predetermined range, soft tissue tensioning can be used to adjust the absolute loading. The knee balance can also be adjusted within a predetermined range if a total knee reconstruction is being performed and a sensing module  202  is used in each compartment. The position or location where the applied force, pressure, or loading occurs can also be measured by sensing module  200  allowing adjustment over the range of motion. Tibial prosthetic component  106  and device  100  have a combined thickness that represents a combined thickness of tibial prosthetic component  106  and a final (or chronic) insert of the knee joint. Thus, the final insert thickness or depth is chosen based on the trial performed using device  100 . Typically, the final insert thickness is identical to the device  100  to maintain the measured loading and balance. In one embodiment, sensing module  200  and insert docks  202  are disposed of after surgery. Alternatively, the sensing module  200  and insert docks  202  can be cleaned, sterilized, and packaged for reuse. 
     The prosthesis incorporating device  100  emulates the function of a natural knee joint. Device  100  can measure loads or other parameters at various points throughout the range of motion. Data from device  100  is transmitted to a receiving station  110  via wired or wireless communications. In one embodiment, the surgeon can view the transmitted information on a display. The affect of adjustments made by the surgeon can be viewed in real time with the measurements provided by sensing module  200 . The dock  202  and sensing module  200  is removed after the measurements indicate that the force, pressure, or loading is correct, the knee is in balance, and the contact to the insert is centered throughout the range of motion. The final insert is then installed. The final insert will have substantially equal dimensions as the trial insert thereby having similar loadings, balance, and centering. In one embodiment, the final insert includes a sensing module  200  for providing parameter measurement data on the joint throughout its usable life. 
     In a first embodiment, device  100  is a disposable system. Device  100  can be disposed of after using the sensing insert device  100  to optimally fit the joint implant. Device  100  is a low cost disposable system that reduces capital costs, operating costs, facilitates rapid adoption of quantitative measurement, and initiates evidentiary based orthopedic medicine. In a second embodiment, a methodology can be put in place to clean and sterilize device  100  for reuse. In a third embodiment, device  100  can be incorporated in a tool instead of being a component of the replacement joint. The tool can be disposable or be cleaned and sterilized for reuse. In a fourth embodiment, device  100  can be a permanent component of the replacement joint. Device  100  can be used to provide both short term and long term post-operative data on the implanted joint. In a fifth embodiment, device  100  can be coupled to the muscular-skeletal system. In all of the embodiments, receiving station  110  can include data processing, storage, or display, or combination thereof and provide real time graphical representation of the level and distribution of the load. Receiving station  110  can record and provide accounting information of device  100  to an appropriate authority. 
     The sensing insert device  100 , in one embodiment, comprises a load sensing platform  121 , an accelerometer  122 , and sensing assemblies  123 . This permits the sensing device  100  to assess a total load on the prosthetic components when it is being moved. The system accounts for forces due to gravity and motion. In one embodiment, load sensing platform  121  includes two or more load bearing surfaces, at least one energy transducer, at least one compressible energy propagating structure, and at least one member for elastic support. The accelerometer  122  can measure acceleration. Acceleration can occur when the sensing device  100  is moved or put in motion. Accelerometer  122  can sense orientation, vibration, and impact. In another embodiment, the femoral component  104  can similarly include an accelerometer  135 , which by way of a communication interface to the sensing insert device  100 , can provide reference position and acceleration data to determine an exact angular relationship between the femur and tibia. The sensing assemblies  123  can reveal changes in length or compression of the energy propagating structure or structures by way of the energy transducer or transducers. Together the load sensing platform  121 , accelerometer  122  (and in certain cases accelerometer  135 ), and sensing assemblies  123  measure force or pressure external to the load sensing platform  121  or displacement produced by contact with the prosthetic components. 
     In at least one exemplary embodiment, an energy pulse is directed within one or more waveguides in device  100  by way of pulse mode operations and pulse shaping. The waveguide is a conduit that directs the energy pulse in a predetermined direction. The energy pulse is typically confined within the waveguide. In one embodiment, the waveguide comprises a polymer material. For example, urethane or polyethylene are polymers suitable for forming a waveguide. The polymer waveguide can be compressed and has little or no hysteresis in the system. Alternatively, the energy pulse can be directed through the muscular-skeletal system. In one embodiment, the energy pulse is directed through bone of the muscular-skeletal system to measure bone density. A transit time of an energy pulse is related to the material properties of a medium through which it traverses. This relationship is used to generate accurate measurements of parameters such as distance, weight, strain, pressure, wear, vibration, viscosity, and density to name but a few. 
     Incorporating data from the accelerometer  122  with data from the other sensing components  121  and  123  assures accurate measurement of the applied load, force, pressure, or displacement by enabling computation of adjustments to offset this external motion. This capability can be required in situations wherein the body, instrument, appliance, vehicle, equipment, or other physical system, is itself operating or moving during sensing of load, pressure, or displacement. This capability can also be required in situations wherein the body, instrument, appliance, vehicle, equipment, or other physical system, is causing the portion of the body, instrument, appliance, vehicle, equipment, or other physical system being measured to be in motion during sensing of load, pressure, or displacement. 
     The accelerometer  122  can operate singly, as an integrated unit with the load sensing platform  121 , and/or as an integrated unit with the sensing assemblies  123 . Integrating one or more accelerometers  122  within the sensing assemblages  123  to determine position, attitude, movement, or acceleration of sensing assemblages  123  enables augmentation of presentation of data to accurately identify, but not limited to, orientation or spatial distribution of load, force, pressure, displacement, density, or viscosity, or localized temperature by controlling the load and position sensing assemblages to measure the parameter or parameters of interest relative to specific orientation, alignment, direction, or position as well as movement, rotation, or acceleration along any axis or combination of axes. Measurement of the parameter or parameters of interest may also be made relative to the earth&#39;s surface and thus enable computation and presentation of spatial distributions of the measured parameter or parameters relative to this frame of reference. 
     In one embodiment, the accelerometer  122  includes direct current (DC) sensitivity to measure static gravitational pull with load and position sensing assemblages to enable capture of, but not limited to, distributions of load, force, pressure, displacement, movement, rotation, or acceleration by controlling the sensing assemblages to measure the parameter or parameters of interest relative to orientations with respect to the earths surface or center and thus enable computation and presentation of spatial distributions of the measured parameter or parameters relative to this frame of reference. 
     Embodiments of device  100  are broadly directed to measurement of physical parameters, and more particularly, to evaluating changes in the transit time of a pulsed energy wave propagating through a medium. In-situ measurements during orthopedic joint implant surgery would be of substantial benefit to verify an implant is in balance and under appropriate loading or tension. In one embodiment, the instrument is similar to and operates familiarly with other instruments currently used by surgeons. This will increase acceptance and reduce the adoption cycle for a new technology. The measurements will allow the surgeon to ensure that the implanted components are installed within predetermined ranges that maximize the working life of the joint prosthesis and reduce costly revisions. Providing quantitative measurement and assessment of the procedure using real-time data will produce results that are more consistent. A further issue is that there is little or no implant data generated from the implant surgery, post-operatively, and long term. Device  100  can provide implant status data to the orthopedic manufacturers and surgeons. Moreover, data generated by direct measurement of the implanted joint itself would greatly improve the knowledge of implanted joint operation and joint wear thereby leading to improved design and materials. 
     As mentioned previously, device  100  can be used for other joint surgeries; it is not limited to knee replacement implant or implants. Moreover, device  100  is not limited to trial measurements. Device  100  can be incorporated into the final joint system to provide data post-operatively to determine if the implanted joint is functioning correctly. Early determination of a problem using device  100  can reduce catastrophic failure of the joint by bringing awareness to a problem that the patient cannot detect. The problem can often be rectified with a minimal invasive procedure at lower cost and stress to the patient. Similarly, longer term monitoring of the joint can determine wear or misalignment that if detected early can be adjusted for optimal life or replacement of a wear surface with minimal surgery thereby extending the life of the implant. In general, device  100  can be shaped such that it can be placed or engaged or affixed to or within load bearing surfaces used in many orthopedic applications (or used in any orthopedic application) related to the musculoskeletal system, joints, and tools associated therewith. Device  100  can provide information on a combination of one or more performance parameters of interest such as wear, stress, kinematics, kinetics, fixation strength, ligament balance, anatomical fit and balance. 
       FIG. 3  is a perspective view of a medical sensing platform comprising an encapsulating enclosure in accordance with one embodiment. In general, parameters of the muscular-skeletal system can be measured with a sensing module  200  that in one embodiment is an integral part of a complete sensing insert device  100 . The sensing module  200  is a self-contained sensor within an encapsulating enclosure that integrates sensing assemblages, an electronic assemblage that couples to the sensing assemblages, a power source, signal processing, and wireless communication. All components required for the measurement are contained in the sensing module  200 . The sensing module  200  has at least one contacting surface for coupling to the muscular-skeletal system. A parameter of the muscular-skeletal system is applied to the contact surfaces to be measured by the one or more sensing assemblages therein. As will be disclosed in further detail herein, the sensing module  200  is part of a system that allows intra-operative and post-operative sensing of a joint of the muscular-skeletal system. More specifically, sensing module  200  is placed within a temporary or permanent prosthetic component that has a similar form factor as the passive prosthetic component currently being used. This has a benefit of rapid adoption because the sensing platform is inserted identically to the commonly used passive component but can provide much needed quantitative measurements with little or no procedural changes. 
     As shown, the sensing insert device  100  comprises an insert dock  202  and the sensing module  200 . Sensing insert device  100  is a non-permanent or temporary measurement device that is used intra-operatively to provide quantitative data related to the installation of prosthetic components such as in joint replacement surgery. The combination of the insert dock  202  and sensing module  202  has a form factor substantially equal to a final insert device. The final insert device can be a passive component or sensored incorporating sensing module  200 . The substantially equal form factor of sensing insert device  100  results in no extraneous structures in the surgical field that can interfere with the procedure. For example, a final insert device is designed to mimic the function of the natural component it is replacing. The final insert device allows natural movement of the muscular-skeletal system and does not interfere with ligaments, tendons, tissue, muscles, and other components of the muscular-skeletal system. Similarly, sensing insert device  100  allows exposure of the surgical field around the joint by having the similar form factor as the final insert thereby allowing the surgeon to make adjustments during the installation in a natural setting with quantitative measurements to support the modifications. 
     In one embodiment, insert dock  202  is an adaptor. Insert dock  202  is made in different sizes. In general, prosthetic components are manufactured in different sizes to accommodate variation in the muscular-skeletal system from person to person. In the example, the size of insert dock  202  is chosen to mate with the selected prosthetic implant components. In particular, a feature  204  aligns with and retains insert dock  202  in a fixed position to a prosthetic or natural component of the muscular-skeletal system. The insert dock  202  is a passive component having an opening for receiving sensing module  200 . The opening is positioned to place the contacting surfaces in a proper orientation to measure the parameter when used in conjunction with other prosthetic components. The insert dock  202  as an adaptor can be manufactured at low cost. Moreover, insert dock  202  can be formed for adapting to different prosthetic manufacturers thereby increasing system flexibility. This allows a standard sensing module  200  to be provided but customized for appropriate size and dimensions through dock  202  for the specific application and manufacturer component. 
     The one or more sensing assemblages within sensing module  200  couple to the contacting surfaces of sensing module  200  for receiving the applied parameter of the muscular-skeletal system. In one embodiment, a sensing assemblage comprises one or more energy transducers coupled to an elastic structure. The elastic structure allows the propagation of energy waves. The forms of energy propagated through the elastic energy propagating structures may include, but is not limited to, sound, ultrasound, or electromagnetic radiation including radio frequency, infrared, or light. A change in the parameter applied to the contacting surfaces results in a change a dimension of the elastic structure. The dimension of the elastic structure can be measured precisely using continuous wave, pulsed, or pulsed echo measurement. The dimension and material properties of the elastic structure have a known relationship to the parameter being measured. Thus, the dimension is precisely measured and converted to the parameter. Other factors such as movement or acceleration can be taken into account in the calculation. As an example, a force, pressure, or load applied to the one or more contacting surfaces of sensing module  200  is used to illustrate a parameter measurement hereinbelow. It should be noted that this is for illustration purposes and that the sensing module  200  can be used to measure other parameters. 
     As will be shown ahead, the encapsulating enclosure can serve in a first embodiment as a trial implant for orthopedic surgical procedures, namely, for determining load forces on prosthetic components and the musculoskeletal system. In a second embodiment, the encapsulating enclosure can be placed within a permanent prosthetic component for long term monitoring. The encapsulating enclosure supports and protects internal mechanical and electronic components from external physical, mechanical, chemical, and electrical, and electromagnetic intrusion that might compromise sensing or communication operations of the module or device. The integration of the internal components is designed to minimize adverse physical, mechanical, electrical, and ultrasonic interactions that might compromise sensing or communication operations of the module or device. 
       FIG. 4  is a perspective view of a medical sensing device suitable for use as a bi-compartmental implant and comprising an encapsulating enclosure in accordance with one embodiment. As shown, the sensing insert device  100  comprises two sensing modules  200 . Each sensing module  200  is a self-contained encapsulated enclosure that can make individual or coordinated parameter measurements. For example, the sensing insert device  100  can be used to assess load forces on a bi-compartmental knee joint implant. In particular, both sensing modules  200  can individually, or in combination, report applied loading forces. Bi-compartmental sensing provides the benefit of providing quantitative measurement to balance each compartment in relation to one another. 
     Similar to that described above, insert dock  202  is an adaptor having two openings instead of one. Insert dock  202  can be made in different sizes to accommodated different sized prosthetic components and different manufacturers. The insert dock  202  with two openings is a passive component for receiving two separate sensing modules  200 . The opening is positioned to place the contacting surfaces in a proper orientation to measure the parameter when used in conjunction with other prosthetic components. In general, encapsulated enclosures can be positioned on or within, or engaged with, or attached or affixed to or within, a wide range of physical systems including, but not limited to instruments, appliances, vehicles, equipments, or other physical systems as well as animal and human bodies, for sensing and communicating the parameter or parameters of interest in real time. Similar to that described above, insert dock  202  as an adaptor can be manufactured at low cost providing design flexibility and allowing rapid adoption of quantitative measurement. 
       FIG. 5  is an exemplary block diagram of the components of the sensing module  200  in accordance with an exemplary embodiment. It should be noted that the sensing module could comprise more or less than the number of components shown. As illustrated, the sensing module includes one or more sensing assemblages  303 , a transceiver  320 , an energy storage  330 , electronic circuitry  307 , one or more mechanical supports  315  (e.g., springs), and an accelerometer  302 . In the non-limiting example, an applied compressive force can be measured by the sensing module. 
     The sensing assemblage  303  can be positioned, engaged, attached, or affixed to the contact surfaces  306 . Mechanical supports  315  serve to provide proper balancing of contact surfaces  306 . In at least one exemplary embodiment, contact surfaces  306  are load-bearing surfaces. In general, the propagation structure  305  is subject to the parameter being measured. Surfaces  306  can move and tilt with changes in applied load; actions which can be transferred to the sensing assemblages  303  and measured by the electronic circuitry  307 . The electronic circuitry  307  measures physical changes in the sensing assemblage  303  to determine parameters of interest, for example a level, distribution and direction of forces acting on the contact surfaces  306 . In general, the sensing module is powered by the energy storage  330 . 
     As one example, the sensing assemblage  303  can comprise an elastic or compressible propagation structure  305  between a transducer  304  and a transducer  314 . In the current example, transducer  304  can be an ultrasound (or ultrasonic) resonator, and the elastic or compressible propagation structure  305  can be an ultrasound (or ultrasonic) waveguide (or waveguides). The electronic circuitry  307  is electrically coupled to the sensing assemblages  303  and translates changes in the length (or compression or extension) of the sensing assemblages  303  to parameters of interest, such as force. It measures a change in the length of the propagation structure  305  (e.g., waveguide) responsive to an applied force and converts this change into electrical signals which can be transmitted via the transceiver  320  to convey a level and a direction of the applied force. In other arrangements herein contemplated, the sensing assemblage  303  may require only a single transducer. In yet other arrangements, the sensing assemblage  303  can include piezoelectric, capacitive, optical or temperature sensors or transducers to measure the compression or displacement. It is not limited to ultrasonic transducers and waveguides. 
     The accelerometer  302  can measure acceleration and static gravitational pull. Accelerometer  302  can be single-axis and multi-axis accelerometer structures that detect magnitude and direction of the acceleration as a vector quantity. Accelerometer  302  can also be used to sense orientation, vibration, impact and shock. The electronic circuitry  307  in conjunction with the accelerometer  302  and sensing assemblies  303  can measure parameters of interest (e.g., distributions of load, force, pressure, displacement, movement, rotation, torque and acceleration) relative to orientations of the sensing module with respect to a reference point. In such an arrangement, spatial distributions of the measured parameters relative to a chosen frame of reference can be computed and presented for real-time display. 
     The transceiver  320  comprises a transmitter  309  and an antenna  310  to permit wireless operation and telemetry functions. In various embodiments, the antenna  310  can be configured by design as an integrated loop antenna. As will be explained ahead, the integrated loop antenna is configured at various layers and locations on the electronic substrate with electrical components and by way of electronic control circuitry to conduct efficiently at low power levels. Once initiated the transceiver  320  can broadcast the parameters of interest in real-time. The telemetry data can be received and decoded with various receivers, or with a custom receiver. The wireless operation can eliminate distortion of, or limitations on, measurements caused by the potential for physical interference by, or limitations imposed by, wiring and cables connecting the sensing module with a power source or with associated data collection, storage, display equipment, and data processing equipment. 
     The transceiver  320  receives power from the energy storage  330  and can operate at low power over various radio frequencies by way of efficient power management schemes, for example, incorporated within the electronic circuitry  307 . As one example, the transceiver  320  can transmit data at selected frequencies in a chosen mode of emission by way of the antenna  310 . The selected frequencies can include, but are not limited to, ISM bands recognized in International Telecommunication Union regions 1, 2 and 3. A chosen mode of emission can be, but is not limited to, Gaussian Frequency Shift Keying, (GFSK), Amplitude Shift Keying (ASK), Phase Shift Keying (PSK), Minimum Shift Keying (MSK), Frequency Modulation (FM), Amplitude Modulation (AM), or other versions of frequency or amplitude modulation (e.g., binary, coherent, quadrature, etc.). 
     The antenna  310  can be integrated with components of the sensing module to provide the radio frequency transmission. The substrate for the antenna  310  and electrical connections with the electronic circuitry  307  can further include a matching network. This level of integration of the antenna and electronics enables reductions in the size and cost of wireless equipment. Potential applications may include, but are not limited to any type of short-range handheld, wearable, or other portable communication equipment where compact antennas are commonly used. This includes disposable modules or devices as well as reusable modules or devices and modules or devices for long-term use. 
     The energy storage  330  provides power to electronic components of the sensing module. It can be charged by wired energy transfer, short-distance wireless energy transfer or a combination thereof. External power sources can include, but are not limited to, a battery or batteries, an alternating current power supply, a radio frequency receiver, an electromagnetic induction coil, a photoelectric cell or cells, a thermocouple or thermocouples, or an ultrasound transducer or transducers. By way of the energy storage  330 , the sensing module can be operated with a single charge until the internal energy is drained. It can be recharged periodically to enable continuous operation. The energy storage  330  can utilize power management technologies such as replaceable batteries, supply regulation technologies, and charging system technologies for supplying energy to the components of the sensing module to facilitate wireless applications. 
     The energy storage  330  minimizes additional sources of energy radiation required to power the sensing module during measurement operations. In one embodiment, as illustrated, the energy storage  330  can include a capacitive energy storage device  308  and an induction coil  311 . External source of charging power can be coupled wirelessly to the capacitive energy storage device  308  through the electromagnetic induction coil or coils  311  by way of inductive charging. The charging operation can be controlled by power management systems designed into, or with, the electronic circuitry  307 . As one example, during operation of electronic circuitry  307 , power can be transferred from capacitive energy storage device  308  by way of efficient step-up and step-down voltage conversion circuitry. This conserves operating power of circuit blocks at a minimum voltage level to support the required level of performance. 
     In one configuration, the energy storage  330  can further serve to communicate downlink data to the transceiver  320  during a recharging operation. For instance, downlink control data can be modulated onto the energy source signal and thereafter demodulated from the induction coil  311  by way of electronic control circuitry  307 . This can serve as a more efficient way for receiving downlink data instead of configuring the transceiver  320  for both uplink and downlink operation. As one example, downlink data can include updated control parameters that the sensing module uses when making a measurement, such as external positional information, or for recalibration purposes, such as spring biasing. It can also be used to download a serial number or other identification data. 
     The electronic circuitry  307  manages and controls various operations of the components of the sensing module, such as sensing, power management, telemetry, and acceleration sensing. It can include analog circuits, digital circuits, integrated circuits, discrete components, or any combination thereof. In one arrangement, it can be partitioned among integrated circuits and discrete components to minimize power consumption without compromising performance. Partitioning functions between digital and analog circuit enhances design flexibility and facilitates minimizing power consumption without sacrificing functionality or performance. Accordingly, the electronic circuitry  307  can comprise one or more Application Specific Integrated Circuit (ASIC) chips, for example, specific to a core signal processing algorithm. 
     In another arrangement, the electronic circuitry can comprise a controller such as a programmable processor, a Digital Signal Processor (DSP), a microcontroller, or a microprocessor, with associated storage memory and logic. The controller can utilize computing technologies with associated storage memory such a Flash, ROM, RAM, SRAM, DRAM or other like technologies for controlling operations of the aforementioned components of the sensing module. In one arrangement, the storage memory may store one or more sets of instructions (e.g., software) embodying any one or more of the methodologies or functions described herein. The instructions may also reside, completely or at least partially, within other memory, and/or a processor during execution thereof by another processor or computer system. 
     The electronics assemblage also supports testability and calibration features that assure the quality, accuracy, and reliability of the completed wireless sensing module or device. A temporary bi-directional interconnect assures a high level of electrical observability and controllability of the electronics. The test interconnect also provides a high level of electrical observability of the sensing subsystem, including the transducers, waveguides, and mechanical spring or elastic assembly. Carriers or fixtures emulate the final enclosure of the completed wireless sensing module or device during manufacturing processing thus enabling capture of accurate calibration data for the calibrated parameters of the finished wireless sensing module or device. These calibration parameters are stored within the on-board memory integrated into the electronics assemblage. 
     Applications for sensing module  200  may include, but are not limited to, disposable modules or devices as well as reusable modules or devices and modules or devices for long-term use. In addition to non-medical applications, examples of a wide range of potential medical applications may include, but are not limited to, implantable devices, modules within implantable devices, intra-operative implants or modules within intra-operative implants or trial inserts, modules within inserted or ingested devices, modules within wearable devices, modules within handheld devices, modules within instruments, appliances, equipment, or accessories of all of these, or disposables within implants, trial inserts, inserted or ingested devices, wearable devices, handheld devices, instruments, appliances, equipment, or accessories to these devices, instruments, appliances, or equipment. 
       FIG. 6  is a diagram of an exemplary communications system  400  for short-range telemetry according to one embodiment. As illustrated, the exemplary communications system  400  comprises medical device communications components  410  of the sensing insert device  100  (see  FIG. 1 ) and receiving system communications components  450  of the receiving system  110  (see  FIG. 1 ). The medical device communications components  410  are inter-operatively coupled to include, but not limited to, the antenna  412 , a matching network  414 , the telemetry transceiver  416 , a CRC circuit  418 , a data packetizer  422 , a data input  424 , a power source  426 , and an application specific integrated circuit (ASIC)  420 . The medical device communications components  410  may include more or less than the number of components shown and are not limited to those shown or the order of the components. 
     The receiving station communications components  450  comprise an antenna  452 , the matching network  454 , the telemetry receiver  456 , the CRC circuit  458 , the data packetizer  460 , and optionally a USB interface  462 . Notably, other interface systems can be directly coupled to the data packetizer  460  for processing and rendering sensor data. 
     With respect to  FIG. 1 , in view of the communication components of  FIG. 6 , the sensing insert device  100  acquires sensor data by way of the data input to the ASIC  420 . Referring briefly to  FIG. 5 , the ASIC  420  is operatively coupled to sensing assemblies  303 . In one embodiment, a change in the parameter being measured by device  100  produces a change in a length of a compressible propagation structure  305 . ASIC  420  controls the emission of energy waves into propagation structure  305  and the detection of propagated energy waves. ASIC  420  generates data related to transit time, frequency, or phase of propagated energy waves. The data corresponds to the length of propagation structure  305 , which can be translated to the parameter of interest by way of a known function or relationship. Similarly, the data can comprise voltage or current measurements from a MEMS structure, piezo-resistive sensor, strain gauge, or other sensor type that is used to measure the parameter. The data packetizer  422  assembles the sensor data into packets; this includes sensor information received or processed by ASIC  420 . The ASIC  420  can comprise specific modules for efficiently performing core signal processing functions of the medical device communications components  410 . The ASIC  420  provides the further benefit of reducing the form factor of sensing insert device  100  to meet dimensional requirements for integration into temporary or permanent prosthetic components. 
     The CRC circuit  418  applies error code detection on the packet data. The cyclic redundancy check is based on an algorithm that computes a checksum for a data stream or packet of any length. These checksums can be used to detect interference or accidental alteration of data during transmission. Cyclic redundancy checks are especially good at detecting errors caused by electrical noise and therefore enable robust protection against improper processing of corrupted data in environments having high levels of electromagnetic activity. The telemetry transmitter  416  then transmits the CRC encoded data packet through the matching network  414  by way of the antenna  412 . The matching networks  414  and  454  provide an impedance match for achieving optimal communication power efficiency. 
     The receiving system communications components  450  receive transmission sent by medical device communications components  410 . In one embodiment, telemetry transmitter  416  is operated in conjunction with a dedicated telemetry receiver  456  that is constrained to receive a data stream broadcast on the specified frequencies in the specified mode of emission. The telemetry receiver  456  by way of the receiving station antenna  452  detects incoming transmissions at the specified frequencies. The antenna  452  can be a directional antenna that is directed to a directional antenna of components  410 . Using at least one directional antenna can reduce data corruption while increasing data security by further limiting where the data is radiated. A matching network  454  couples to antenna  452  to provide an impedance match that efficiently transfers the signal from antenna  452  to telemetry receiver  456 . Telemetry receiver  456  can reduce a carrier frequency in one or more steps and strip off the information or data sent by components  410 . Telemetry receiver  456  couples to CRC circuit  458 . CRC circuit  458  verifies the cyclic redundancy checksum for individual packets of data. CRC circuit  458  is coupled to data packetizer  460 . Data packetizer  460  processes the individual packets of data. In general, the data that is verified by the CRC circuit  458  is decoded (e.g., unpacked) and forwarded to an external data processing device, such as an external computer, for subsequent processing, display, or storage or some combination of these. 
     The telemetry receiver  456  is designed and constructed to operate on very low power such as, but not limited to, the power available from the powered USB port  462 , or a battery. In another embodiment, the telemetry receiver  456  is designed for use with a minimum of controllable functions to limit opportunities for inadvertent corruption or malicious tampering with received data. The telemetry receiver  456  can be designed and constructed to be compact, inexpensive, and easily manufactured with standard manufacturing processes while assuring consistently high levels of quality and reliability. 
     In one configuration, the communication system  400  operates in a transmit-only operation with a broadcasting range on the order of a few meters to provide high security and protection against any form of unauthorized or accidental query. The transmission range can be controlled by the transmitted signal strength, antenna selection, or a combination of both. A high repetition rate of transmission can be used in conjunction with the Cyclic Redundancy Check (CRC) bits embedded in the transmitted packets of data during data capture operations thereby enabling the receiving system  110  to discard corrupted data without materially affecting display of data or integrity of visual representation of data, including but not limited to measurements of load, force, pressure, displacement, flexion, attitude, and position within operating or static physical systems. 
     By limiting the operating range to distances on the order of a few meters the telemetry transmitter  416  can be operated at very low power in the appropriate emission mode or modes for the chosen operating frequencies without compromising the repetition rate of the transmission of data. This mode of operation also supports operation with compact antennas, such as an integrated loop antenna. The combination of low power and compact antennas enables the construction of, but is not limited to, highly compact telemetry transmitters that can be used for a wide range of non-medical and medical applications. Examples of potential medical applications may include, but are not limited to, implantable devices, modules within implantable devices, intra-operative implants or modules within intra-operative implants or trial inserts, modules within inserted or ingested devices, modules within wearable devices, modules within handheld devices, modules within instruments, appliances, equipment, or accessories of all of these, or disposables within implants, trial inserts, inserted or ingested devices, wearable devices, handheld devices, instruments, appliances, equipment, or accessories to these devices, instruments, appliances, or equipment. 
     The transmitter security as well as integrity of the transmitted data is assured by operating the telemetry system within predetermined conditions. The security of the transmitter cannot be compromised because it is operated in a transmit-only mode and there is no pathway to hack into medical device communications components  410 . The integrity of the data is assured with the use of the CRC algorithm and the repetition rate of the measurements. The risk of unauthorized reception of the data is minimized by the limited broadcast range of the device. Even if unauthorized reception of the data packets should occur there are counter measures in place that further mitigate data access. A first measure is that the transmitted data packets contain only binary bits from a counter along with the CRC bits. A second measure is that no data is available or required to interpret the significance of the binary value broadcast at any time. A third measure that can be implemented is that no patient or device identification data is broadcast at any time. 
     The telemetry transmitter  416  can also operate in accordance with some FCC regulations. According to section 18.301 of the FCC regulations the ISM bands within the USA include 6.78, 13.56, 27.12, 30.68, 915, 2450, and 5800 MHz as well as 24.125, 61.25, 122.50, and 245 GHz. Globally other ISM bands, including 433 MHz, are defined by the International Telecommunications Union in some geographic locations. The list of prohibited frequency bands defined in 18.303 are “the following safety, search and rescue frequency bands is prohibited: 490-510 kHz, 2170-2194 kHz, 8354-8374 kHz, 121.4-121.6 MHz, 156.7-156.9 MHz, and 242.8-243.2 MHz.” Section 18.305 stipulates the field strength and emission levels ISM equipment must not exceed when operated outside defined ISM bands. In summary, it may be concluded that ISM equipment may be operated worldwide within ISM bands as well as within most other frequency bands above 9 KHz given that the limits on field strengths and emission levels specified in section 18.305 are maintained by design or by active control. As an alternative, commercially available ISM transceivers, including commercially available integrated circuit ISM transceivers, may be designed to fulfill these field strengths and emission level requirements when used properly. 
     In one configuration, the telemetry transmitter  416  can also operate in unlicensed ISM bands or in unlicensed operation of low power equipment, wherein the ISM equipment (e.g., telemetry transmitter  416 ) may be operated on ANY frequency above 9 kHz except as indicated in Section 18.303 of the FCC code. 
     Wireless operation eliminates distortion of, or limitations on, measurements caused by the potential for physical interference by, or limitations imposed by, wiring and cables connecting the wireless sensing module or device with a power source or with data collection, storage, or display equipment. Power for the sensing components and electronic circuits is maintained within the wireless sensing module or device on an internal energy storage device. This energy storage device is charged with external power sources including, but not limited to, a battery or batteries, super capacitors, capacitors, an alternating current power supply, a radio frequency receiver, an electromagnetic induction coil, a photoelectric cell or cells, a thermocouple or thermocouples, or an ultrasound transducer or transducers. The wireless sensing module may be operated with a single charge until the internal energy source is drained or the energy source may be recharged periodically to enable continuous operation. The embedded power supply minimizes additional sources of energy radiation required to power the wireless sensing module or device during measurement operations. Telemetry functions are also integrated within the wireless sensing module or device. Once initiated the telemetry transmitter continuously broadcasts measurement data in real time. Telemetry data may be received and decoded with commercial receivers or with a simple, low cost custom receiver. 
     A method can be practiced with more or less than the number of steps shown and is not limited to the order shown. To describe the method, reference will be made to the components of  FIG. 5 , although it is understood that the method can be implemented in any other manner using other suitable components. Generally, method is directed to non-secure applications for one-way transmission communications, for example, where an implanted medical device or sensor transmits data to a receiving station (e.g.,  110  see  FIG. 1 ) but does not receive confirmation from the receiving station, although in various embodiments, the implanted medical device includes an integrated receiver for receiving confirmation and acknowledgement communications. 
     The method can start in a state wherein the sensing insert device  100  has been inserted and powered on, for example, within a knee prosthesis implant. The medical device can be powered on via manual intervention, for example, by the surgeon or technician implanting the medical device during a surgical procedure, or the device can turn on automatically after a duration of time or at certain time intervals, for example, 1 hour after manual activation, or every 10 seconds after power up, depending on an operating mode. 
     In a first step, the medical device acquires sensor data such as load information (e.g., force, location, duration, etc.) from the sensing module  200 . The electronic circuitry  307  generates the load data by way of the sensing assemblies  303 , for instance, by converting changes in length of ultrasonic propagation structures (waveguides) to force data. In a second step, the sensing module  200  evaluates data bounds on the load data. In a third step, sensing module  200  assigns priorities based on the data bounds. Sensor data outside a predetermined range or above a predefined threshold can be flagged with a priority or discarded. For example, sensor data that falls outside a safe range or exceeds a safe level (e.g., applied force level, angle of flexion, excessive rotation) is prioritized accordingly. 
     In a fourth step, the sensing module  200  generates a packet of data including the sensor data, priority, and any corresponding information. In a fifth step, the sensing module  200  determines its communications mode based on operating mode and priority level. The operating mode indicates whether the sensing module  200  is operating in a power saving mode (e.g., standby) or other power management mode and takes into account information such as remaining battery life and drain. In a sixth step, a Cyclic Redundancy Check (CRC) can be appended to the data packed. In other embodiments, more sophisticated forward error correction schemes (e.g., block coding, convolutional coding) can be applied along with secure encryption or key-exchange cryptographic protocols. 
     The cyclic redundancy check (CRC) is a non-secure form of message digest designed to detect accidental changes to raw computer data. The CRC step comprises calculating a short, fixed-length sequence, known as the CRC code, for each block of data and sends or stores them both together. When a block is read or received the receiving station  110  ( FIG. 1 ) repeats the calculation; if the new CRC does not match the one sent (or in some cases, cancel it out) then the block contains a data error and the receiving station  110  may take corrective action such as rereading or requesting the block be sent again. Briefly,  FIG. 13 , illustrates an exemplary data packet  1300  containing sensor data (e.g., Fx, duration, location), a priority level (e.g., 1 to 10), and a CRC. 
     In a seventh step, the transceiver  320  then transmits the data packet based on the priority level and operating mode. For instance, a low priority data packet can be appended with previous low-priority data packets and then transmitted over a single communication channel as a data stream, or at staggered time intervals to conserve power (e.g., scheduled to transmit every 10 seconds). The bundled packet data can then be decoded at the receiving station  110  and thereafter processed accordingly. Alternatively, a high priority packet can be transmitted immediately instead of a delayed time or the scheduled transmit intervals. Depending on the communication mode (e.g., priority level, operating mode), the transceiver may transmit the same high priority packet multiple times in a redundant manner to guarantee receipt. This ensures that the data is received and processed at the receiving station  110  in the event an immediate course of action or response is necessary, for example, to ensure the patient&#39;s safety or to report a warning. 
     The sensor data can be transmitted at the selected frequencies in the chosen mode of emission by way of the antenna  310 . In certain configurations, the antenna  310  is an integrated loop antenna designed into a substrate of the sensing module  200  for maximizing power efficiency. As an example the chosen frequencies can include, but are not limited to, ISM bands recognized in International Telecommunication Union regions 1, 2, and 3 and the chosen mode of emission may be, but is not limited to, Gaussian Frequency Shift Keying, (GFSK) or others version of frequency or amplitude shift keying or modulation. 
     The receiving station  110  (see  FIG. 1 )  110  receives packets of data broadcast in the specified mode of emission on the specified frequencies and verifies the cyclic redundancy check checksum for individual packets of data or bundled packet data. Data that cannot be verified may be discarded. Data that are verified are forward to an external data processing device, such as an external computer, for subsequent processing, display, or storage or combination thereof. 
       FIG. 7  is an illustration of a block model diagram  500  of the sensing module  200  in accordance with an exemplary embodiment. In particular, the diagram  500  shows where certain components are replaced or supplemented with one or more Application Specific Integrated Circuits (ASICs). Referring briefly to  FIG. 5 , electronic circuitry  307  is coupled to the one or more sensing assemblages and includes circuitry that can control sensor operations. Electronic circuitry  307  includes multiple channels that can operate more than one device. Sensing module  200  is optimized to operate under severe power constraints. Electronic circuitry  307  includes power management circuitry that controls power up, power down, and minimizes power usage through the control of individual blocks. The architecture is designed to enable only blocks required for the current operation. 
     Referring back to  FIG. 7 , the ASIC provides significant benefit in reducing power requirements allowing the module  200  to be powered by a temporary power source such as a super capacitor or capacitor. The ASIC and super capacitor have a small form factor allowing module  200  to be integrated within a temporary or permanent prosthetic component. Module  200  incorporates one or more sensors comprising at least one transducer and a compressible media, the operation of which is disclosed in detail herein. As shown, a sensing assemblage comprises a transducer  502 , compressible propagation structure  504 , and a transducer  506 . It should be noted that other sensors such as MEMS devices, strain gauges, and piezo-resistive sensors can be used with the ASIC. In particular, the ASIC incorporates A/D and D/A circuitry (not shown) to digitize current and voltage output from these types of sensing components. Transducers  502  and  506  operatively couple to compressible propagation structure  504 . In a non-limiting example, transducer  506  to emits energy waves into compressible structure  504  while transducer  502  detects propagated energy waves. Compressible propagation structure  504  is coupled to a load bearing or contacting surface  508  and an encapsulating enclosure  510  of sensing module  200 . A parameter to be measured is applied to either contacting surface  508 , encapsulating enclosure  510 , or both. In one embodiment, springs  560  couple to contacting surface  508  and encapsulating enclosure  510  to support compressible propagation structure  504 . In particular, springs  560  prevent cantilevering of contacting surface  508 , reduce hysteresis caused by material properties of compressible propagation structure  504 , and improve sensor response time to changes in the applied parameter. 
     In one embodiment, a first ASIC includes a charging circuit  514  and power management circuitry  518 . The power management circuitry  518  couples to the charging circuit, other blocks of the ASIC and external components/circuitry to minimize power consumption of the integrated circuit. The charging circuit  514  operatively couples to an induction coil  512  and energy storage  516 . In a non-limiting example, induction coil  512  couples to an external coil that provides energy to charge energy storage  516 . Induction coil  512  and the external coil are placed in proximity to each other thereby electro-magnetically coupling to one another. Induction coil  512  is coupled to energy storage  516 . Charging circuit  514  controls the charging of energy storage  516 . Charging circuit  514  can determine when charging is complete, monitor power available, and regulate a voltage provided to the operational circuitry. Charging circuit  514  can charge a battery in sensing module  200 . Alternatively, a capacitor or super capacitor can be used to power the first ASIC for a time sufficient to acquire the desired measurements. A capacitor has the benefit of a long or indefinite shelf life and fast charge time. In either charging scenario, energy from the external coil is coupled to the induction coil  512 . The energy from induction coil  512  is then stored in a medium such as a battery or capacitor. 
     Benefits of ultracapacitors, ultra capacitors, or super capacitors, or other form of capacitors as a power source instead or, or in conjunction with, other power sources or rechargeable technologies include, but are not limited to, enabling a high level of miniaturization as ultracapacitors, ultra capacitors, or super capacitors are smaller than smallest available battery for the same level of energy and power for many low power applications or applications that require power only intermittently or as a short-term backup for other power sources. 
     For applications that require power only intermittently, capacitors enable rapid recharge that is much faster than battery technologies and rechargeable chemistries regardless of their energy capacity. A charge time, from a completely uncharged state takes minutes because no chemical processes are involved in charging capacitors. This may be compared to charge times on the order of hours for many battery technologies that cannot be charged at a rate faster that one-half the energy storage capacity of the battery within one hour. In practice, many battery applications charge at a much slower rate. Many capacitors have the added benefit of almost indefinite lifetimes. There is no deterioration of a capacitor&#39;s storage capacity when uncharged, regardless of length of time at zero charge. Another benefit is that overcharging capacitors may pose less risk to electronics within an electronic module or device than overcharging batteries might pose. Furthermore, capacitors eliminate storage and disposal limitations of batteries with no risk of chemical leakage. In addition, capacitors can have a smaller form factor, are surface-mountable, and integrate well into the electronics assemblies and standard surface-mount electronic assembly processes. 
     Use capacitors to provide operating power for wireless devices, telemetry devices, or medical devices provides design, construction, and operating flexibility over a wide range of potential applications. Capacitors can be charged by connecting them to other power sources such as, but not limited to, a battery or batteries, an alternating current (AC) power supply, a radio frequency (RF) receiver, or an electromagnetic induction coil or coils, a photoelectric cell or cells, a thermocouple or thermocouples, capacitors, or an ultrasound transducer or transducers. For compact electronic modules or devices, ultracapacitors, super capacitors, or other form of capacitors provide many benefits over other rechargeable technologies. 
     The first ASIC further includes circuitry to operate and capture data from the sensing assemblages. A parameter to be measured is applied to compressible propagation structure  504 . As an example of parameter measurement, a force, pressure, or load is applied across contacting surface  508  and encapsulating enclosure  510 . The force, pressure, or load affects the length of the compressible propagation structure  504 . The circuitry on the first ASIC forms a positive closed loop feedback circuit that maintains the emission, propagation, and detection of energy waves in the compressible propagation structure  504 . The first ASIC operatively couples to transducers  502  and  506  to control the positive closed loop feedback circuit that is herein called a propagation tuned oscillator (PTO). The first ASIC measures a transit time, frequency, or phase of propagated energy waves. The measurement is used to determine the length of compressible propagation structure  504 . The energy waves emitted into compressible propagation structure  504  can be continuous or pulsed. The energy waves can propagate by a direct path or be reflected. 
     The first ASIC comprises an oscillator  520 , a switch  522 , driver  524 , matching network  526 , MUX  528 , and control circuit  536 . The oscillator  520  is used as a reference clock for the ASIC and enables the PTO to begin emission of energy waves into the compressible propagation structure  504 . Oscillator  520  in the first ASIC can be coupled to an external component such as a crystal oscillator to define and provide a stable frequency of operation. Switch  522  couples the oscillator  520  to MUX  528 . Control circuit  536  operatively enables MUX  528  and switch  522  to couple oscillator  520  to driver  524  during a startup sequence. Driver  524  and matching network  526  couple to transducer  506 . Driver  524  drives transducer  506  to emit an energy wave. Matching network  526  impedance matches driver  524  to the transducer  506  to reduce power consumption during energy wave emission. 
     In one embodiment, transducer  506  emits one or more energy waves into the compressible propagation structure  504  at a first location. Transducer  506  is located at a second location of compressible propagation structure  504 . Transducer  506  detects propagated energy waves at the second location and generates a signal corresponding to the propagated energy waves. The first ASIC further comprises a MUX  530 , pre-amplifier  532  (e.g. preamp  532 ) and a zero-crossing receiver or edge detect receiver. Zero-crossing receiver or edge-detect receiver comprise detect circuit  534 . Control circuit  536  enables MUX  530  to couple transducer  502  to preamp  532 . Preamp  532  amplifies a signal output by transducer  502  corresponding to a propagated energy wave. In a non-limiting example, the first ASIC comprises both a zero-crossing receiver and an edge detect receiver. More multiplexing circuitry in conjunction with control circuit  536  can be incorporated on the first ASIC to select between the circuits. Similarly, multiplexing circuitry can be used to couple and operate more than one sensor. The amplified signal from preamp  532  is coupled to detection circuit  534 . Zero-crossing receiver is a detection circuit that identifies a propagated energy wave by sensing a transition of the signal. A requirement of detection can be that the signal has certain transition and magnitude characteristics. The edge-detect receiver detects a propagated energy wave by identifying a wave front of the propagated energy wave. The zero-crossing receiver or edge-detect receiver outputs a pulse in response to the detection of a propagated energy wave. 
     Positive closed loop feedback is applied upon detection of an energy wave after the startup sequence. Control circuit  536  decouples oscillator  520  from driver  524  through switch  522  and MUX  528 . Control circuit  536  operatively enables switch  558  and MUX  528  to couple detection circuit  534  to driver  524 . A pulse generated by detection circuit  534  initiates the emission of a new energy wave into compressible propagation structure  504 . The pulse from detection circuit  534  is provided to driver  524 . The positive closed loop feedback of the circuitry maintains the emission, propagation, and detection of energy waves in propagation structure  504 . 
     The first ASIC further comprises a loop counter  538 , time counter  540 , register  542 , and ADC  556 . Loop counter  538 , time counter  540 , and register  542  are operatively coupled to control circuit  536  to generate a precise measurement of the transit time, frequency, or phase of propagated energy waves during a measurement sequence. In one embodiment, a measurement comprises a predetermined number of energy waves propagating through the compressible propagation structure  504 . The predetermined number is set in the loop counter  538 . The loop counter  538  is decremented by each pulse output by detection circuit  534  that corresponds to a detected propagated energy wave. The positive closed loop feedback is broken when counter  538  decrements to zero thereby stopping the measurement. Time counter  540  measures a total propagation time of the predetermined number of propagated energy waves set in loop counter  538 . The measured total propagation time divided by the predetermined number of propagated energy waves is a measured transit time of an energy wave. The measured transit time can be precisely converted to a length of compressible propagation structure  504  under a stable condition of the applied parameter on the sensing assemblage. The applied parameter value can be calculated by known relationship between the length of compressible propagation structure  504  and the parameter. A result of the measurement is stored in register  542  when loop counter  538  decrements to zero. More than one measurement can be performed and stored. In one embodiment, the precision can be increased by raising the number of propagated energy waves being measured in loop counter  538 . 
     In the example, energy waves are propagated from transducer  506  to transducer  5 . Alternatively, control circuit  536  can direct the propagation of energy waves from transducer  502  to transducer  506  whereby transducer  502  emits energy waves and transducer  506  detects propagated energy waves. An analog to digital converter (ADC)  556  is shown coupled to an accelerometer  554 . ADC  556  is a circuit on the first ASIC. It can be used to digitize an output from a circuit such as accelerometer  554 . Accelerometer  554  can be used to detect and measure when sensing module  200  is in motion. Data from accelerometer  554  can be used to correct the measured result to account for module  200  acceleration. ADC  556  can also be used to provide measurement data from other sensor types by providing a digitized output corresponding to voltage or current magnitude. 
     A second ASIC can comprise CRC circuit  546 , telemetry transmitter  548 , and matching network  508 . The CRC circuit  546  applies error code detection on the packet data such as data stored in register  542 . The cyclic redundancy check computes a checksum for a data stream or packet of any length. The checksums are used to detect interference or accidental alteration of data during transmission. Transmitter  548  is coupled to CRC  546  and sends the data wirelessly. Matching network  550  couples telemetry transmitter  512  to antenna  552  to provide an impedance match to efficiently transfer the signal to the antenna  552 . As disclosed above, the integration of the telemetry transmitter and sensor modules enables construction of a wide range of sizes of the sensing module  200 . This facilitates capturing data, measuring parameters of interest and digitizing that data, and subsequently communicating that data to external equipment with minimal disturbance to the operation of the body, instrument, appliance, vehicle, equipment, or physical system for a wide range of applications. Moreover, the level of accuracy and resolution achieved by the total integration of communication components, transducers, waveguides, and oscillators to control the operating frequency of the ultrasound transducers enables the compact, self-contained measurement module construction. In a further embodiment, the circuitry on the first and second ASICs can be combined on a single ASIC to further reduce form factor, power, and cost. 
       FIG. 8  is an exemplary assemblage  800  that illustrates propagation of ultrasound waves  810  within the waveguide  806  in the bi-directional mode of operation of this assemblage. In this mode, the selection of the roles of the two individual ultrasound resonators ( 802 ,  804 ) or transducers affixed to interfacing material  820  and  822 , if required, are periodically reversed. In the bi-directional mode the transit time of ultrasound waves propagating in either direction within the waveguide  806  can be measured. This can enable adjustment for Doppler effects in applications where the sensing module  808  is operating while in motion  816 . Furthermore, this mode of operation helps assure accurate measurement of the applied load, force, pressure, or displacement by capturing data for computing adjustments to offset this external motion  816 . An advantage is provided in situations wherein the body, instrument, appliance, vehicle, equipment, or other physical system  814 , is itself operating or moving during sensing of load, pressure, or displacement. Similarly, the capability can also correct in situation where the body, instrument, appliance, vehicle, equipment, or other physical system, is causing the portion  812  of the body, instrument, appliance, vehicle, equipment, or other physical system being measured to be in motion  816  during sensing of load, force, pressure, or displacement. Other adjustments to the measurement for physical changes to system  814  are contemplated and can be compensated for in a similar fashion. For example, temperature of system  814  can be measured and a lookup table or equation having a relationship of temperature versus transit time can be used to normalize measurements. Differential measurement techniques can also be used to cancel many types of common factors as is known in the art. 
     The use of waveguide  806  enables the construction of low cost sensing modules and devices over a wide range of sizes, including highly compact sensing modules, disposable modules for bio-medical applications, and devices, using standard components and manufacturing processes. The flexibility to construct sensing modules and devices with very high levels of measurement accuracy, repeatability, and resolution that can scale over a wide range of sizes enables sensing modules and devices to the tailored to fit and collect data on the physical parameter or parameters of interest for a wide range of medical and non-medical applications. 
     Referring back to  FIG. 2 , although not explicitly illustrated, it should be noted that the load insert sensing device  100  and associated internal components move in accordance with motion of the femur  108  as shown. The bi-directional operating mode of the waveguide mitigates the Doppler effects resulting from the motion. As previously indicated, incorporating data from the accelerometer  121  with data from the other components of the sensing module  200  helps assure accurate measurement of the applied load, force, pressure, displacement, density, localized temperature, or viscosity by enabling computation of adjustments to offset this external motion. 
     For example, sensing modules or devices may be placed on or within, or attached or affixed to or within, a wide range of physical systems including, but not limited to instruments, appliances, vehicles, equipments, or other physical systems as well as animal and human bodies, for sensing the parameter or parameters of interest in real time without disturbing the operation of the body, instrument, appliance, vehicle, equipment, or physical system. 
     In addition to non-medical applications, examples of a wide range of potential medical applications may include, but are not limited to, implantable devices, modules within implantable devices, modules or devices within intra-operative implants or trial inserts, modules within inserted or ingested devices, modules within wearable devices, modules within handheld devices, modules within instruments, appliances, equipment, or accessories of all of these, or disposables within implants, trial inserts, inserted or ingested devices, wearable devices, handheld devices, instruments, appliances, equipment, or accessories to these devices, instruments, appliances, or equipment. Many physiological parameters within animal or human bodies may be measured including, but not limited to, loading within individual joints, bone density, movement, various parameters of interstitial fluids including, but not limited to, viscosity, pressure, and localized temperature with applications throughout the vascular, lymph, respiratory, and digestive systems, as well as within or affecting muscles, bones, joints, and soft tissue areas. For example, orthopedic applications may include, but are not limited to, load bearing prosthetic components, or provisional or trial prosthetic components for, but not limited to, surgical procedures for knees, hips, shoulders, elbows, wrists, ankles, and spines; any other orthopedic or musculoskeletal implant, or any combination of these. 
       FIG. 9  is an exemplary cross-sectional view of a sensor element  900  to illustrate changes in the propagation of ultrasound waves  914  with changes in the length of a waveguide  906 . In general, the measurement of a parameter is achieved by relating displacement to the parameter. In one embodiment, the displacement required over the entire measurement range is measured in microns. For example, an external force  908  compresses waveguide  906  thereby changing the length of waveguide  906 . Sensing circuitry (not shown) measures propagation characteristics of ultrasonic signals in the waveguide  906  to determine the change in the length of the waveguide  906 . These changes in length change in direct proportion to the parameters of interest thus enabling the conversion of changes in the parameter or parameters of interest into electrical signals. 
     As previously discussed, external forces applied to the sensing module  200  compress the waveguide(s) thereby changing the length of the waveguide(s). The sensing module  200  measures propagation characteristics of ultrasonic signals in the waveguide(s) to determine the change in the length of the waveguide(s). These changes in length change in direct proportion to the parameters of interest thus enabling the conversion of changes in the parameter or parameters of interest into load (or force) information. 
     As illustrated, external force  908  compresses waveguide  906  and pushes the transducers  902  and  904  closer to one another by a distance  910 . This changes the length of waveguide  906  by distance  912  of the waveguide propagation path between transducers  902  and  904 . Depending on the operating mode, the sensing circuitry measures the change in length of the waveguide  906  by analyzing characteristics of the propagation of ultrasound waves within the waveguide. 
     One interpretation of  FIG. 9  illustrates waves emitting from transducer  902  at one end of waveguide  906  and propagating to transducer  904  at the other end of the waveguide  906 . The interpretation includes the effect of movement of waveguide  906  and thus the velocity of waves propagating within waveguide  906  (without changing shape or width of individual waves) and therefore the transit time between transducers  902  and  904  at each end of the waveguide. The interpretation further includes the opposite effect on waves propagating in the opposite direction and is evaluated to estimate the velocity of the waveguide and remove it by averaging the transit time of waves propagating in both directions. 
     Changes in the parameter or parameters of interest are measured by measuring changes in the transit time of energy pulses or waves within the propagating medium. Closed loop measurement of changes in the parameter or parameters of interest is achieved by modulating the repetition rate of energy pulses or the frequency of energy waves as a function of the propagation characteristics of the elastic energy propagating structure. 
     In a continuous wave mode of operation, a phase detector (not shown) evaluates the frequency and changes in the frequency of resonant ultrasonic waves in the waveguide  906 . As will be described below, positive feedback closed-loop circuit operation in continuous wave (CW) mode adjusts the frequency of ultrasonic waves  914  in the waveguide  906  to maintain a same number or integer number of periods of ultrasonic waves in the waveguide  906 . The CW operation persists as long as the rate of change of the length of the waveguide is not so rapid that changes of more than a quarter wavelength occur before the frequency of the propagation tuned oscillator (PTO) can respond. This restriction exemplifies one advantageous difference between the performance of a PTO and a Phase Locked Loop (PLL). Assuming the transducers are producing ultrasonic waves, for example, at 2.4 MHz, the wavelength in air, assuming a velocity of 343 microns per microsecond, is about 143μ, although the wavelength within a waveguide may be longer than in unrestricted air. 
     In a pulse mode of operation, the phase detector measures a time of flight (TOF) between when an ultrasonic pulse is transmitted by transducer  902  and received at transducer  904 . The time of flight determines the length of the waveguide propagating path, and accordingly reveals the change in length of the waveguide  906 . In another arrangement, differential time of flight measurements (or phase differences) can be used to determine the change in length of the waveguide  906 . A pulse consists of a pulse of one or more waves. The waves may have equal amplitude and frequency (square wave pulse) or they may have different amplitudes, for example, decaying amplitude (trapezoidal pulse) or some other complex waveform. The PTO is holding the phase of the leading edge of the pulses propagating through the waveguide constant. In pulse mode operation the PTO detects the leading edge of with an edge-detect receiver rather than a zero-crossing or transition as detected by a zero-crossing receiver used in CW mode. 
     It should be noted that ultrasound energy pulses or waves, the emission of ultrasound pulses or waves by ultrasound resonators or transducers, transmitted through ultrasound waveguides, and detected by ultrasound resonators or transducers are used merely as examples of energy pulses, waves, and propagation structures and media. Other embodiments herein contemplated can utilize other wave forms, such as, light. 
       FIG. 10  is an exemplary block diagram  1000  of a propagation tuned oscillator (PTO)  4  to maintain positive closed-loop feedback in accordance with an exemplary embodiment. The measurement system includes a sensing assemblage  1  and propagation tuned oscillator (PTO)  4  that detects energy waves  2  in one or more waveguides  3  of the sensing assemblage  1 . In one embodiment, energy waves  2  are ultrasound waves. A pulse  11  is generated in response to the detection of energy waves  2  to initiate a propagation of a new energy wave in waveguide  3 . It should be noted that ultrasound energy pulses or waves, the emission of ultrasound pulses or waves by ultrasound resonators or transducers, transmitted through ultrasound waveguides, and detected by ultrasound resonators or transducers are used merely as examples of energy pulses, waves, and propagation structures and media. Other embodiments herein contemplated can utilize other wave forms, such as, light. 
     Recall that the sensing insert device  100  when in motion measures forces on the sensing assemblies by evaluating propagation times of energy waves within the waveguides in conjunction with the accelerometer data. The propagation tuned oscillator (PTO)  4  measures a transit time of ultrasound waves  2  within the waveguide  3  in a closed-loop configuration. The digital counter  20  determines the physical change in the length of the waveguide. Referring to  FIG. 5 , the one or more accelerometers  302  determines the changes along x, y and z dimensions. The electronic circuitry  307  in view of the accelerometer data from accelerometer  302  and the physical changes in length of the sensing assemblage  1  determines the applied loading (or forces). 
     The sensing assemblage  1  comprises transducer  5 , transducer  6 , and a waveguide  3  (or energy propagating structure). In a non-limiting example, sensing assemblage  1  is affixed to load bearing or contacting surfaces  8 . External forces applied to the contacting surfaces  8  compress the waveguide  3  and change the length of the waveguide  3 . Under compression, transducers  5  and  6  will also be moved closer together. The change in distance affects the transit time  7  of energy waves  2  transmitted and received between transducers  5  and  6 . The propagation tuned oscillator  4  in response to these physical changes will detect each energy wave sooner (e.g. shorter transit time) and initiate the propagation of new energy waves associated with the shorter transit time. As will be explained below, this is accomplished by way of PTO  4  in conjunction with the pulse generator  10 , the mode control  12 , and the phase detector  14 . 
     Notably, changes in the waveguide  3  (energy propagating structure or structures) alter the propagation properties of the medium of propagation (e.g. transit time  7 ). The energy wave can be a continuous wave or a pulsed energy wave. A pulsed energy wave approach reduces power dissipation allowing for a temporary power source such as a battery or capacitor to power the system during the course of operation. In at least one exemplary embodiment, a continuous wave energy wave or a pulsed energy wave is provided by transducer  5  to a first surface of waveguide  3 . Transducer  5  generates energy waves  2  that are coupled into waveguide  3 . In a non-limiting example, transducer  5  is a piezo-electric device capable of transmitting and receiving acoustic signals in the ultrasonic frequency range. 
     Transducer  6  is coupled to a second surface of waveguide  3  to receive the propagated pulsed signal and generates a corresponding electrical signal. The electrical signal output by transducer  6  is coupled to phase detector  14 . In general, phase detector  14  compares the timing of a selected point on the waveform of the detected energy wave with respect to the timing of the same point on the waveform of other propagated energy waves. In a first embodiment, phase detector  14  can be a zero-crossing receiver. In a second embodiment, phase detector  14  can be an edge-detect receiver. In the example where sensing assemblage  1  is compressed, the detection of the propagated energy waves  2  occurs earlier (due to the length/distance reduction of waveguide  3 ) than a signal prior to external forces being applied to contacting surfaces. Pulse generator  10  generates a new pulse in response to detection of the propagated energy waves  2  by phase detector  14 . The new pulse is provided to transducer  5  to initiate a new energy wave sequence. Thus, each energy wave sequence is an individual event of energy wave propagation, energy wave detection, and energy wave emission that maintains energy waves  2  propagating in waveguide  3 . 
     The transit time  7  of a propagated energy wave is the time it takes an energy wave to propagate from the first surface of waveguide  3  to the second surface. There is delay associated with each circuit described above. Typically, the total delay of the circuitry is significantly less than the propagation time of an energy wave through waveguide  3 . In addition, under equilibrium conditions variations in circuit delay are minimal. Multiple pulse to pulse timings can be used to generate an average time period when change in external forces occur relatively slowly in relation to the pulsed signal propagation time such as in a physiologic or mechanical system. The digital counter  20  in conjunction with electronic components counts the number of propagated energy waves to determine a corresponding change in the length of the waveguide  3 . These changes in length change in direct proportion to the external force thus enabling the conversion of changes in parameter or parameters of interest into electrical signals. 
     The block diagram  1000  further includes counting and timing circuitry. More specifically, the timing, counting, and clock circuitry comprises a digital counter  20 , a digital timer  22 , a digital clock  24 , and a data register  26 . The digital clock  24  provides a clock signal to digital counter  20  and digital timer  22  during a measurement sequence. The digital counter  20  is coupled to the propagation tuned oscillator  4 . Digital timer  22  is coupled to data register  26 . Digital timer  20 , digital timer,  22 , digital clock  24  and data register  26  capture transit time  7  of energy waves  2  emitted by ultrasound resonator or transducer  5 , propagated through waveguide  3 , and detected by or ultrasound resonator or transducer  5  or  6  depending on the mode of the measurement of the physical parameters of interest applied to surfaces  8 . The operation of the timing and counting circuitry is disclosed in more detail hereinbelow. 
     The measurement data can be analyzed to achieve accurate, repeatable, high precision and high resolution measurements. This method enables the setting of the level of precision or resolution of captured data to optimize trade-offs between measurement resolution versus frequency, including the bandwidth of the sensing and data processing operations, thus enabling a sensing module or device to operate at its optimal operating point without compromising resolution of the measurements. This is achieved by the accumulation of multiple cycles of excitation and transit time instead of averaging transit time of multiple individual excitation and transit cycles. The result is accurate, repeatable, high precision and high resolution measurements of parameters of interest in physical systems. 
     In at least one exemplary embodiment, propagation tuned oscillator  4  in conjunction with one or more sensing assemblages  1  are used to take measurements on a muscular-skeletal system. In a non-limiting example, sensing assemblage  1  is placed between a femoral prosthetic component and tibial prosthetic component to provide measured load information that aids in the installation of an artificial knee joint. Sensing assemblage  1  can also be a permanent component or a muscular-skeletal joint or artificial muscular-skeletal joint to monitor joint function. The measurements can be made in extension and in flexion. In the example, assemblage  1  is used to measure the condyle loading to determine if it falls within a predetermined range and location. Based on the measurement, the surgeon can select the thickness of the insert such that the measured loading and incidence with the final insert in place will fall within the predetermined range. Soft tissue tensioning can be used by a surgeon to further optimize the force or pressure. Similarly, two assemblages  1  can be used to measure both condyles simultaneously or multiplexed. The difference in loading (e.g. balance) between condyles can be measured. Soft tissue tensioning can be used to reduce the force on the condyle having the higher measured loading to reduce the measured pressure difference between condyles. 
     One method of operation holds the number of energy waves propagating through waveguide  3  as a constant integer number. A time period of an energy wave corresponds to energy wave periodicity. A stable time period is one in which the time period changes very little over a number of energy waves. This occurs when conditions that affect sensing assemblage  1  stay consistent or constant. Holding the number of energy waves propagating through waveguide  3  to an integer number is a constraint that forces a change in the time between pulses when the length of waveguide  3  changes. The resulting change in time period of each energy wave corresponds to a change in aggregate energy wave time period that is captured using digital counter  20  as a measurement of changes in external forces or conditions applied to contacting surfaces  8 . 
     A further method of operation according to one embodiment is described hereinbelow for energy waves  2  propagating from transducer  5  and received by transducer  6 . In at least one exemplary embodiment, energy waves  2  is an ultrasonic energy wave. Transducers  5  and  6  are piezo-electric resonator transducers. Although not described, wave propagation can occur in the opposite direction being initiated by transducer  6  and received by transducer  5 . Furthermore, detecting ultrasound resonator transducer  6  can be a separate ultrasound resonator as shown or transducer  5  can be used solely depending on the selected mode of propagation (e.g. reflective sensing). Changes in external forces or conditions applied to contacting surfaces  8  affect the propagation characteristics of waveguide  3  and alter transit time  7 . As mentioned previously, propagation tuned oscillator  4  holds constant an integer number of energy waves  2  propagating through waveguide  3  (e.g. an integer number of pulsed energy wave time periods) thereby controlling the repetition rate. As noted above, once PTO  4  stabilizes, the digital counter  20  digitizes the repetition rate of pulsed energy waves, for example, by way of edge-detection, as will be explained hereinbelow in more detail. 
     In an alternate embodiment, the repetition rate of pulsed energy waves  2  emitted by transducer  5  can be controlled by pulse generator  10 . The operation remains similar where the parameter to be measured corresponds to the measurement of the transit time  7  of pulsed energy waves  2  within waveguide  3 . It should be noted that an individual ultrasonic pulse can comprise one or more energy waves with a damping wave shape. The energy wave shape is determined by the electrical and mechanical parameters of pulse generator  10 , interface material or materials, where required, and ultrasound resonator or transducer  5 . The frequency of the energy waves within individual pulses is determined by the response of the emitting ultrasound resonator  4  to excitation by an electrical pulse  11 . The mode of the propagation of the pulsed energy waves  2  through waveguide  3  is controlled by mode control circuitry  12  (e.g., reflectance or uni-directional). The detecting ultrasound resonator or transducer may either be a separate ultrasound resonator or transducer  6  or the emitting resonator or transducer  5  depending on the selected mode of propagation (reflectance or unidirectional). 
     In general, accurate measurement of physical parameters is achieved at an equilibrium point having the property that an integer number of pulses are propagating through the energy propagating structure at any point in time. Measurement of changes in the “time-of-flight” or transit time of ultrasound energy waves within a waveguide of known length can be achieved by modulating the repetition rate of the ultrasound energy waves as a function of changes in distance or velocity through the medium of propagation, or a combination of changes in distance and velocity, caused by changes in the parameter or parameters of interest. 
     It should be noted that ultrasound energy pulses or waves, the emission of ultrasound pulses or waves by ultrasound resonators or transducers, transmitted through ultrasound waveguides, and detected by ultrasound resonators or transducers are used merely as examples of energy pulses, waves, and propagation structures and media. Other embodiments herein contemplated can utilize other wave forms, such as, light. Furthermore, the velocity of ultrasound waves within a medium may be higher than in air. With the present dimensions of the initial embodiment of a propagation tuned oscillator the waveguide is approximately three wavelengths long at the frequency of operation. 
     Measurement by propagation tuned oscillator  4  and sensing assemblage  1  enables high sensitivity and high signal-to-noise ratio. The time-based measurements are largely insensitive to most sources of error that may influence voltage or current driven sensing methods and devices. The resulting changes in the transit time of operation correspond to frequency, which can be measured rapidly, and with high resolution. This achieves the required measurement accuracy and precision thus capturing changes in the physical parameters of interest and enabling analysis of their dynamic and static behavior. 
     These measurements may be implemented with an integrated wireless sensing module or device having an encapsulating structure that supports sensors and load bearing or contacting surfaces and an electronic assemblage that integrates a power supply, sensing elements, energy transducer or transducers and elastic energy propagating structure or structures, biasing spring or springs or other form of elastic members, an accelerometer, antennas and electronic circuitry that processes measurement data as well as controls all operations of ultrasound generation, propagation, and detection and wireless communications. The electronics assemblage also supports testability and calibration features that assure the quality, accuracy, and reliability of the completed wireless sensing module or device. 
     In general, measurement of the changes in the physical length of individual waveguides can be made in several modes. Each assemblage of one or two ultrasound resonators or transducers combined with a waveguide can be controlled to operate in six different modes. This includes two wave shape modes: continuous wave or pulsed waves, and three propagation modes: reflectance, unidirectional, and bi-directional propagation of the ultrasound wave. In all modes of operation the changes in transit time within the ultrasound waveguides change the operating frequency of the propagation tuned oscillator  4  or oscillators. These changes in the frequency of oscillation of the propagation tuned oscillator or oscillators can be measured rapidly and with high resolution. This achieves the required measurement accuracy and precision thus enabling the capture of changes in the physical parameters of interest and enabling analysis of the dynamic and static behavior of the physical system or body. 
     The level of accuracy and resolution achieved by the integration of energy transducers and an energy propagating structure or structures coupled with the electronic components of the propagation tuned oscillator enables the construction of, but is not limited to, compact ultra low power modules or devices for monitoring or measuring the parameters of interest. The flexibility to construct sensing modules or devices over a wide range of sizes enables sensing modules to be tailored to fit a wide range of applications such that the sensing module or device may be engaged with, or placed, attached, or affixed to, on, or within a body, instrument, appliance, vehicle, equipment, or other physical system and monitor or collect data on physical parameters of interest without disturbing the operation of the body, instrument, appliance, vehicle, equipment, or physical system. 
       FIG. 11  is a cross-sectional view of a layout architecture of the sensing module  200  in accordance with an exemplary embodiment. The blocks are operatively coupled within the encapsulated enclosure of the sensing module  200  and together form an encapsulated force sensor  1100 . It comprises a top steel plate  1104  coupled to a lower printed circuit board (PCB)  1118  by way of spring retainer  1106 , disc spring  1108 , and spring post  1114 . The force sensor  1100  is biased with springs, an elastic support structure or other means to accurately maintain a required distance between the load bearing or contact surfaces such as top cover  1102  and to minimize hysteresis due to material properties of waveguide  1110 . 
     The encapsulating force sensor  1100  supports and protects the specialized mechanical and electronic components from external physical, mechanical, chemical, and electrical, and electromagnetic intrusion that might compromise sensing or communication operations of the module or device. The encapsulating force sensor  1100  also supports internal mechanical and electronic components and minimizes adverse physical, mechanical, electrical, and ultrasonic interactions that might compromise sensing or communication operations of the module or device. Top cover  1102  and unitary main body  1157  form the encapsulating enclosure. Unitary main body  1157  is a metal, plastic, or polymer body having sufficient strength and rigidity to withstand forces, pressures, and loads of the muscular-skeletal system. In particular, the sidewalls or bottom surface do not deform under normal operating conditions. For example, the unitary main body  1157  can be formed of polycarbonate or other biocompatible material. Moreover, unitary main body  1157  can be molded in a manufacturing process that allows detailed features to be repeatably and reliably manufactured. 
     The physical layout architecture of sensor  1100  has the one or more sensing assemblages overlying the electronic circuitry. A force, pressure, or load is applied to a surface of sensor  1100 . The surface of sensor  1100  corresponds to top steel plate  1104 . Steel plate  1104  moves in response to a force, pressure, or load. The steel plate  1104  can support the movement while maintaining a seal with unitary main body  1157  that isolates an interior of the enclosure. In general, a sensing assemblage is coupled between steel plate  1104  and a substrate  1130 . Substrate  1130  is a rigid non-movable substrate that is supported by the sidewalls of unitary main body  1157 . A periphery of substrate  1130  is in contact with and supported by a support feature  1128  formed in the sidewalls of unitary main body  1157 . Substrate  1130  does not flex under loading. The sensing assemblage translates a displacement due to the force, pressure, or load applied to steel plate  1104  to a signal. The signal is processed by electronic circuitry in the enclosure to generate data corresponding to the force, pressure, or load value. As shown, the sensing assemblage comprises upper piezo  1112 , waveguide  1110 , and lower piezo  1124 . Upper piezo  1112  and lower piezo  1124  are ultrasonic piezo-electric transducers. 
     Electronic circuitry to power, control, interface, operate, measure, and send sensor data is interconnected together on a printed circuit board (PCB)  1118 . One or more cups  1120  are formed in unitary main body  1157 . In one embodiment, the components mounted on PCB  1118  reside within cups  1120 . One or more structures  1126  support and fix the position of the PCB  1118 . The components on PCB  1118  are suspended in the cups  1120  and do not have contact with unitary main body  1157  thereby preventing interconnect stress that could result in long-term reliability issues. The PCB  1118  is mechanically isolated from substrate  1130 . Thus, any force, pressure, or loading on substrate  1130  is not applied to PCB  1118 . Flexible interconnect is used to connect from the electronic circuitry on PCB  1118  to upper piezo  1112  and lower piezo  1124 . 
     In one embodiment, more than one sensing assemblage couples to predetermined locations of the steel plate  1104 . Each sensing assemblage can measure a parameter applied to steel plate  1104 . In combination, the sensing assemblages can determine a location or region where the parameter is applied to the surface. For example, the magnitude and position of the loading on the contacting surface of sensing module  200  applied by femur  102  and tibia  108  to sensing module  200  can be measured and displayed as shown in  FIG. 2 . In a non-limiting example, three sensing assemblages can be spaced on a periphery of steel plate  1104 . In the example, each sensing assemblage will measure a force applied to steel plate  1104 . The location of the applied force is closest to the sensing assemblage detecting the highest force magnitude. Conversely, the sensing assemblage detecting the weakest force magnitude is farthest from the applied force. The measured force magnitudes in combination with the predetermined locations where the sensing assemblages couple to steel plate  1104  can be used to determine a location where the parameter is applied. 
     The housing electrically insulates the internal electronic, sensing, and communication components. The encapsulating force sensor  1100  eliminates parasitic paths that might conduct ultrasonic energy and compromise excitation and detection of ultrasound waves within the sensing assemblages during sensing operations. A temporary bi-directional electrical interconnect assures a high level of electrical observation and controllability of the electronic assembly within the encapsulating force sensor  1100 . The temporary interconnect also provides a high level of electrical observation of the sensing subsystem, including the transducers, waveguides, and mechanical spring or elastic assembly. 
     Ultrasound waveguide  1110  is coupled to the top cover  1102 . A force applied to the top cover  1102  compresses waveguide  1110 . Lower piezo  1124  and upper piezo  1112  are piezo-electric transducers respectively coupled to waveguide  1110  at a first and second location. Waveguide  1110  is a compressible propagation medium for ultrasonic energy waves. The transducers emit energy waves and detect propagated energy waves in waveguide  1110 . Electronic circuitry is coupled to lower piezo  1124  and upper piezo  1112  to measure transit time, frequency, or phase of the propagated energy waves. The transit time, frequency, or phase of energy waves propagating between the first and second locations of waveguide  1110  can be precisely measured and therefore the length of the ultrasound waveguide  1110 . The length of waveguide  1110  is calculated by a known function relating material properties of the waveguide  1110  to the parameter being measured. In the example, a force, pressure, or load is calculated from the measured length of waveguide  1110 . 
     The encapsulated force sensor  1100  can accurately and repeatably measure one pound changes in load with changes in length of a waveguide comprising 2.5 microns. The maximum change in the present implementation is specified at less than 5.0 microns. This assures that the size of the sensing module  200  throughout all measurements remains within the required dimension (e.g., distance) of the insert between the load bearing surfaces of the prosthetic components. 
     An exemplary level of control of the compression or displacement of the waveguides  1110  with changes in load, force, pressure, or displacement is achieved by positioning the spring or springs  1108 , elastic support structure, or other means of elastic support, including the waveguides  1110  themselves, between the load bearing contact surfaces to minimize any tendency of the load bearing contact surfaces to cantilever. Cantilevering can compromise the accuracy of the inclination of the load bearing contact surface whenever load, force, pressure, or displacement is applied to any point near a periphery of the load bearing contact surfaces. In one embodiment, springs  1108  are disc springs. The spring  1108  is held in a predetermined location by spring post  1114  and spring retainer  1104 . 
     The walls of the unitary main body  1157  include a small gap to enable the steel plate  1104  to move. The hermetic seal is also flexible to allow the steel plate  1104  of the force sensor  1104  to slide up and down, like a piston, for distances on the order of a hundred microns without compromising integrity of the seal. The hermetic seal completes manufacturing, sterilization, and packaging processes without compromising ability to meet regulatory requirements for hermeticity. The level of hermeticity is sufficient to assure functionality and biocompatibility over the lifetime of the device. Implant devices with total implant time less than 24 hours may have less stringent regulatory requirements for hermeticity. Unbiased electrical circuitry is less susceptible to damage from moisture. The electronics in one embodiment are only powered during actual usage. In another embodiment, the encapsulated force sensor  1100  employs low duty cycles to serve as a measurement-on-demand device to efficiently perform at low total operating time when the electronics are powered on. 
     The encapsulating force sensor  1100  has a compact size permitting it to fit for example within a trial insert, final insert, prosthetic component, tool, equipment, or implant structure to measure the level and incidence of the load on subsequent implanted prosthetic devices. It can be constructed using standard components and manufacturing processes. Manufacturing carriers or fixtures can be designed to emulate the final encapsulating enclosure of the sensing module  200 . Calibration data can be obtained during the manufacturing processing thus enabling capture of accurate calibration data. These calibration parameters can be stored within the memory circuits integrated into the electronics assemblage of the sensing module  200 . Testability and calibration further assures the quality and reliability of the encapsulated enclosure. 
     Examples of a wide range of potential medical applications can include, but are not limited to, implantable devices, modules within implantable devices, intra-operative implants or modules within intra-operative implants or trial inserts, modules within inserted or ingested devices, modules within wearable devices, modules within handheld devices, modules within instruments, appliances, equipment, or accessories of all of these, or disposables within implants, trial inserts, inserted or ingested devices, wearable devices, handheld devices, instruments, appliances, equipment, or accessories to these devices, instruments, appliances, or equipment. 
       FIG. 12  is a simplified cross-sectional view of an embodiment of the load sensing platform  121  in accordance with an exemplary embodiment. The load sensing platform  121  is placed, engaged, attached, or affixed to or within a physical system with a portion of the system contacting the load bearing or contacting surfaces of the load sensing platform  121 . As disclosed in  FIG. 1  the load sensing platform  121  can be used intra-operatively to measure parameters of the muscular-skeletal system during joint replacement surgery. In the example, the load bearing platform  121  is placed in a joint of the muscular-skeletal system to measure force, pressure, or load and the location where the force, pressure, or load is applied. The lower load bearing surface  8  contacts the tibial component  106  of the artificial knee. The upper load bearing surface  8  contacts the femoral component  104  of the artificial knee. Not shown are the muscles, ligaments, and tendons of the muscular-skeletal system that apply a compressive force, pressure, or load on the surfaces  8  of the load sensing platform  121 . The load sensing platform  121  has a form factor that allows integration in tools, equipment, and implants. The load sensing platform  121  is bio-compatible and can be placed in an implant or attached to the muscular-skeletal system to provide long term monitoring capability of natural structures or artificial components. 
     A compact sensing platform is miniaturized to be placed on or within a body, instrument, appliance, vehicle, equipment, or other physical system without disturbing the operation of the body, instrument, appliance, vehicle, equipment, or physical system. This facilitates contacting the sources of load, force, pressure, displacement, density, viscosity, or localized temperature to be measured. The non-limiting example of load sensing platform  121  can include circuitry disclosed in  FIG. 5 . Two or more springs or other means of elastic support  315  support the load bearing or contacting surfaces  8 . One or more assemblages each comprised of one or two ultrasound resonators or transducers are coupled between load bearing surfaces  8 . 
     As shown, a single sensing assemblage  1  is centrally located in load sensing platform  121 . Sensing assemblage  1  is a stack comprising the upper transducer  6 , the lower transducer  5 , and the waveguide  3 . In one embodiment, the waveguide  3  is cylindrical in shape having a first end and a second end. Transducers  5  and  6  respectively overlie the first and second ends of waveguide  3 . An interface material can be used to attach and enhance acoustical coupling between a transducer and waveguide. The stack is positioned in contact with, attached, or coupled to the load bearing or contacting surfaces  8 . Electrical interconnect such as a flex interconnect couples to terminals of transducers  5  and  6 . The flex interconnect (not shown) electrically connects transducers  5  and  6  to electronic circuitry  307  of the sensing module  200 . 
     The upper load bearing surface  8  is a surface of an upper substrate  702 . An interior surface of the upper substrate  702  couples to transducer  6 . Similarly, the lower load bearing surface  8  is a surface of a lower substrate  704 . An interior surface of the lower substrate couples to the transducer  5 . A load, force, or pressure applied across load bearing surfaces  8  can compress or lengthen waveguide  3 . This arrangement facilitates translating changes in the parameter or parameters of interest into changes in the length or compression of the waveguide or waveguides  3  and converting these changes in the length or compression of the waveguide  3  or waveguides into electrical signals by way of transducers  5  or  6  thus enabling sensing assemblage  1  to sense changes in the physical parameters of interest with minimal disturbance to the operation of the external body, instrument, appliance, vehicle, equipment, or physical system. To achieve the required level of miniaturization, the length of the ultrasound waveguides  3  is on the order of 10 millimeters in length. The measurable resolution of compression or displacement of waveguide is on the order of sub-microns. 
     One or more springs  315  or other means of elastic support, support the load bearing or contacting surfaces  8 . The one or more springs control a compression of load sensing platform  121 . For example, waveguide  3  can comprise a polymer material suitable for energy wave propagation. In one embodiment, the polymer material changes dimension when a parameter to be measured is applied to waveguide  3 . A relationship is known between the polymer material and a measured dimension. Changes in dimension are measured and the parameter calculated by way of the known relationship. The polymer material can exhibit mechanical hysteresis whereby the material in-elastically responds to changes in the applied parameter. In the example, the length of waveguide  3  responds to the force, pressure, or load applied across contacting surfaces  8 . Moreover, the polymer material may not rebound in a timely fashion as the force, pressure or load changes. Springs  315  aid in the transition as waveguide  3  responds to different levels of compression. Springs  315  bring the load sensing platform  121  to an accurate and repeatable quiescent state or condition. Springs further prevent the cantilevering of load bearing surfaces  8  that can reduce an accuracy of measurement. Cantilevering becomes more prevalent as forces, pressures, and loads are applied towards the periphery of a contact area of load bearing surfaces  8 . 
     In one embodiment, the springs  315  that support load bearing surfaces  8  are disc springs or a wave springs. Disc springs are capable of maintaining waveguide  3  at a precise length. The compression of the waveguide  3  is very accurate over the measurement range. The compression of the disc springs can be monotonic over the range of applied levels of force, pressure, or load. In one embodiment, the surfaces of the disc springs are polished to assure smooth compression with changes in force applied to contact surfaces  8 . A further benefit of the disk springs is that they eliminate or minimize cantilevering of the load supporting substrate that can compromise the accuracy due to the inclination of load bearing surfaces  8 . In the illustration, two springs  315  are shown that are located on the periphery of load sensing platform  121 . Although not shown, other springs  315  may reside in the load sensing platform  121  at other predetermined locations. Typically, the contact area where the parameter is applied to load bearing surfaces  8  is within an area bounded by springs  315 . 
     In one embodiment, a substrate  706  is resides between upper substrate  702  and lower substrate  704 . Sensing assemblage  1  couples through an opening in substrate  706  to couple to the interior surfaces of substrates  702  and  704  to measure a force, pressure, or load applied across load bearing surfaces  8 . In the example, substrate  702  moves as a force, pressure, or load is applied while substrate  704  remains in a fixed position. Thus, a force, pressure, or load applied to contacting surface  8  changes a distance between substrates  702  and  704  and therefore the length of waveguide  3 . Substrates  704  and  706  are planar to one another separated by a predetermined spacing. Substrates  704  and  706  remain in the fixed relation to one another under loading. 
     Springs  315  are placed between an upper surface of substrate  706  and the interior surface of substrate  702 . As disclosed in the example, springs  315  are disc springs. The disc springs are concave in shape. The disc spring is formed having a centrally located circular opening. The surface of springs  315  proximally located to the circular opening contacts the upper surface of substrate  706 . The surface of springs  315  proximally located to the outer edge of springs  315  contacts the interior surface of substrate  702 . A force applied across the load bearing surface  8  of load sensing platform  121  will compress springs  315  and waveguide  3 . The amount of compression of waveguide  3  over a measurable range can be very small but will provide precision accuracy of the parameter. For example, waveguide  3  may be compressed less than a millimeter for a force measurement ranging from 5 to 100 lbs. In the example, the length of waveguide  3  is precisely measured using acoustic energy wave propagation. The measured length is then converted to the force, pressure, or load. The springs  315  support movement of the waveguide  3  upon a change in force, pressure, or loading. For example, springs  315  repeatably return the load sensing platform  121  to a precise quiescent state upon releasing an applied force. The characteristics of springs  315  are known over the measurement range of load sensing platform  121 . The calculated measured value of the parameter can include compensation due to springs  315 . 
     Spring  315  are in a fixed location in load sensing platform  121 . The disc springs are located on the periphery of the load sensing platform  121 . Spring posts  708  and spring retainers  710  are used to align and fix springs  315  in each predetermined location. Spring post  708  aligns substrate  702  to substrate  706 . Spring post  708  and spring retainer  710  aligns to corresponding openings in substrate  706 . In one embodiment, a cap of post  708  fits into a corresponding cavity of the interior surface of substrate  702 . Spring retainer  710  is a sleeve that overlies post  708 . Post  708  and spring retainer  710  couples through a corresponding opening in substrate  706 . Spring retainer  710  has a lip that overlies and contacts the upper surface of substrate  706 . The spring post  708  and spring retainer  710  couple through the opening in the disc spring. The edge of the opening rests against the edge of the lip of retainer  710  thereby retaining and holding spring  315  in the predetermined location. Spring  315  can move vertically allowing waveguide  3  to change length due to the parameter being applied to contact surfaces  8 . 
     In one embodiment, load sensing platform  121  can locate a position where the parameter is applied on a load bearing surface. Locating the position can be achieved by using more than one sensing assemblages  1 . In one embodiment, three sensing assemblages  1  couple to load bearing or contacting surface  8  at three predetermined locations. The parameter is measured by each sensing assemblages  1 . The magnitudes of each measurement and the differences between measurements of the sensing assemblages  1  are compared. For example, the location of the applied parameter is closer to the sensing assemblage that generates the highest reading. Conversely, the location of the applied parameter will be furthest from the sensing assemblage that generates the lowest reading. The exact location can be determined by comparison of the measured values of each sensing assemblage in conjunction with knowledge of the predetermined locations where each assemblage contacts load bearing or contacting surface  8 . 
       FIG. 14  is an exemplary block diagram schematic of a compact low-power energy source  1400  integrated into an exemplary electronic assembly of the sensing module  200  in accordance with one embodiment. The schematic illustrates one embodiment of the capacitive energy storage  1400  having an induction coupling to an external power source  1402  to transfer energy to a super capacitor or capacitor as an energy storage device that provides operating power for sensing module  200 . The compact low-power energy source  1400  can comprise an induction coil  1404 , a rectifier  1406 , a regulator  1408 , a capacitive energy storage device  1410 , a power management circuit  1412 , and operational circuitry  1414 . The latter circuits can be analog or discrete components, assembled in part or whole with other electronic circuitry, custom designed as an ASIC, or any combination thereof. In one embodiment, the operational circuitry can include circuitry to operate and produce measurement data from sensing assemblages, demodulation circuitry for a wireless receive path, communication circuitry, and secure encoding circuitry. 
     The external energy source  1402  can be coupled to a battery or batteries or an alternating current power supply. For example, external energy source  1402  can be an external hand-held device with its own battery that wirelessly transfers charge from the battery of the hand-held device to the energy source  1400  of the sensing device. The surgeon or technician can hold the hand-held device in close proximity to the sensing device prior to or during orthopedic surgery to provide sufficient charge to operate the device during the procedure. The sensing device as a long-term implant can be charged by the patient at his or her own convenience to initiate a measurement process that provides information on the implant status. In other embodiments, the sensing module  200  being powered by charge from external energy source  1402  can communicate a signal to indicate a recharging operation is necessary, for example, when in the proximity of a charging device. 
     External energy source  1402  can be coupled wirelessly to capacitive energy storage device  1410  through electromagnetic induction coil or coils  1404 , rectifier  1406  and regulator  1408 . The charging operation is controlled by power management circuitry  1412 . During operation of operating circuitry  1414 , power is transferred from capacitive energy storage device  1410  by power management circuitry  1412  that includes, but is not limited to, efficient step-up and step-down voltage converter circuitry that conserves operating power of circuit blocks at the minimum voltage levels that support the required level of performance. Clock frequencies are also optimized for performance, power, and size to assure digital circuit blocks operate at the optimum clock rates that support the required level of performance. Circuit components are partitioned among integrated circuits and discrete components to minimize power consumption without compromising performance. Partitioning functions between digital and analog circuit also enhances design flexibility and facilitates minimizing power consumption without sacrificing functionality or performance. 
     A method of powering and operation of the sensing module is disclosed below. The method can be practiced with more or less than the number of steps shown and is not limited to the order shown. To describe the method, reference will be made to the components of other figures described hereinabove although it is understood that the method can be implemented in any other manner using other suitable components. The sensing module  200  described in  FIG. 5  including capacitive energy storage capability and highly efficient, low power operating performance can be used to illustrate the operating principles of the method. The method is initiated when the external power source  1402  begins transmitting power within range of the induction coil or coils  1404  of the sensing module  200 . In a second step, the induction coils  1404  are coupled to the electromagnetic waves such that the electromagnetic waves are sensed. The induction coil or coils  1404  are energized by the power transmissions from external power source  1402 . In a third step, the coupled electromagnetic waves create an AC power signal in induction coil or coils  1404 . In a fourth step, the rectifier  1406  rectifies the AC power signal to produce a rectified power signal. In one embodiment, a voltage level across induction coil or coils  1404  rises to a level that a rectified signal is generated by full-wave rectifier  1406 . In a fifth step, the rectified power signal is used to charge or provide energy to the capacitive energy storage device  1410 , which holds the charge. In a non-limiting example, the energy storage device  1410  is a super capacitor or capacitor having a small form factor with enough storage capability to power the sensing module  200  for a predetermined period of time. For example, a total knee reconstruction operation takes approximately one to two hours. Capacitive energy storage device  1410  would store sufficient charge to power the sensing module  200  to provide measurements for this length of time. Integrating most of the circuitry on one or two low-power ASICs greatly reduces power consumption of the system making this possible. In a sixth step, the voltage regulator  1408  ensures that the capacitive energy storage device  1410  is charged to, and maintains a voltage level that is greater than the required operating voltage of the sensing module  200 . In a seventh step, the power management circuitry  1412  monitors the level of charge on capacitive energy storage device  1410  to determine if the voltage exceeds a threshold. The threshold can correspond to a shunt threshold established by the regulator  1408 . The operating electronics circuitry  1414  is enabled when it is determined in that an adequate level of charge has been stored to power the sensing module  200  for at least the predetermined time period. 
     In an eighth step, the power management circuitry  1412  disconnects the energy storage device  1410  from the charging circuitry ( 1404 ,  1406 , and  1408 ) when the coupling with external power source  1402  is removed or terminated. Power management circuitry  1412  continues to monitor the level of charge on capacitive energy storage device  1410 . The power management circuitry  1412  powers down the sensing module  200  including the operational circuitry  1414  when the charge or voltage level falls below a predetermined threshold. The power management circuitry  1412  subsequently discharges remaining charge on the energy storage device  1410  to prevent unreliable, intermittent, or erratic operation of the operational circuitry  1414 . 
     Under nominal conditions, a charge time from zero charge to fully charged is approximately 3 minutes. In one embodiment, the maximum charge time is specified to be no greater than 7 minutes. The charging time of a capacitor powered system is a major improvement over the two hours or more required to fully charge a battery from zero charge regardless of battery capacity. The capacitive energy storage device  1410  can include capacitors with solid dielectrics that have longer lifetimes than batteries, can be left uncharged, and will not degrade regardless of length of time at a zero charge. In one arrangement, the wireless charging operation can be performed by electromagnetic induction before removal of any sterile packaging. The capacitive energy storage device  1410  is applicable for powering chronic active implantable devices where data collection is discrete point-of-time measurements rather than continuous, fulltime data collection and storage. 
     The compact low-power energy source can be used as a backup power source for sensing module  200  should the primary power source be terminated. A method performed by the compact low-power energy source as a backup power source is disclosed below. The method can be practiced with more or less than the number of steps shown and is not limited to the order shown. To describe the method, reference will be made to the components of  FIGS. 1 ,  5  and  14 , although it is understood that the method can be implemented in any other manner using other suitable components. The medical sensing device  100  described in  FIG. 1  including capacitive energy storage capability and highly efficient, low power operating performance can be used to illustrate the operating principles of method as a back-up power source. Broadly stated, the method is directed to charging the sensing insert device  100  by way of a wired connection instead of wireless induction charging. 
     In a first step, the induction coil  1404  is electrically decoupled. In a second step, the rectifier  1406  and the regulator  1408  are disabled. At this juncture, the method enters a state where capacitive energy storage device  1410  is decoupled from the wireless charging circuits; that is, the power transmission components inductor  1404 , rectifier  1406 , and regulator  1408  are disabled. As one example, an electrical switching operation disengages the connection upon the power management circuitry  1412  detecting a direct line charge on the capacitive energy storage device  1410 . In another arrangement, the power management circuitry  1412  further checks whether the induction coils are energized at the time of the applied line charge, thereby indicating that the energy is being delivered via a wired connection instead, since no induction activity by an external power source  1402  is detected. 
     In a second step, the wired energy source starts and charges capacitive energy storage device  1410 . The wired energy source maintains capacitive energy storage device  1410  at full charge under normal operating conditions through direct electrical coupling. Power management circuitry  1412  monitors the level of charge on capacitive energy storage device  1410 . If at a third step, power from wired energy source is interrupted, power management circuitry  1412  isolates the capacitive energy storage device  1410  from the wired energy source. As one example, a power interruption occurs when an individual manually disconnects the wired power source from the sensing module  200 . This could also occur in response to an energy spike or power drop in the wired energy source. As another example, a power interruption could occur upon the power management circuitry  1412  detecting the presence of an external power source  1402  attempting to charge the sensing module  200  and thereby competing with the wired energy source. 
     In a fourth step, the power management circuitry  1412  can commence to supply the energy stored on the capacitive energy storage device  1410  to operating circuitry  1414  and associated electronics for normal operation. In a fifth step, power management circuitry  1412  monitors the level of charge on capacitive energy storage device  1410 . In a sixth step, the power management circuitry  1412  will allow the continued supply of energy to the operating circuitry  1414  as long as the voltage on capacitor  1410  exceeds a voltage threshold. In a seventh step, the power management circuitry  1412  powers down the electronic assembly when the charge or voltage level falls below the predetermined charge of voltage threshold. The threshold is chosen to provide sufficient time to power down the operational circuitry  1414  in an orderly fashion. 
     If the wired energy source is restored, power management circuitry  1412  resumes the direct connection of power between the wired energy source and operational circuitry  1414 . Power management circuitry  1412  also resumes the coupling of power between the wired energy source and capacitive energy storage device  1410  and resumes maintaining it at full charge. 
     A method is disclosed for wireless modulation telemetry in accordance with one embodiment. The method can be practiced with more or less than the number of steps shown and is not limited to the order shown. To describe the method, reference will be made to the components of  FIGS. 1 ,  5  and  14 , although it is understood that the method can be implemented in any other manner using other suitable components. 
     In a first step, the external wireless energy source  125  acquires input data. As one example, the user can manually enter the input data via a touchscreen or a user interface menu on the external wireless energy source  125 . In another arrangement, the input data in response to a user directive can be communicatively uploaded to the external wireless energy source  125 , for example, by USB or via a wi-fi connection. The input data can be information such as a serial number, a registration code, biasing parameters (e.g., spring constants, load balancing), updated parameters, version control information, security code information, data log tags, operational control information, or any other data. More specifically, data and instructions to be transmitted to the sensing insert device  100  is input into a data input port  128  of external wireless energy source  125 . 
     As one example, referring back briefly to  FIG. 1 , the receiver station  110  can query a serial number from the sensing insert device  100  for updating medical records and inventory. Sensing insert device  100  includes the sensing module  200 . As another example, the external wireless energy source  125  can download an operation code for adjusting a bias level of one of the springs in the sensing assemblies  303 , or establishing an operating mode (e.g., standby, debug, flash). Following the acquisition of input data, the external wireless energy source  125  can be placed in the proximity of the load insert sensing device  100 . At this point, operation of an external charging device or wireless energy source  1402  is initiated and contact is established with insert sensing device  100 . 
     In a second step, the external wireless energy source  125  proceeds with secure encoding of the input data. As one example, the external wireless energy source  125  by way of a processor embeds cyclic redundancy check (CRC) bits into a data communication packet representing the input data. The CRC is computed and included in the transmission of each data packet. The cyclic redundancy check is based on an algorithm that computes a checksum for a data stream or packets of any length. These checksums can be used to detect interference or accidental alteration of data during transmission. Cyclic redundancy checks are good at detecting errors caused by electrical or electromagnetic noise and therefore enable robust protection against improper processing of corrupted data encoded in energy streams having communication of instructions and data as a secondary function. 
     In a third step, the external wireless energy source  125  modulates the input data onto a TX (transmit) power signal. For instance, the modulation circuit  127  modulates the power signal as a carrier signal and conveys the input data by adjusting at least one of an amplitude, phase, or frequency of the power signal. In the case of wireless energy transfer by resonant induction, the external wireless energy source  125  can modulate the resonant frequency over a small bandwidth to convey the input data in a power efficient manner. In yet another arrangement, timing intervals between energy emissions can be used to convey input data. In a fourth step, the external wireless energy source  125  transmits the TX power signal to the sensing insert device  100 . 
     In a fifth step, the sensing insert device  100  senses the electromagnetic energy waves on the induction coils. In a sixth step, a RX power signal is generated from the received electromagnetic waves. This RX power signal comprises a power signal to provide charge to power to the sensing insert device  100  and a communication signal. As previously discussed, the compact low-power energy source  1400  by way of the induction coils  1404 , rectifier  1406 , and regulator  1408  sense and convert electromagnetic waves to a rectified voltage signal that is then used to charge a super capacitor or capacitor. In one configuration, the external wireless energy source  125  and the compact low-power energy source  1400  employ resonant inductive coupling to provide power efficient transmission over short distances (e.g., less than 20 cm). As an example, the inductors (coils) in conjunction with closely spaced capacitor plates are tuned to a mutual resonant frequency to minimize power loss. The external wireless energy source  125  modulates the power signal around the resonant frequency to transmit power efficiently while simultaneously conveying the communication signal. 
     In a seventh step, the sensing insert device  100  demodulates the communication signal from the RX power signal. The demodulation extracts the information or data from the modulated carrier wave. The demodulation circuit can be in one of the rectifier  1406 , regulator  1408 , power management circuitry  1412 , or operational circuitry  1412 . In an eight step, the sensing insert device  100  securely decodes and validates the information or data. In one embodiment, a cyclic redundancy check checksum is performed to verify the data was not corrupted or received incorrectly. The data is forwarded to control and processing circuitry  307 . In the example, electronic circuitry  307  is on an ASIC integrated circuit with the communication blocks to perform the demodulation, CRC, encoding/decoding, and data validation. As an example, the circuitry can include envelope detectors, phase detectors, oscillators, multipliers, adders, filters, and logic operators. 
     The sensing insert device  100  can then proceed to use the decoded down-link data, for example, to control at least one operation, as shown in a ninth step. As an example, the control operation can place the sensing insert device  100  in a particular operation mode, such as, stand-by or low-power. As another example, the control operation can download a serial number to a local memory on the sensing insert device  100 . The serial number can later be transmitted upon request to a communicatively coupled receiver station  110 . 
     Methods are disclosed hereinbelow for power conservation in accordance with one or more embodiments. The methods can be practiced with more or less than the number of steps shown and is not limited to the order shown. To describe the method, reference will be made to the components of  FIGS. 1 ,  5  and  14 , although it is understood that the method can be implemented in any other manner using other suitable components. In general, a sensing module  200  is coupled to the muscular-skeletal system. The sensing module  200  is used intra-operatively to measure one or more parameters of the muscular-skeletal system to aid in the installation of prosthetic components. In the example disclosed above, the sensing module  200  is placed in a trial insert that dimensionally is substantially equal to the dimensions of a final insert. The trial insert is used in conjunction with other final or permanent prosthetic components to determine fit, function, and allowing modification to fine tune the installation before the final insert is inserted. Similarly, one or more of the final prosthetic components can include sensing module  200 . The disclosed example has the sensing module  200  in the final insert. The sensing modules  200  in the final prosthetic components can measure different parameters than the trial insert. For example, pain, infection, joint kinematics, and bearing surface wear are post-operative parameters of interest. 
     In both the intra-operative and post-operative examples, the sensing module  200  has a form factor that is dimensionally smaller than a prosthetic component. In one embodiment, wired connections for power and communication are not used. In an intra-operative environment, wired connections can get in way of the procedure and limit surgical access. Internal implanted prosthetics such as knee, hip, spine, shoulder, and other joint implants cannot be wired unless terminals protrude through the skin. This is typically not desirable nor an effective long-term solution. The sensing module  200  can incorporate a battery as a temporary power source. As disclosed above, the battery poses the logistical problems of shelf life, installation, charging, and biological hazard. An alternative solution to a battery is using a super or ultra capacitor to power the sensing module  200 . The capacitor has the benefits of form factor, long life, and fast charging time in a solid-state device. 
     The one limitation of a capacitor is the tradeoff of form factor and charge storage. A super or ultra capacitor having a form factor equal to or smaller than a watch battery or other small battery will typically have less energy capability than the battery. In an intra-operative procedure, such as a total knee reconstruction, the sensing module  200  has to deliver precision measurements throughout the surgery. A typical implant operation can last from one hour to several hours. Similarly, the sensing module  200  in a final prosthetic component would need to last a sufficient time to run through one or more measurements of one or more parameters. In both intra-operative and post-operative measurements, the measured parameter data would be sent wirelessly to the surgeon, patient, or healthcare provider. The measured data can be sent in real-time for display or delayed to be reviewed or analyzed at an appropriate time. In general, powering the sensing module  200  with a capacitor would not be a viable solution using off the shelf electronic components or sensors. A capacitor meeting the form factor requirements would not store sufficient charge to sustain device operation for a required operational period of time. 
     Sensing module  200  comprises a compact low-power energy source  1400  that includes the capacitor  1410  that powers the device during a measurement process. The capacitor  1410  is able to sustain operation of sensing module  200  by incorporating power management circuitry  1412  having one or more power conservation modes and an application specific integrated circuit (ASIC). The circuitry of sensing module  200  comprises operational circuitry  1414 , charging circuitry, and power management circuitry  1412 . The operational circuitry  1414  operates one or more sensing assemblages, controls measurement sequences, processes sensing assemblage data, and transmits information. The power management circuitry  1412  operatively couples to circuitry of compact low-power energy source  1400  and operational circuitry  1414  to controllably manage power efficiency of the system thereby enabling the use of the capacitor  1410  to power sensing module  200  for intra-operative and post-operative muscular-skeletal parameter measurements. 
     In one embodiment, the circuitry of sensing module  200  comprises at least one ASIC. The ASIC comprises the majority of the electronic system. The ASIC is architected to operate at low power and provide functionality to perform sensor measurements. In particular, the ASIC includes power management circuitry  1412 , operational circuitry  1414 , portions of compact low-energy source  1400 , and can include wireless communication circuitry. The ASIC comprises complementary metallic oxide semiconductor (CMOS) circuitry that is low voltage and low leakage. The voltage operation is typically 5 volts or less. Voltage operation of analog circuitry can be higher. Digital circuitry can be operated at lower voltages such as 1-3 volts to further reduce power consumption. The ASIC provides a benefit of reduced form factor and low-power operation. 
     The ASIC is further configured in a block architecture. In particular, the operational circuitry  1414  is partitioned in a manner whereby functional blocks can be controlled by the power management circuitry  1412 . A partitioned block, typically performs a function that is independent or not reliant on other blocks being operated and thereby can be turned on or off dependent on need to minimize power consumption. In particular, the power management circuitry  1412  can disable or delay operation of one or more functional blocks to reduce power consumption. In one embodiment, the power management circuitry  1412  makes these decisions based on monitoring the charge or voltage on the capacitor. The amount of charge or voltage can be used to determine when a block is enabled. Partitioning circuit components between structures within the integrated circuit and discrete components enhances design flexibility and minimizes power consumption without compromising performance. Partitioning functions between analog and digital circuitry also enhances design flexibility and facilitate minimizing power consumption without sacrificing functionality or performance. 
     In a first step, a highly efficient step-up or step-down voltage converter is implemented in the compact low-power energy source  1400 . The step-up or step-down voltage converter circuitry enables essentially “lossless” translation of voltage levels. Further conservation of charge is achieved through selection of operating voltages and frequencies that meet device performance specifications. In a second step, reduction in power dissipation is achieved by operating circuitry at minimum frequencies and voltage. The clocking circuitry can be a significant source of power dissipation. Clock drivers can be optimized to efficiently drive a predetermined load. A clock tree or distributed clocking network can be used. The clock tree distribution is optimized in conjunction with the clock drivers to minimize delay and maintain timing at and between distributed nodes providing clock signals. In a third step, the clocked circuitry and the clock frequencies are optimized for power and sized to assure digital circuit blocks are each operated at the optimum clock frequency to achieve required performance with minimum power consumption. 
     Disclosed below are further exemplary embodiments to reduce power consumption of sensing module  200  that utilizes a temporary power source. The power management circuitry  1412  places the sensing module  200  in one or more power conservation modes depending on a current power status as disclosed below. In general, the ASIC can have multiple input and output channels. Each channel can have a dedicated function. For example, input channels can be used to couple to multiple sensors to measure different parameters of the muscular-skeletal system such as temperature, load, or pH. In a fourth step, the input-output channels are operated such that a single output channel or a single input channel is enabled at any point in time. Thus, the inputs or outputs are enabled sequentially or in sequence and are not operated in parallel to improve power efficiency. In a fifth step, a single input circuit and a single output circuit is used. This eliminates parallel input or output operation. The single input and single output circuit are multiplexed to the input-output channels. Typically, measurements of the muscular-skeletal system are not time constrained allowing sequential operation of the input-outputs to reduce peak power consumption. Furthermore, integrating only the single input circuit and the single output driver reduces the surface area of the integrated circuit as well as the amount of active circuitry thereby minimizing parasitic leakage paths. 
     In a sixth step, the architected design of the ASIC includes matching such that the input-output channels matches the input and output requirements of external signals. In the example, specific knowledge of the component characteristics is required to provide the match. In one embodiment, impedance matching produces an efficient energy transfer into and out of the ASIC thereby conserving power. For example, power efficient matching networks are used for coupling to telemetry, sensors, or transducers. The matching is accomplished with appropriate design of the outputs, drivers, and control circuitry within the ASIC that couple to off-board components and devices. In a seventh step, off-board sensors and transducers are also operated at optimum frequencies and drive voltages and currents to achieve the required performance of the wireless module or device at the minimum level of power consumption. Similarly, in an eighth step, operation of all circuit blocks, charging circuitry, and telemetry circuitry are each optimized for minimum total power consumption to achieve required performance levels. This includes, but is not limited to, timing of off and on states. This is coordinated to minimize power drain by optimizing timing and duty cycles of all individual circuit blocks including power drain when powered off plus power consumption to restart each circuit block versus standby power consumption of the separate circuit blocks. 
     The integration of design methods for ultra low power consumption achieves outstanding performance with minimum power drain. This enables highly performing wireless modules or devices powered by a capacitive energy storage device including, but not limited to, ultracapacitors, ultra capacitors, super-caps, super capacitors, or other capacitors. Furthermore, the power management circuitry  1412  can operate in one or more power conservations modes. In a first power conservation mode, the power management circuitry  1412  can turn off, disable, decouple, or disconnect circuitry not being used to conserve power. In a second power conservation mode, the power management circuitry  1412  decouples or turns off the compact low-power energy source  1400  thereby operating on power from capacitor  1410  when power management circuitry  1410  detects that wireless energy source  1402  cannot adequately provide energy or the wireless connection is unstable. In a third power conservation mode, the power management circuitry  1412  reduces a frequency of operation of one or more blocks in the ASIC to reduce operating power. In a fourth power conservation mode, the power management circuitry  1412  disables clock drivers of a clock tree coupled to circuitry not being used. In a fifth power conservation mode, the power management circuitry  1412  can place the operational circuitry in a sleep mode when the circuit is idle for a predetermined time. In a sixth power conservation mode, the power management circuitry  1412  allows parameter measurements to be taken and stored in memory. This can occur when the capacitor  1410  falls below a predetermined threshold. The parameter measurement data is delayed until to an appropriate time to conserve power. In a seventh power conservation mode, only a single input or single output of the ASIC is operated at any time. Finally, an orderly shutdown occurs to preserve parameter measurement data when the power management circuitry  1412  detects that the capacitor falls below a predetermined threshold. In general, the sensing module  200  can be powered by the capacitor  1410  as a result of the power conservation modes and power optimization thereby taking measurements for the duration of a total knee reconstruction. Benefits of the use of capacitors as a power source instead of, or in conjunction with, other power sources or rechargeable technologies include, but are not limited to, enabling a high level of miniaturization, solid state with no chemistries, almost infinite storage lifetime, storage with zero charge, quick charge times, and wireless charging. 
       FIG. 15  is a partial cross-section schematic side view of a sensing platform  1500  including multiple constructed levels comprising electronic substrates with electronic components mounted thereon in accordance with an exemplary embodiment. In the non-limiting example, the sensing platform is used to measure a force, pressure, or load. It is a schematic image of components that fit together to make up an assemblage of transducers, interface materials, electrical interconnect, elastic columns, and mechanical structure using multiple electrical substrates. 
     A sensing assemblage comprises energy propagation medium  1516 , transducer  1512 , and transducer  1514 . Energy propagation medium  1516  is positioned between transducer  1512  and  1514 . In a non-limiting example, energy propagation medium  1516  is shaped as a column. Transducers  1512  and  1514  emit and detect energy waves that propagate through energy propagation medium  1516 . Electronic circuitry coupled to transducers  1512  and  1514  detect changes and measure the transit time, frequency, or phase of the propagated energy waves by controlling the timing and duration. In the example, the transit time, frequency, or phase relates to a force, pressure, or load applied across a top plate  1502  and a bottom plate  1504 . Typically, the bottom plate  1504  provides a resistance  1510  and the load  1508  is applied to the top plate  1502 . In general, plates  1502  and  1504  provide mechanical support and can provide electrical interconnect to a transducer. 
     Flexible interconnect  1506  assures integrity of interconnect while allowing top plate  1502  to move when load  1508  is applied to the surface. The elastic strength of energy propagation medium  1516  contributes to supporting top plate  1502 . The energy propagation medium further maintains a spacing between plates  1502  and  1504 . Under a zero force or quiescent condition the distance between plates  1502  and  1504  are a predetermined distance. The sensing platform  1500  will repeatably return to this predetermined distance under a zero force or quiescent condition. The distance between plates  1502  and  1504  change as a function of the load  1508  applied to the top plate  1502 . Flexible interconnect  1506  provides reliable electrical interconnect to the transducers  1512  and  1514  without restricting the compression or expansion of energy propagation medium  1516  or compromising the integrity of the quantification of the externally applied force, pressure, or load  1508 . 
     In one embodiment, the transducer  1512  contacts an interior surface of top plate  1502 . Similarly, the transducer  1514  contacts an interior surface of bottom plate  1504 . Transducers  1512  and  1514  are positioned at a predetermined location on the interior surfaces of top plate  1502  and bottom plate  1504 . The top plate  1502  and the bottom plate  1504  can comprise an electrically conductive material that can respectively be used as an interconnect to a terminal of transducer  1512  and transducer  1514 . The flexible interconnect  1506  is routed to make electrical contact with transducers  1512  and  1514 . The upper transducer  1512  or piezoelectric component has a conductive interface material or materials where required, solder or conductive adhesive, for electrical connection with flexible interconnect  1506 . The lower transducer  1514  or piezoelectric component has a conductive interface material or materials where required, comprising solder or conductive adhesive  1520  for electrical connection with a second fold or portion of flexible interconnect  1506 . Note, that the flexible interconnect includes a bend, fold, or arc  1522  to provide interconnect to different locations in the sensing assemblage. In the example, the sensing assemblage forms a stack comprising top plate  1502 , transducer  1512 , a first level of flexible interconnect  1506 , energy propagation medium  1516 , a second level of flexible interconnect  1506 , transducer  1514 , and bottom plate  1504 . In this configuration, an energy wave couples through the flexible interconnect  1506 . Moreover, the load  1508  is also applied through the flexible interconnect  1506  as part of the sensing assemblage. Under load  1508 , the energy propagation medium is the only component of the stack that changes length. 
       FIG. 16  is a partial cross-section schematic side view of the sensing platform  1500  including multiple constructed levels comprising electronic substrates with electronic components mounted thereon in accordance with an exemplary embodiment. The sensing platform  1500  has, in addition to the sensing assemblage or assemblages, printed circuit boards  1612  and  1616 . Printed circuit boards  1612  and  1616  are populated with electronic components  1610 . Electronic components  1610  comprise power source circuitry, power management circuitry, telemetry, and operational circuitry for performing parameter measurements. Electronic components  1610  are interconnected by interconnect formed on or within printed circuit boards  1612  and  1616 . Electronic components  1610  are coupled to the sensing assemblage by flexible interconnect  1506 . 
     In the embodiment, the sensing assemblage is between top plate  1502  and bottom plate  1504 . The example sensing assemblage includes an upper transducer  1512  positioned in contact with top plate  1502  and a first side of energy propagation medium  1516 . Similarly, the lower transducer  1514  is positioned in contact with bottom plate  1504  and a second side of energy propagation medium  1516 . This can include conductive interface material or materials where required, solder or conductive adhesive  1602  and  1518  respectively for electrical interconnect with top plate  1502  and electrical contact with flexible interconnect  1506 . The lower transducer  1514  has conductive interface material or materials where required, solder or conductive adhesive  1608  and  1520  respectively for electrical interconnect with bottom plate  1504  and with flexible interconnect  1506 . Solder or conductive adhesive  1608  physically and electrically connect the components. An upper ground disk  1604  provides electrical connection between top plate  1502  and flexible interconnect  1506 . The lower ground disk  1606  provides electrical connection between bottom plate  1504  and flexible interconnect  1506 . An electrical circuit comprising electronic components  1610  and the sensing assemblages is completed by flexible interconnect  1506  that enables electronic components  1610  to operatively control transducers  1512  and  1514  to emit and detect energy waves into and propagating through energy propagation medium  1516 . 
     The electronic components  1610  underlie bottom plate  1504 . In one embodiment, bottom plate  1504  is a rigid substrate that isolates electronic components  1610  from any of the force, pressure, or load applied to the sensing platform. Having the one or more sensing assemblages overlying components  1610  provides a compact profile that allows a sensing module to have a form factor that can be fitted into a prosthetic component for the muscular-skeletal system. At least one printed circuit board is used to connect the electronic components  1610 . In one embodiment, two printed circuit boards are implemented comprising a lower electronic circuit board  1616  and an upper electronic circuit board  1612 . The flexible interconnect  1506  is routed to make electrical contact with the sensing assemblage, upper printed circuit board  1612  and lower printed wiring board  1616 . The flexible interconnect  1506  is placed between and electrically connected to printed circuit boards  1612  and  1616  at predetermined locations. As mentioned previously, the sensing module can include transmit and receive capability. The sensing module can further include an antenna for the wireless communication. In one embodiment, an integrated antenna  1614  is formed on the lower printed circuit board  1616 . As shown, the sensing module includes a stack of five or more layers of interconnect. The flexible interconnect  1506  comprises three levels of interconnect in the stack. 
       FIG. 17  is a partial cross-section schematic side view of a sensing module  1700  including multiple constructed levels comprising electronic substrates with electronic components mounted thereon in accordance with an exemplary embodiment. In particular, the sensing module  1700  includes a housing  1706  and a cap  1702 . The housing  1706  and cap  1702  form an encapsulating enclosure. The encapsulated enclosure houses sensing assemblages, electronic components, electrical interconnect, and mechanical structure using multiple electrical substrates and encapsulating structure as disclosed herein above. In one embodiment, the encapsulating enclosure is hermetically sealed. 
     The housing  1706  comprises sidewalls  1716  and a bottom surface  1714 . Housing  1706  is made of a rigid material such as polycarbonate that can support the force, pressure, or load applied to the sensing module  1700  without flexing and is biocompatible. The interior of sidewalls  1716  include support features or ledges to suspend components at a predetermined height within housing  1706 . Ledges  1708 ,  1710 , and  1712  respectively support and retain bottom plate  1504 , printed circuit board  1612 , and printed circuit board  1616 . The structures can be attached to the ledges by mechanical fastener, adhesive, or other attaching methodology. In one embodiment, the electronic components  1610  on printed circuit board  1616  face the bottom surface  1714  of housing  1706 . The electronic components  1610  mounted on printed circuit board  1612  face the bottom plate  1504 . The electronic components can be selected for each printed circuit board to minimize the combined height thereby reducing the form factor of sensing module  1700 . 
     In one embodiment, an exterior surface of top plate  1502  extends above an upper surface of sidewalls  1716 . The cap  1702  overlies top plate  1502  and the upper surface of sidewalls  1716 . Cap  1702  includes a lip that extends over an exterior surface of sidewalls  1716 . An adhesive  1704  is placed between the sidewall  1716  and the lip of cap  1702  to attach and seal the encapsulating enclosure. Thus, the sensing assemblage and electronic components  1610  are isolated from an external environment. In the example, a force, pressure, or load is applied to the exterior surface of cap  1702 . The force, pressure, or load changes a length of energy propagation medium  1516 . The change in length over the measurement range can be small. For example, energy propagation medium can change less than 5 millimeters to measure a range of 0 to 100 lbs of force. In other embodiments, the change in length can be substantially less than 5 millimeters depending on the material used for energy propagation medium  1516 . The length change corresponds to the movement of cap  1702  and top plate  1502 . Thus, cap  1702  and top plate  1502  are movable structures in relation to housing  1706 . The adhesive  1704  is chosen to allow this movement. For example, a silicone can be used as the adhesive, which is flexible and allows movement. The silicone will also seal the encapsulating enclosure. Alternatively, an o-ring can be used in place of adhesive  1706  as a mechanical solution that allows sealed movement. The transit time, frequency, or phase of propagated energy waves through medium  1516  is captured by electronic components  1610 . The transit time, frequency, or phase can be converted to a length of energy propagation medium  1516 , which is then related to the force, pressure, or load. 
     A method of electronic assembly is disclosed hereinbelow. The method can be practiced with more or less than the number of steps shown and is not limited to the order shown. To describe the method, reference will be made to the components of  FIG. 17 , although it is understood that the method can be implemented in any other manner using other suitable components. In a first step, the conductive interface material or materials are positioned in contact with or affixed to planar or conformal surfaces of each piezoelectric resonator or transducer. In a second step, the sensing assemblage or assemblages, having piezoelectric resonators or transducers  1512  and  1514  and are connected by conductive material or materials such as solder, conductive adhesive, conductive pre-forms, or conductive tape  1518 ,  1520 ,  1602 ,  1608  to flexible interconnect  1506 , top plate  1502 , bottom plate  1504 , electronic components  1610 , upper printed circuit board  1612  and lower printed circuit board  1616  thereby enabling electrical connection and mechanical robustness. Other conductive attaching techniques can be used such as attaching components with double-sided conductive tape or conductive epoxy. Adhesive tape that conducts electricity in the transverse direction only is another example of a conductive adhesive. Magnesium is an example of a potential interface material. 
     In a first variation, the flexible interconnect  1506  is routed to provide additional electrical interconnect to both faces of the transducers thus eliminating the requirement for multiple upper transducers or piezoelectric components to share a common electrical connection. Likewise, the requirement for multiple lower transducers or piezoelectric components sharing a common electrical connection can be eliminated by routing flexible interconnects to provide electrical contact to both faces of these components. This would require additional folds or segments of flexible interconnect. In a second variation, cap  1702  has an external surface that is non-planar or has a conformal surface. The integration of the non-planar or conformal surface or surfaces within the structure of the encapsulating enclosure  304  does not compromise the protective, hermetic, or mechanical support provided by the enclosure  304 . In a third variation, an elastic support between top and bottom plates  1502  and  1504  is provided. The elastic support opposes the force, load, or pressure applied to the sensing module  1700 . The elastic support provides greater flexibility in selecting the maximum force, pressure, or load  1508  that is quantified. In a fourth variation, the transducer  1512  in the sensing assemblage is replaced with a reflective surface or body and all signals propagating within the energy propagation medium is emitted and detected by transducer  1514 . Using the reflective surface also eliminates top ground disk  1604 . In a fifth variation, the sensing assemblage is a MEMS, piezo-resistive, mechanical, or strain gauge device coupled to flexible interconnect  1506 . 
       FIG. 18  is a cross-sectional view of the sensing module  1700  having a small form factor in accordance with an exemplary embodiment. In the example, the external pressure or load can be reliably detected and quantified by the interconnected sensing assemblages and electronic components without direct physical contact. Sensing assemblages  1802  comprises one or more transducers and a compressible propagation medium. Detail of the sensing assemblages  1802  is not visible in this view. Electronic components  1610  are affixed to the upper side of the upper printed circuit board  1612  and the lower side of the printed circuit board  1616  for mechanical support and electrical interconnect. The flexible interconnect  1506  couples the individual transducers  1512  and  1514  to the electrical components  1610  on the printed wiring boards  1612  and  1616  thus enabling complete electrical circuits for electrically stimulating and detecting electrical signals modulated by the energy propagating medium between transducers through the associated column. In particular, the illustrations shows two folds of the flexible interconnect  1506  that extend in an arc to two different levels of flexible interconnect running through the sensing assemblages  1802  that in one embodiment is part of the multi-layer interconnect stack. 
     The encapsulated sensing module or device  1700 , as illustrated, comprises the cap  1702  of housing  1706  that encloses the electronic assemblage comprising sensing assemblages, interconnect, and electronic components. The top plate  1502  transfers flexor with changes in load  1508  of the load-bearing surface of the cap  1702  to the sensing elements of the sensing assemblages  1802 . Mechanical support for electrical and mechanical components within the encapsulated sensing module  1700  is provided by features, ledges, and structures designed into the walls of the housing  1706 . 
       FIG. 19  is a perspective view of the interconnect stack of the sensing module  1700  in accordance with an exemplary embodiment. In the embodiment, three assemblages  1802  couple to predetermined positions of the top plate  1502  (not shown). Multiple sensing assemblages  1802  are used to measure the force, pressure, or load and to identify where on the top plate  1502  (not shown) the parameter was applied. The location where the parameter is applied is determined by the magnitudes measured by each sensing assemblage  1802 , the differential between the measurements, and the location where each sensing assemblage couples to top plate  1502  (not shown). The sensing module  1700  illustrates flexible interconnect supporting electronic components within the sensing assemblage or assemblages  1802 . A single flexible interconnect comprises three levels of interconnection in the interconnect stack. A first level  1806  of the flexible interconnect is shown coupling between the transducers  1512  and corresponding energy propagation medium  1516 . The first level of flexible interconnect  1806  includes a fold, bend, or arc  1812  that connects to a third level  1810  of the flexible interconnect. A second level  1808  of the flexible interconnect is shown coupling between energy propagation medium  1516  and the lower transducer  1514  (not shown). The second level  1808  of the flexible interconnect includes an arc  1804  that connects to the third level  1810  of the flexible interconnect. Note that both the first level  1806  and the second level  1808  includes interconnect that respectively connects to the three transducers  1512  and  1514 . The third level  1810  of the flexible interconnect  1506  is between and connected to printed circuit boards  1612  and  1616 . The printed circuit boards  1612  and  1616  include operational circuitry that couple to the sensing assemblages  1802  to generate parameter measurements from each sensing assemblage  1802 . The upper and lower printed circuit, boards  1612  and  1616 , flexible interconnect  1506 , electronic components  1610 , and bottom plate  1504  illustrate the spatial and mechanical relationships among the electrical substrates. The bottom plate  1504  is between the sensing assemblages  1802  and the electronic components  1610 . It should be noted that in the embodiment, the flexible interconnect is part of the transmission path of the sensing assemblage. Energy waves transmit through the flexible interconnect into the energy propagation medium  1516 . Similarly, propagated energy waves exiting the energy propagation medium  1516  transmit through the flexible interconnect to be detected by a transducer. 
       FIG. 20  is a partial cross-section schematic side view of a sensing platform  2000  including multiple constructed levels comprising electronic substrates with electronic components mounted thereon in accordance with an exemplary embodiment. It is a schematic image of components that fit together to comprise an integrated assemblage having a sensor  2002  attached to flexible electrical interconnect  1506  and supported by top plate  1502  and bottom plate  1504  within an encapsulating enclosure as described hereinabove. The sensor  2002  replaces the sensing assemblage comprising transducer  1512 , energy propagation medium  1516 , and transducer  1514  shown in  FIG. 15 . In the embodiment, a thin film piezo-resistive sensor is used as sensor  2002  to measure the applied force, pressure, or load  1508 . Piezo-resistive pressure sensors typically comprise a layer of pressure sensitive ink sandwiched between two conductive layers. The combination of conductive layers and pressure sensitive ink is encapsulated in a flat package with leads typically extending from a sidewall of the sensor. Sensor  2002  can have a thin form factor that reduces a height of the sensing module. Furthermore, piezo-resistive sensor  2002  is shaped in a manner that allows interconnect stacking. The sensor  2002  has a low level of conductance under a quiescent condition when no force, pressure, or load being applied to the piezo-resistive film. The quiescent condition can also be at a predetermined force, pressure, or load depending on the application. Applying a force, pressure, or load to the piezo-resistive film applies pressure to the ink layer. In the embodiment, the force, pressure, or load applied to top plate  1502  compresses the sensor  2002 . The pressure on the ink increases the conductance as conductive particles are forced in contact or in proximity to each other. The more tightly they are compressed, the lower the resistance of sensor  2002 . Conversely, as pressure is removed, the resistance of sensor  2002  returns to its quiescent state. The sensing platform  2000  can include an elastic structure (not shown) that returns the top plate to a precise position in relation to bottom plate  1504  after the force, pressure, or load is removed. 
     In one embodiment, the piezo-resistive sensing assemblage is a stack that comprises a load disk  2004 , adhesive layer  2006 , sensor  2002 , and an adhesive layer  2008 . The load disk  2004  is a spacer or column that is non-compressible or inelastic. The load disk  2004  can have a major surface that evenly distributes the force, pressure, or load across the major surface sensor  2002 . The major surface of the load disk  2004  has a predetermined area for contacting the sensor  2002 . Adhesive layer  2006  is non-conductive tape, adhesive, or other securing means that attaches load disk  2004  to sensor  2002 . In the embodiment, the load disc  2004  is positioned respectively between top plate  1502  and bottom plate  1504 . Adhesive layer  2008  is non-conductive tape, adhesive, or other securing means that attaches sensor  2002  to bottom plate  1504 . Top plate  1502  transmits the level of force, pressure, or load  1508  externally applied to the top surface (not shown) of the encapsulated enclosure (not shown). The load disk  2004  then couples load  1508  from top plate  1502  to sensor  2002 . The bottom plate  1504  is rigidly supported, through the mechanical structure of the encapsulating enclosure to maintain resistance  1510  to movement thereby enabling accurate quantification of the externally applied force, pressure, or load  1508 . 
     In one embodiment, sensor  2002  has interconnect  2010  and  2012  that extends form the sidewall of the device. Interconnect  2010  and  2012  is connected to flexible interconnect  1506 . Alternatively, sensor  2002  can have electrical contact terminals on either or both major surfaces that receive loading. In this embodiment, flexible interconnect  1506  would be part of the sensing assemblage stack between upper tape  2006 , lower tape  2008 , and sensor  2002  to make one or more connections. Moreover, the flexible interconnect  1506  would receive loading  1508  as part of the sensing assemblage. Current flow through upper interconnect  2010 , sensor  2002 , and lower interconnect  2012  is modulated by changes in force, pressure, or load  1508 . This current flow is carried through traces on the surface of flexible interconnect  1506  to electronic circuitry (not shown) within the sensing module. Flexible interconnect  1506  provides reliable electrical interconnect to the one or more piezo-resistive sensing assemblages without restricting the transmission or compromising the integrity of the force, pressure, or load  1508  applied to the sensing module. In general, thin film piezo-resistive pressure sensors have benefits of simplicity, cost, power, form factor when compared to other sensing technologies. Interfacing with sensor  2002  and interpreting measurement data can reduce both mechanical and circuitry requirements thereby providing further benefit. 
       FIG. 21  is a partial cross-section schematic side view of the sensing platform  2000  including multiple constructed levels comprising electronic substrates with electronic components mounted thereon in accordance with an exemplary embodiment. The sensing platform  2000  has, in addition to the sensing assemblage or assemblages, printed circuit boards  1612  and  1616 . Printed circuit boards  1612  and  1616  are populated with electronic components  1610 . Electronic components  1610  comprise power source circuitry, power management circuitry, telemetry, and operational circuitry for performing parameter measurements. Electronic components  1610  are coupled to the sensing assemblage by flexible interconnect  1506 . In one embodiment, using sensor  2002  in the sensing assemblage requires four layers of electrical interconnect. 
     The electronic components  1610  underlie bottom plate  1504  (not shown). In one embodiment, bottom plate  1504  is a rigid substrate that isolates electronic components  1610  from any of the force, pressure, or load applied to the sensing platform. Having the one or more sensing assemblages overlying components  1610  provides a compact profile that allows a sensing module to have a form factor that can be fitted into a prosthetic component for the muscular-skeletal system. At least one printed circuit board is used to connect the electronic components  1610 . In one embodiment, two printed circuit boards are implemented comprising a lower electronic circuit board  1616  and an upper electronic circuit board  1612 . The flexible interconnect  1506  is routed to make electrical contact with the sensing assemblage, upper printed circuit board  1612  and lower printed wiring board  1616 . The electronic components  1610  detect and digitize changes in levels of the conductance of thin film piezo-resistive sensor  2002 . The measured value of conductance can be converted to a force, pressure, or load value. The flexible interconnect  1506  is placed between and electrically connected to printed circuit boards  1612  and  1616  at predetermined locations. As mentioned previously, the sensing module can include transmit and receive capability. The sensing module can further include an antenna  1614  for the wireless communication. In one embodiment, the antenna  1614  is formed on the lower printed circuit board  1616 . The antenna is a conductive trace on the printed circuit board  1616  formed in loop around the periphery. As shown, the sensing module includes a stack of four layers of interconnect. The flexible interconnect  1506  comprises has connections at two levels of interconnect in the stack. 
       FIG. 22  is a partial cross-section schematic side view of a sensing module  2200  including multiple constructed levels comprising electronic substrates with electronic components mounted thereon in accordance with an exemplary embodiment. In particular, the sensing module  2200  includes a housing  1706  and a cap  1702 . The housing  1706  and cap  1702  form an encapsulating enclosure. The encapsulated enclosure houses sensing assemblages, electronic components, electrical interconnect, and mechanical structure using multiple electrical substrates and encapsulating structure as disclosed herein above. In one embodiment, the encapsulating enclosure is hermetically sealed. 
     The housing  1706  comprises sidewalls  1716  and a bottom surface  1714 . Housing  1706  is made of a rigid material such as polycarbonate that can support the force, pressure, or load applied to the sensing module  1700  without flexing and is biocompatible. The interior of sidewalls  1716  include support features or ledges to suspend components at a predetermined height within housing  1706 . Ledges  1708 ,  1710 , and  1712  respectively support and retain bottom plate  1504 , printed circuit board  1612 , and printed circuit board  1616 . In addition, support structures can be coupled from the bottom surface of housing  1706  for further support or as an option to the ledges. The structures can be attached to the ledges by mechanical fastener, adhesive, or other attaching methodology. In one embodiment, the electronic components  1610  on printed circuit board  1616  face the bottom surface  1714  of housing  1706 . The electronic components  1610  mounted on printed circuit board  1612  face the bottom plate  1504 . The electronic components can be selected for each printed circuit board to minimize the combined height thereby reducing the form factor of sensing module  1700 . 
     In one embodiment, an exterior surface of top plate  1502  extends above an upper surface of sidewalls  1716 . The cap  1702  overlies top plate  1502  and the upper surface of sidewalls  1716 . Cap  1702  includes a lip that extends over an exterior surface of sidewalls  1716 . An adhesive  1704  is placed between the sidewall  1716  and the lip of cap  1702  to attach and seal the encapsulating enclosure. Thus, the sensing assemblage and electronic components  1610  are isolated from an external environment. In the example, a force, pressure, or load is applied to the exterior surface of cap  1702 . The force, pressure, or load is applied through top plate  1502  and load disk  2004  to sensor  2002 . The housing  1706  and bottom plate  1504  provide a resistance against the force, pressure, or load thereby compressing the sensor  2002 . The applied force, pressure, or load to the piezo-resistive film of sensor  2002  results in a corresponding change in resistance of the film. The electronic components  1610  couple to sensor  2002  through flexible interconnect  1506  forming a sensing circuit that detects a change in current or voltage as a result of a resistance change in the piezo-resistive material. The measured current or voltage directly corresponds to the force, pressure, or load. The measurement be stored in memory or transmitted. It should be noted that the applied force, pressure or load causes movement of cap  1702  and top plate  1502 . Thus, both are movable structures in relation to housing  1706 . The adhesive  1704  is chosen to allow this movement. For example, a silicone can be used as the adhesive, which is flexible and allows movement. The silicone will also seal the encapsulating enclosure. An o-ring could also be used in place of adhesive  1706  as a mechanical solution. 
       FIG. 23  is a perspective view  2300  of an exemplary loop antenna  2302  in accordance with one embodiment. As shown, the loop antenna  2302  is integrated along a periphery of the medical device to maximize the antenna trace length and exposure. In such an arrangement, the loop antenna  2302  radiates energy outwards along the circumference of the sensing module thereby enabling low-power operation when used in conjunction with a receiver placed in the vicinity of the sensing module. For instance, in the context of a load sensing insert device  100  used in knee implant surgery, the outer periphery is closest to the outside of the knee where a receiver device can be placed on the skin to scan the sensing module  200  for communication data. In this illustration, the loop antenna  2302  forms one or more loops along the outermost periphery of the encapsulated sensing module  200  as permitted by the encapsulated printed circuit board or electronic packaging substrate. A port  2304  includes two terminals that serve to couple the loop antenna  2302  to electronic components of the sensing module  200 , such as the transceiver  320 . The port  2304  can also couple external to the sensing module  200 . The port  2304  couples to communication circuitry within the sensing module  200  and an antenna. In one embodiment, a matching network can be placed between transceiver  320  and antenna  2302  to improve efficiency. In an alternative embodiment, the loop antenna  2302  is formed on a flexible interconnect instead of a printed circuit board within the sensing module  200 . The flexible interconnect couples the antenna  2302  to the communication circuitry and can include a bend that positions the loop antenna  2302  appropriately within the sensing module for transmission of data. 
     In another embodiment, the loop antenna  2302  is electrically coupled to the insert dock  202 . The insert dock  202  is larger than sensing module  200  and has a larger peripheral area. A longer conducting antenna loop is formed in, on, or around the insert dock  202  for radio frequency communication. As an example, the insert dock  202  includes electrical wiring to serve as the loop antenna  2302 . A hermetically sealed communications port resides on sensing module  200 . As mentioned, the port  2304  couples to the communication circuitry and can be external to the sensing module  200 . In one embodiment, port  2304  couples to the matching network. The external communication port on sensing module  200  connects to a corresponding port on the insert dock when inserted. The port or terminals on insert dock  202  connect to the antenna loop in or on the insert dock  202 . In yet another arrangement, the insert dock  202  can comprise metal for being a conductor of radio communications. 
       FIG. 24  is a perspective view  2400  of an integrated loop antenna  2402  according to another embodiment. As illustrated, the integrated loop antenna  2402  is integrated into a substrate of a printed circuit board  2406  of the sensing insert device  100 . Other embodiments are not limited to the illustrated loop, or similarly shaped or functioning integrated loop antennas. As shown, the integrated loop antenna  2402  comprises circuit traces  2404  on a top (or bottom) layer of the substrate of the circuit board  2406 . The traces  2404  act as a portion of the radiating and receiving body of the integrated loop antenna  2402 . The circuit board  2406  can comprise multiple interconnect layers that can be formed as part of the radiating and receiving body, counterpoise, reflectors, or other structural components of the antenna  2402 . The circuit traces  2404  can be etched to navigate around other electrical components and even the edge of the circuit board in certain embodiments. 
     Printed circuit technology supports the creation of many shapes of conductors and conducting surfaces on each layer of a multi-layer circuit board or flexible substrate. These conductors and conducting surfaces may be arranged and interconnected to function as radiating or receiving, reflection, and other surfaces of an integrated antenna. The conductors and conducting surfaces on each individual layer of the substrate may be interconnected in a variety of configurations. Conductors and conducting surfaces on each layer of the substrate may also be connected with conductors and conducting surfaces on other layers in a variety of configurations. This provides flexibility to design and integrate many forms of antennas with different radiation patterns, polarizations, frequency ranges, levels of Q, and impedance characteristics. 
     The circuit board  2406  comprises a matching network A, a radio frequency output stage B, and optional receiver circuit C. These block diagram components are functionally related to the transceiver  320  and electronic circuitry  307  of  FIG. 5 . The block models can comprise analog components, digital components, discrete components, integrated circuit components or any combination thereof. As shown, the circuitry is mounted on circuit board  2406 . The matching network A provides impedance matching to an external receiver communications network to provide optimal power efficiency. The radio frequency output stage B drives the matching network A. The radio frequency output stage B amplifies and transmits communication signals to an external receiver. In the example, the communication signal will carry information that includes parameter measurement data such as load and balance measurements. The receiver circuit C is an optional component that can be integrated by way of switching (e.g., a Transmit-Receive (TR) switch) to receive data communications from an external transmitter, for example, to download a serial number. 
     The integration of the antenna  2402  into a rigid or flexible substrate for electronic circuits enables highly compact Radio Frequency (RF) modules, devices, instruments, or equipment with adequate radiating efficiency to operate at low power levels in many short-range applications. Integrated antennas have adequate receiving sensitivity for many of these applications as well. In one embodiment, the transmit power in conjunction with the loop antenna  2402  can be designed to limit the transmission distance. For example, it can restrict communication transmission to a distance corresponding to an operating room, doctor&#39;s office, or patient home thereby preventing or deterring others from receiving the measurement data. In one embodiment, the sensing module  200  is in an implant that would underlie tissue and portions of the muscular-skeletal system. In the embodiment, a portable receiver would be placed near the implant to receive or transmit information to the sensing module. These wireless modules, devices, instruments, or equipment may be constructed using high volume, low cost, standard manufacturing processes thus producing high quality, high reliability, deeply miniaturized radio frequency transmitter or receiver modules, devices, instruments, or equipment. 
     Integration of the antenna  2402  within the electronic assembly enables the construction of compact wireless equipment. In addition to a wide range of short-range handheld, wearable, or other portable communication equipment, many applications may also include data measurement, collection, and communication modules, devices, or equipment for a wide range of applications. Additional potential applications may include, but are not limited to, a wide range of medical applications. Potential medical applications may include, but are not limited to, intra-operative medical devices, trial inserts, and implants, other short-term medical devices, including devices that are inserted or ingested, other implanted medical devices, wearable medical devices, handheld devices, disposable medical devices or modules, medical instruments, medical equipment, accessories for medical instruments and equipment, and disposables associated with medical instruments, equipment, accessories. 
       FIG. 25  Illustrates by way of example, a plot  2500  of normalized radiated field strength  2502  versus frequency  2504  performance of an example loop antenna integrated into a rigid or flexible substrate of the electronic circuit board. The plot  2500  illustrates radiation efficiency of the antenna and matching network from a circuit analysis. By way of electronic circuitry  307 , the loop antenna can be configured to produce a frequency of maximum power output  2506 . The electronic circuitry can further shape the peak (or radiation pattern) via a tuning mechanism to narrow (broaden) the peak and the relative Q level of the antenna. As one example, the electronic circuitry can emit a beacon signal over a broad frequency span, and upon receiving a ping for a particular communication channel, self-configure to narrow the peak to receive further communications under optimal power communication settings. 
       FIG. 26  Illustrates a radiation pattern of the loop antenna integrated into a flexible substrate of an electronic circuit in accordance with an exemplary embodiment. The axes of the null points are readily visible and indicate that direction performance of reception and transmission can be well suited to applications where directional communications minimize the potential for inference. For instance, in the current antenna layout pattern, wherein the loop antenna is along an outer periphery, a radiation pattern is generated in a shape that propagates away from the implant site and in a direction, which facilitates acceptable signal to noise ratio (SNR). As shown, the null radiation lobes  2604  of the antenna pattern  2602  can be seen at positions where it may be less practical to place the receiver (e.g., along the femur or tibial axis), and that higher radiation lobes (or patterns)  2606  of the antenna pattern  2602  are along the outside periphery of the implant and are closest to the patient skin surface where a receiver can be placed. In other embodiments, the loop antenna can be physically configured, and in conjunction with control circuitry, to indicate a strong directional pattern of preferred reception and transmission thus making one particular instance of an integrated loop antenna well suited to applications that require omni-directional communications. 
       FIG. 27  illustrates a low power consumption integrated transducer driver circuit  2700  in accordance with an exemplary embodiment. In a first embodiment, driver circuit  2700  efficiently drives a transducer to generate time and frequency specific energy waves and pulses. It includes digital logic to generate drive signals according to the transducer characteristics and operational modes to achieve highly accurate control, timing, and duration of the generated energy waves and pulses. In one arrangement, the output driver is coupled to an ultrasonic sensing assembly to efficiently generate continuous ultrasonic waves or ultrasonic pulses that propagate through a propagation medium. The driver circuit includes a level shifter  2712  to raise or lower voltage levels of output pulses to voltage levels required to efficiently drive an energy emitting resonator or transducer given the characteristics of the resonator or transducer, the frequency and duration of the output waves, and the shape of the output pulse. It includes an impedance matching network  2714  to translate the digital output pulse into a required wave shape for efficiently and compactly driving the transducer. This configuration provides the benefit for battery or temporarily powered sensing systems to drive the energy emitting resonators or transducers with much less power consumption than a Digital to Analog Converter (DAC) based design. 
     In a second embodiment, the driver circuit  2700  is incorporated within a propagation tuned oscillator (PTO) to maintain positive closed-loop feedback. The PTO can operate in continuous wave mode, pulse-loop mode, pulse-echo mode, or controlled combination thereof. The driver circuit  2700  is electrically integrated with the PTO by multiplexing input and output circuitry, including off-board components of an impedance matching network, to achieve ultra low-power and small compact size. In this arrangement, off-board energy emitting resonators or transducers are operated at optimum frequencies and drive voltages and currents to achieve optimal performance at a minimum level of power consumption. The drive circuit  2700  can singly drive multiple energy emitting resonators or transducers to achieve this level of performance; that is, only one driver circuit can be shared. Appropriate duty cycles and multiplexing timing for optimum frequencies of the energy emitting resonators or transducers are selected to conserve both power and space without compromising performance. This enables, but is not limited to, the design and construction of compact measurement modules or devices with thickness on the order of a few millimeters. 
     In one embodiment, low power consumption transducer driver circuit  2700  comprises control logic  2708 , a digital driver  2706 , level shifter  2712 , an amplifier  2716 , and matching network  2714 . The driver circuit  2700  can be implemented in discrete analog components, digital components, an application integrated circuit, or a combination thereof. In a low power application, transducer driver circuit  2700  is integrated with other circuitry of the propagation tuned oscillator. Briefly, the transducer driver circuit  2700  accurately controls emissions of energy waves or pulses, and parameters thereof, including, but not limited to, transit time, phase, or frequency of the energy waves or pulses. A brief description of the method of operation is as follows. 
     An input  2702  receives a signal to emit an energy wave. Input  2702  couples to control logic  2708 . Control logic  2708  controls the timing and frequency of stimulation of an energy transducer  2710 . A digital pulse  2704  from digital control logic  2708  is provided to an input of driver  2706 . In an energy pulse mode, digital control logic  2708  also controls the duration of the stimulation. One or more pulses from an output  2718  of driver  2706  are coupled to level shifting circuitry  2712 . Level shifting circuitry  2712  adjusts the output voltage of driver  2706  to efficiently drive energy transducer  2710 . One or more level shifted pulses are provided at an output  2720  of level shifter  2712  to amplifier  2716 . Amplifier  2716  amplifies the signal at output  2720 , which is provided, to an input of matching network  2714 . Matching network  2714  matches the electrical characteristics of the energy transducer  2710 . The output signal  2722  from the matching network  2714  enables energy transducer  2710  to emit an energy wave. Matching network  2714  converts the output pulse from amplifier  2716  to the required wave shape, frequency and phase. Transducer  2710  emits energy waves  2724  into the medium upon excitation by the signal output from matching network  2714 . 
     As discussed above, the electronic components are operatively coupled as blocks of integrated circuits. As will be shown ahead, this integrated arrangement performs its specific functions efficiently with a minimum number of components. A portion of the efficiency is achieved because the circuit components are partitioned between structures within an integrated circuit and discrete components, as well as innovative partitioning of analog and digital functions, to achieve the required performance with a minimum number of components and minimum power consumption. 
     Briefly, an input of digital driver  2706  is driven by digital control logic  2708 , which ultimately controls the timing and frequency of the resulting output signal  2722 . As will be shown ahead, the output signal  2722  drives an energy transducer  2710  to output an energy wave or energy pulse. The drive circuit  2700  is optimally configured to generate the output signal  2722  according to the transducer characteristics (e.g., frequency, stiffness, Q, ringing, inductance, ringing, decay, feedback) and in certain cases the operating mode (e.g., continuous, pulse-loop, and pulse echo). For example, in pulse-loop mode, digital control logic  2708  also controls the duration of the transducer  2710  stimulation. Level shifter  2712  adjusts the output voltage of driver output  2706  to efficiently drive energy transducer  2710 . More specifically, the level shifter  2712  raises or lowers voltage levels of output pulses to the voltages required to efficiently drive the energy emitting resonator or transducer  2710  given the characteristics of the resonator or transducer  2710 , the frequency and duration of the output waves, and the shape of the output pulse. Matching network  2714  matches the electrical characteristics of the energy transducer  2710  and converts the output pulse  2722  to the required wave shape, frequency and phase. The generated digital output waveform  2722  or pulse may have a moderately sharp leading edge. 
     With regard to the integrated transducer driver  2700 , efficient use of power and conservation of charge is required for ultra low power operation. Energy emitting resonators or transducers  2710  can be stimulated with a sine wave or other form of continuous wave to efficiently emit energy waves of the required frequency, phase, and duration. Partitioning circuit components between structures within the integrated circuit and discrete components enhances design flexibility and minimize power consumption without compromising performance. Therefore, the driver circuit  2700  and matched network  2714  together efficiently convert the input pulse  2704  to an energy wave  2724  of the required frequency, phase, and duration, which is specific to operation of transducer  2710 . 
     The output of the driver amplifier  2716  is coupled with the impedance matching network  2714 , such as, but not limited to, a pi network. This pi network can include a discrete inductor or inductors and a discrete capacitor or capacitors to translate the digital output pulse into the required wave shape efficiently and compactly. In one arrangement, the phase and time delay through the pi network are constant. The pi network may also include resistance as well as the discrete inductance and capacitance components. The resistance element is included in the analysis and comprises parasitic resistances within the integrated components and interconnects of the circuit. They are included in the analysis and design of the pi network to assure matching the electrical drive requirements of the energy emitting device. 
     The impedance matching network  2714  generates a waveform  2722  that is optimized for emitting resonator or transducer  2710 . The network  2714  drives the energy emitting resonators or transducers  2710  efficiently thereby reducing power consumption. In particular, the power consumption is substantially less than using an equivalent Digital to Analog Converter (DAC) based design. The integration of miniature, surface mountable, inductors and capacitors enables highly compact driver circuit and minimizes the total number of electronic components. In a hybrid approach, off-chip and return to on-chip, may have size penalty but can be integrated to save power and reduce design complexity. 
       FIG. 28  illustrates a block diagram of an edge-detect receiver circuit  2800  in accordance with an exemplary embodiment. In a first embodiment, edge-detect receiver  2800  is provided to detect wave fronts of energy waves. This enables capturing of parameters including, but not limited to, transit time, phase, or frequency of the energy waves. Circuitry of the integrated edge-detect receiver  2800  provides rapid on-set detection and quickly responds to the arrival of an energy wave. It reliably triggers thereafter a digital output pulse at a same point on the initial wave front of each captured energy wave or pulsed energy wave. The digital pulse can be optimally configured to output with minimal and constant delay. The edge-detect receiver  2800  can isolate and precisely detect the specified point on the initial energy wave or the wave front in the presence of interference and distortion signals thereby overcoming problems commonly associated with detecting one of multiply generated complex signals in energy propagating mediums. The edge-detect receiver  2800  performs these functions accurately over a wide range of amplitudes including very low level energy pulses. 
     In a second embodiment, the edge-detect receiver  2800  is incorporated within a propagation tuned oscillator (PTO) to maintain positive closed-loop feedback when operating in a continuous wave, pulse or pulse-echo mode. The edge-detect receiver  2800  can be integrated with other circuitry of the PTO by multiplexing input and output circuitry to achieve ultra low-power and small compact size. Integration of the circuitry of the PTO with the edge-detect receiver provides the benefit of increasing sensitivity to low-level signals. 
     The block diagram illustrates one embodiment of a low power edge-detect receiver circuit  2800  with superior performance at low signal levels. The edge-detect receiver  2800  comprises a preamplifier  2812 , a differentiator  2814 , a digital pulse circuit  2816  and a deblank circuit  2818 . The edge-detect receiver circuit  2800  can be implemented in discrete analog components, digital components or combination thereof. In one embodiment, edge-detect receiver  2800  is integrated into an ASIC as part of a sensor system described hereinbelow. The edge-detect receiver circuit  2800  practices measurement methods that detect energy pulses or pulsed energy waves at specified locations and under specified conditions to enable capturing parameters including, but not limited to, transit time, phase, frequency, or amplitude of energy pulses. A brief description of the method of operation is as follows. In a non-limiting example, a pre-amplifier triggers a comparator circuit responsive to small changes in the slope of an input signal. The comparator and other edge-detect circuitry responds rapidly with minimum delay. Detection of small changes in the input signal assures rapid detection of the arrival of a pulse of energy waves. The minimum phase design reduces extraneous delay thereby introducing less variation into the measurement of the transit time, phase, frequency, or amplitude of the incoming energy pulses. 
     An input  2820  of edge-detect receiver  2800  is coupled to pre-amplifier  2812 . As an example, the incoming wave  2810  to the edge-detect receiver circuit  2800  can be received from an electrical connection, antenna, or transducer. The incoming wave  2810  is amplified by pre-amplifier  2812 , which assures adequate sensitivity to small signals. Differentiator circuitry  2814  monitors the output of pre-amplifier  2812  and triggers digital pulse circuitry  2816  whenever a signal change corresponding to an energy wave is detected. For example, a signal change that identifies the energy wave is the initial wave front or the leading edge of the energy wave. In one arrangement, differentiator  2814  detects current flow, and more specifically changes in the slope of the energy wave  2810  by detecting small changes in current flow instead of measuring changes in voltage level to achieve rapid detection of slope. Alternatively, differentiator  2814  can be implemented to trigger on changes in voltage. Together, preamplifier  2812  and differentiator  2814  monitor the quiescent input currents for the arrival of wave front of energy wave(s)  2810 . Preamplifier  2812  and differentiator  2814  detect the arrival of low level energy waves as well as large magnitude energy waves. This detection methodology achieves superior performance for very low level signals. Differentiator circuitry  2814  triggers digital pulse circuitry  2816  whenever current flow driven by the initial signal ramp of the incoming wave  2810  is detected. The digital pulse is coupled to deblank circuit  2818  that desensitizes pre-amplifier  2812 . For example, the desensitization of pre-amplifier  2812  can comprise a reduction in gain, decoupling of input  2820  from energy wave  2810 , or changing the frequency response. The deblank circuit  2818  also disregards voltage or current levels for a specified or predetermined duration of time to effectively skip over the interference sections or distorted portions of the energy wave  2810 . In general, energy wave  2810  can comprise more than one change in slope and is typically a damped wave form if the energy wave is pulsed. Additional signals or waves of the pulsed energy wave on the input  2820  of pre-amplifier  2812  are not processed during the preset blanking period. In this example, the digital output pulse  2828  can then be coupled to signal processing circuitry as explained hereinbelow. In one embodiment, the electronic components are operatively coupled as blocks within an integrated circuit. As will be shown ahead, this integration arrangement performs its specific functions efficiently with a minimum number of components. This is because the circuit components are partitioned between structures within an integrated circuit and discrete components, as well as innovative partitioning of analog and digital functions, to achieve the required performance with a minimum number of components and minimum power consumption. 
       FIG. 29  is a block diagram of a zero-crossing receiver  2900  in accordance with one embodiment. In a first embodiment, the zero-crossing receiver  2900  is provided to detect transition states of energy waves, such as the transition of each energy wave through a mid-point of a symmetrical or cyclical waveform. This enables capturing of parameters including, but not limited to, transit time, phase, or frequency of the energy waves. The receiver rapidly responds to a signal transition and outputs a digital pulse that is consistent with the energy wave transition characteristics and with minimal delay. The zero-crossing receiver  2900  further discriminates between noise and the energy waves of interest, including very low level waves by way of adjustable levels of noise reduction. A noise reduction section  2918  comprises a filtering stage and an offset adjustment stage to perform noise suppression accurately over a wide range of amplitudes including low level waves. 
     In a second embodiment, a zero-crossing receiver  2900  is provided to convert an incoming symmetrical, cyclical, or sine wave to a square or rectangular digital pulse sequence with superior performance for very low level input signals. The digital pulse sequence represents pulse timing intervals that are consistent with the energy wave transition times. The zero-crossing receiver  2900  is coupled with a sensing assembly to generate the digital pulse sequence responsive to evaluating transitions of the incoming sine wave. This digital pulse sequence conveys timing information related to parameters of interest, such as applied forces, associated with the physical changes in the sensing assembly. 
     In a third embodiment, the integrated zero-crossing receiver is incorporated within a propagation tuned oscillator (PTO) to maintain positive closed-loop feedback when operating in a continuous wave mode, pulse mode, or pulse-echo mode. The integrated edge zero-crossing receiver is electrically integrated with the PTO by multiplexing input and output circuitry to achieve ultra low-power and small compact size. Electrical components of the PTO are integrated with components of the zero-crossing receiver to assure adequate sensitivity to low-level signals. 
     In one embodiment, low power zero-crossing receiver  2900  can be integrated with other circuitry of the propagation tuned oscillator to further improve performance at low signal levels. The zero-crossing receiver  2900  comprises a preamplifier  2906 , a filter  2908 , an offset adjustment circuitry  2910 , a comparator  2912 , and a digital pulse circuit  2914 . The filter  2908  and offset adjustment circuitry  2910  constitute a noise reduction section  2918  as will be explained ahead. The zero-crossing receiver  2900  can be implemented in discrete analog components, digital components or combination thereof. The integrated zero-crossing receiver  2900  practices measurement methods that detect the midpoint of energy waves at specified locations, and under specified conditions, to enable capturing parameters including, but not limited to, transit time, phase, or frequency of energy waves. A brief description of the method of operation is as follows. 
     An incoming energy wave  2902  is coupled from an electrical connection, antenna, or transducer to an input  2904  of zero-crossing receiver  2900 . Input  2904  of zero-crossing receiver  2900  is coupled to pre-amplifier  2906  to amplify the incoming energy wave  2902 . The amplified signal is filtered by filter  2908 . Filter  2908  is coupled to an output of pre-amplifier  2906  and an input of offset adjustment circuitry  2910 . In one configuration, filter  2908  is a low-pass filter to remove high frequency components above the incoming energy wave  2902  bandwidth. In another arrangement, the filter is a band-pass filter with a pass-band corresponding to the bandwidth of the incoming energy wave  2902 . It is not however limited to either arrangement. The offset of the filtered amplified wave is adjusted by offset adjustment circuitry  2910 . An input of comparator  2912  is coupled to an output of offset adjustment circuitry  2910 . Comparator  2912  monitors the amplified waveforms and triggers digital pulse circuitry  2914  whenever the preset trigger level is detected. Digital pulse circuit  2914  has an input coupled to the output of comparator  2912  and an output for providing digital pulse  2916 . The digital pulse  2916  can be further coupled to signal processing circuitry, as will be explained ahead. 
     In a preferred embodiment, the electronic components are operatively coupled together as blocks of integrated circuits. As will be shown ahead, this integrated arrangement performs its specific functions efficiently with a minimum number of components. This is because the circuit components are partitioned between structures within an integrated circuit and discrete components, as well as innovative partitioning of analog and digital functions, to achieve the required performance with a minimum number of components and minimum power consumption. 
       FIG. 30  is a sensor interface diagram incorporating the zero-crossing receiver  2900  in a continuous wave multiplexing arrangement for maintaining positive closed-loop feedback in accordance with one embodiment. The positive closed-loop feedback is illustrated by the bold line path. Initially, multiplexer (mux)  3002  receives as input a clock signal  3004 , which is passed to the transducer driver  2700  to produce the drive line signal  3008 . Analog multiplexer (mux)  3010  receives drive line signal  3008 , which is passed to the transmitter transducer  3012  to generate energy waves  3014 . Transducer  3012  is located at a first location of an energy propagating medium. The emitted energy waves  3014  propagate through the energy propagating medium. Receiver transducer  3016  is located at a second location of the energy propagating medium. Receiver transducer  3016  captures the energy waves  3014 , which are fed to analog mux  3020  and passed to the zero-crossing receiver  2900 . The captured energy waves by transducer  3016  are indicated by electrical waves  3018  provided to mux  3020 . Zero-crossing receiver  2900  outputs a pulse corresponding to each zero crossing detected from captured electrical waves  3018 . Alternatively, edge-detect receiver  2800  can be used to detect propagated energy waves. The zero crossings are counted and used to determine changes in the phase and frequency of the energy waves propagating through the energy propagating medium. In a non-limiting example, a parameter such as applied force is measured by relating the measured phase and frequency to a known relationship between the parameter (e.g. force) and the material properties of the energy propagating medium. In general, pulse sequence  3022  corresponds to the detected signal frequency. The zero-crossing receiver  2900  is in a feedback path of the propagation tuned oscillator. The pulse sequence  3022  is coupled through mux  3002  in a positive closed-loop feedback path. The pulse sequence  3022  disables the clock signal  3004  such that the path providing pulse sequence  3022  is coupled to driver  2700  to continue emission of energy waves into the energy propagating medium and the path of clock signal  3004  to driver  2700  is disabled. The pulse sequence can comprise one or more pulses. Thus, closing the loop continues a process of energy wave emission, energy wave propagation, and detection of the energy wave in the energy propagation medium with the detection generating a new signal to initiate a next emission. 
       FIG. 31  is an exemplary block diagram of a propagation tuned oscillator (PTO) incorporating the zero-crossing receiver  3140  for operation in continuous wave mode. In particular, it illustrates closed loop measurement of the transit time of ultrasound waves within a waveguide by the operation of the propagation tuned oscillator as disclosed hereinabove. Alternatively, an edge-detect receiver can be used for energy wave detection. This example is for operation in continuous wave mode. The system can also be operated in pulse mode and a pulse-echo mode. Pulse mode and pulsed echo-mode use a pulsed energy wave. Pulse-echo mode uses reflection to direct an energy wave within the energy propagation medium. Briefly, the digital logic circuit  3146  digitizes the frequency of operation of the propagation tuned oscillator. 
     In continuous wave mode of operation a sensor comprising transducer  3104 , propagating structure  3102 , and transducer  3106  is used to measure the parameter. In general, the parameter to be measured affects the properties of the propagating medium. For example, an external force or condition  3112  is applied to propagating structure  3102  that changes the length of the waveguide in a path of a propagating energy wave. A change in length corresponds to a change in transit time  3108  of the propagating wave. Similarly, the length of propagating structure  3102  corresponds to the applied force  3112 . A length reduction corresponds to a higher force being applied to the propagating structure  3102 . Conversely, a length increase corresponds to a lowering of the applied force  3112  to the propagating structure  3102 . The length of propagating structure  3102  is measured and is converted to force by way of a known length to force relationship. 
     Transducer  3104  is an emitting device in continuous wave mode. The sensor for measuring a parameter comprises transducer  3104  coupled to propagating structure  3102  at a first location. A transducer  3106  is coupled to propagating structure  3102  at a second location. Transducer  3106  is a receiving transducer for capturing propagating energy waves. In one embodiment, the captured propagated energy waves are electrical sine waves  3134  that are output by transducer  3106 . 
     A measurement sequence is initiated when control circuitry  3118  closes switch  3120  coupling oscillator output  3124  of oscillator  3122  to the input of amplifier  3126 . One or more pulses provided to amplifier  3126  initiates an action to propagate energy waves  3110  having simple or complex waveforms through energy propagating structure or medium  3102 . Amplifier  3126  comprises a digital driver  3128  and matching network  3130 . In one embodiment, amplifier  3126  transforms the oscillator output of oscillator  3122  into sine waves of electrical waves  3132  having the same repetition rate as oscillator output  3124  and sufficient amplitude to excite transducer  3104 . 
     Emitting transducer  3104  converts the sine waves  3132  into energy waves  3110  of the same frequency and emits them at the first location into energy propagating structure or medium  3102 . The energy waves  3110  propagate through energy propagating structure or medium  3102 . Upon reaching transducer  3106  at the second location, energy waves  3110  are captured, sensed, or detected. The captured energy waves are converted by transducer  3106  into sine waves  3134  that are electrical waves having the same frequency. 
     Amplifier  3136  comprises a pre-amplifier  3138  and zero-cross receiver  3140 . Amplifier  3136  converts the sine waves  3134  into digital pulses  3142  of sufficient duration to sustain the behavior of the closed loop circuit. Control circuitry  3118  responds to digital pulses  3142  from amplifier  3136  by opening switch  3120  and closing switch  3144 . Opening switch  3120  decouples oscillator output  3124  from the input of amplifier  3126 . Closing switch  3144  creates a closed loop circuit coupling the output of amplifier  3136  to the input of amplifier  3126  and sustaining the emission, propagation, and detection of energy waves through energy propagating structure or medium  3102 . 
     An equilibrium state is attained by maintaining unity gain around this closed loop circuit wherein sine waves  3132  input into transducer  3104  and sine waves  3134  output by transducer  3106  are in phase with a small but constant offset. Transducer  3106  as disclosed above, outputs the sine waves  3134  upon detecting energy waves propagating to the second location. In the equilibrium state, an integer number of energy waves  3110  propagate through energy propagating structure or medium  3102 . 
     Movement or changes in the physical properties of energy propagating structure or medium  3102  change a transit time  3108  of energy waves  3110 . The transit time  3108  comprises the time for an energy wave to propagate from the first location to the second location of propagating structure  3102 . Thus, the change in the physical property of propagating structure  3102  results in a corresponding time period change of the energy waves  3110  within energy propagating structure or medium  3102 . These changes in the time period of the energy waves  3110  alter the equilibrium point of the closed loop circuit and frequency of operation of the closed loop circuit. The closed loop circuit adjusts such that sine waves  3132  and  3134  correspond to the new equilibrium point. The frequency of energy waves  3110  and changes to the frequency correlate to changes in the physical attributes of energy propagating structure or medium  3102 . 
     The physical changes may be imposed on energy propagating structure  3102  by external forces or conditions  3112  thus translating the levels and changes of the parameter or parameters of interest into signals that may be digitized for subsequent processing, storage, and display. Translation of the operating frequency into digital binary numbers facilitates communication, additional processing, storage, and display of information about the level and changes in physical parameters of interest. Similarly, the frequency of energy waves  3110  during the operation of the closed loop circuit, and changes in this frequency, may be used to measure movement or changes in physical attributes of energy propagating structure or medium  3102 . 
     Prior to measurement of the frequency or operation of the propagation tuned oscillator, control logic  3118  loads the loop count into digital counter  3150  that is stored in count register  3148 . The first digital pulses  3142  initiates closed loop operation within the propagation tuned oscillator and signals control circuit  3118  to start measurement operations. At the start of closed loop operation, control logic  3118  enables digital counter  3150  and digital timer  3152 . In one embodiment, digital counter  3150  decrements its value on the rising edge of each digital pulse output by zero-crossing receiver  3140 . Digital timer  3152  increments its value on each rising edge of clock pulses  3156 . When the number of digital pulses  3142  has decremented, the value within digital counter  3150  to zero a stop signal is output from digital counter  3150 . The stop signal disables digital timer  3152  and triggers control circuit  3118  to output a load command to data register  3154 . Data register  3154  loads a binary number from digital timer  3152  that is equal to the period of the energy waves or pulses times the value in counter  3148  divided by clock period  3156 . With a constant clock period  3156 , the value in data register  3154  is directly proportional to the aggregate period of the energy waves or pulses accumulated during the measurement operation. Duration of the measurement operation and the resolution of measurements may be adjusted by increasing or decreasing the value preset in the count register  3148 . 
       FIG. 32  is a sensor interface diagram incorporating the integrated zero-crossing receiver  2900  in a pulse multiplexing arrangement for maintaining positive closed-loop feedback in accordance with one embodiment. In one embodiment, the circuitry other than the sensor is integrated on an application specific integrated circuit (ASIC). The positive closed-loop feedback path of the circuit is illustrated by the bold line path. Initially, mux  3202  is enabled to couple one or more digital pulses  3204  to the transducer driver  2700 . Transducer driver  2700  generates a pulse sequence  3208  corresponding to digital pulses  3204 . Analog mux  3210  is enabled to couple pulse sequence  3208  to the transmitter transducer  3212 . Transducer  3212  is coupled to a medium at a first location. Transducer  3212  responds to pulse sequence  3208  and generates corresponding energy pulses  3214  that are emitted into the medium at the first location. The energy pulses  3214  propagate through the medium. 
     A receiver transducer  3216  is located at a second location on the medium. Receiver transducer  3216  captures the energy pulses  3214  and generates a corresponding signal of electrical pulses  3218 . Transducer  3216  is coupled to a mux  3220 . Mux  3220  is enabled to couple to zero-cross receiver  2900 . Electrical pulses  3218  from transducer  3216  are coupled to zero-cross receiver  2900 . Zero-cross receiver  2900  counts zero crossings of electrical pulses  3218  to determine changes in phase and frequency of the energy pulses responsive to an applied force, as previously explained. Alternatively edge-detect receiver  2800  could be used to detect propagated energy waves. Zero-cross receiver  2900  outputs a pulse sequence  3222  corresponding to the detected signal frequency. Pulse sequence  3222  is coupled to mux  3202 . Mux  3202  is decoupled from coupling digital pulses  3204  to driver  2700  upon detection of pulses  3222 . Simultaneously, mux  3202  is enabled to couple pulses  3222  to driver  2700  upon detection of pulses  3222  thereby creating a positive closed-loop feedback path. Thus, in pulse mode, zero-cross receiver  2900  is part of the closed-loop feedback path that continues emission of energy pulses into the medium at the first location and detection at the second location to measure a transit time and changes in transit time of pulses through the medium. 
       FIG. 33  is an exemplary block diagram of a propagation tuned oscillator (PTO) incorporating the zero-crossing receiver  3140  for operation in pulse mode. In particular, it illustrates closed loop measurement of the transit time of ultrasound waves within a waveguide by the operation of a propagation tuned oscillator as disclosed above. This example is for operation in pulse mode. The system can also be operated in continuous wave mode, pulse mode, and pulse-echo mode. Continuous wave mode uses a continuous wave signal. Pulse-echo mode uses reflection to direct an energy wave within the energy propagation medium. Briefly, the digital logic circuit  3146  digitizes the frequency of operation of the propagation tuned oscillator. 
     In pulse mode of operation, a sensor comprising transducer  3104 , propagating structure  3102 , and transducer  3106  is used to measure the parameter. In general, the parameter to be measured affects the properties of the propagating medium. For example, an external force or condition  3112  is applied to propagating structure  3102  that changes the length of the waveguide in a path of a propagating energy wave. A change in length corresponds to a change in transit time  3108  of the propagating wave. The length of propagating structure  3102  is measured and is converted to a force measurement by way of a known length to force relationship. One benefit of pulse mode operation is the use of a high magnitude pulsed energy wave. In one embodiment, the magnitude of the energy wave decays as it propagates through the medium. The use of a high magnitude pulse is a power efficient method to produce a detectable signal if the energy wave has to traverse a substantial distance or is subject to a reduction in magnitude as it propagated due to the medium. 
     A measurement sequence is initiated when control circuitry  3118  closes switch  3120  coupling oscillator output  3124  of oscillator  3122  to the input of amplifier  3126 . One or more pulses provided to amplifier  3126  initiates an action to propagate energy waves  3110  having simple or complex waveforms through energy propagating structure or medium  3102 . Amplifier  3126  comprises a digital driver  3128  and matching network  3130 . In one embodiment, amplifier  3126  transforms the oscillator output of oscillator  3122  into analog pulses of electrical waves  3332  having the same repetition rate as oscillator output  3124  and sufficient amplitude to excite transducer  3104 . 
     Emitting transducer  3104  converts the analog pulses  3332  into energy waves  3110  of the same frequency and emits them at a first location into energy propagating structure or medium  3102 . The energy waves  3110  propagate through energy propagating structure or medium  3102 . Upon reaching transducer  3106  at the second location, energy waves  3110  are captured, sensed, or detected. The captured energy waves are converted by transducer  3106  into analog pulses  3334  that are electrical waves having the same frequency as energy waves  3110 . 
     Amplifier  3136  comprises a pre-amplifier  3138  and zero-cross receiver  3140 . Amplifier  3136  converts the analog pulses  3334  into digital pulses  3142  of sufficient duration to sustain the behavior of the closed loop circuit. Alternatively, detection can be achieved using an edge detect receiver. Control circuitry  3118  responds to digital pulses  3142  from amplifier  3136  by opening switch  3120  and closing switch  3144 . Opening switch  3120  decouples oscillator output  3124  from the input of amplifier  3126 . Closing switch  3144  creates a closed loop circuit coupling the output of amplifier  3136  to the input of amplifier  3126  and sustaining the emission, propagation, and detection of energy waves through energy propagating structure or medium  3102 . 
     An equilibrium state is attained by maintaining unity gain around this closed loop circuit wherein pulses  3332  input into transducer  3104  and pulses  3334  output by transducer  3106  are in phase with a small but constant offset. Transducer  3106  as disclosed above, outputs the pulses  3334  upon detecting energy waves propagating to the second location. In the equilibrium state, an integer number of energy waves  3110  propagate through energy propagating structure or medium  3102 . 
     Movement or changes in the physical properties of energy propagating structure or medium  3102  change a transit time  3108  of energy waves  3110 . The transit time  3108  comprises the time for an energy wave to propagate from the first location to the second location of propagating structure  3102 . Thus, the change in the physical property of propagating structure  3102  results in a corresponding time period change of the energy waves  3110  within energy propagating structure or medium  3102 . These changes in the time period of the energy waves  3110  alter the equilibrium point of the closed loop circuit and frequency of operation of the closed loop circuit. The closed loop circuit adjusts such that pulses  3332  and  3334  correspond to the new equilibrium point. The frequency of energy waves  3110  and changes to the frequency correlate to changes in the physical attributes of energy propagating structure or medium  3102 . 
     The physical changes may be imposed on energy propagating structure  3102  by external forces or conditions  3112  thus translating the levels and changes of the parameter or parameters of interest into signals that may be digitized for subsequent processing, storage, and display. Translation of the operating frequency into digital binary numbers facilitates communication, additional processing, storage, and display of information about the level and changes in physical parameters of interest as disclosed in more detail hereinabove. Similarly, the frequency of energy waves  3110  during the operation of the closed loop circuit, and changes in this frequency, may be used to measure movement or changes in physical attributes of energy propagating structure or medium  3102 . 
       FIG. 34  is a sensor interface diagram incorporating the edge-detect receiver circuit  2800  in a pulse-echo multiplexing arrangement for maintaining positive closed-loop feedback in accordance with one embodiment. The positive closed-loop feedback of the circuit is illustrated by the bold line path. Initially, multiplexer (mux)  3402  receives as input a digital pulse  3404 , which is passed to the transducer driver  2700  to produce the pulse sequence  3408 . Analog multiplexer (mux)  3410  receives pulse sequence  3408 , which is passed to the transducer  3412  to generate energy pulses  3414 . Energy pulses  3414  are emitted into a first location of a medium. Energy pulses  3414  propagate through the medium towards a second location having a reflective surface  3416 . In the pulse-echo example, energy pulses  3414  are reflected off surface  3416  at the second location of the medium, for example, the end of a waveguide or reflector, and echoed back to the transducer  3412 . 
     The transducer  3412  proceeds to capture the reflected pulse echo. In pulsed echo mode, the transducer  3412  performs as both a transmitter and a receiver. As disclosed above, transducer  3412  toggles back and forth between emitting and receiving energy waves. Transducer  3412  captures the reflected echo pulses, which are coupled to analog mux  3410  and directed to the edge-detect receiver  2800 . The captured reflected echo pulses are indicated by electrical waves  3418 . Edge-detect receiver  2800  locks on to a leading edge of signal  3418  corresponding to the wave front of a propagated energy wave to determine changes in phase and frequency of the energy pulses  3414  responsive to an applied force, as previously explained. In the embodiment, the energy wave is a reflected pulsed energy wave. Alternatively, zero-crossing receiver  2900  can be used to detect the captured reflected echo pulses. 
     Among other parameters, edge-detect receiver  2800  generates a pulse sequence  3420  corresponding to the detected signal frequency. The pulse sequence  3420  is coupled to mux  3402  and directed to driver  2700  to initiate one or more energy waves being emitted into the medium by transducer  3412 . Pulse  3404  is decoupled from being provided to driver  2700 . Thus, a positive closed loop feedback is formed that repeatably emits energy waves into the medium until mux  3402  prevents a signal from being provided to driver  2700 . 
       FIG. 35  is an exemplary block diagram of a propagation tuned oscillator (PTO) incorporating the edge-detect receiver circuit  3440  for operation in pulse echo mode. In particular, it illustrates closed loop measurement of a transit time of reflected ultrasound waves propagating within the waveguide by the operation of a propagation tuned oscillator as disclosed above. This example is for operation in a pulse echo mode. The system can also be operated in pulse mode and a continuous wave mode. Pulse mode does not use a reflected signal. Continuous wave mode uses a continuous signal. Briefly, the digital logic circuit  3446  digitizes the frequency of operation of the propagation tuned oscillator. 
     In pulse-echo mode of operation a sensor comprising transducer  3404 , propagating structure  3402 , and reflecting surface  3406  is used to measure the parameter. In general, the parameter to be measured affects the properties of the propagating medium. For example, an external force or condition  3412  is applied to propagating structure  3402  that changes the length of the waveguide in a path of a propagating energy wave. A change in length corresponds to a change in transit time of the propagating wave. Similarly, the length of propagating structure  3402  corresponds to the applied force  3412 . A length reduction corresponds to a higher force being applied to the propagating structure  3402 . Conversely, a length increase corresponds to a lowering of the applied force  3412  to the propagating structure  3402 . The length of propagating structure  3402  is measured and is converted to force by way of a known length to force relationship. 
     Transducer  3404  is both an emitting device and a receiving device in pulse-echo mode. The sensor for measuring a parameter comprises transducer  3404  coupled to propagating structure  3402  at a first location. A reflecting surface is coupled to propagating structure  3402  at a second location. Transducer  3404  has two modes of operation comprising an emitting mode and receiving mode. Transducer  3404  emits an energy wave into the propagating structure  3402  at the first location in the emitting mode. The energy wave propagates to a second location and is reflected by reflecting surface  3406 . The reflected energy wave is reflected towards the first location. Transducer  3404  subsequently receives the reflected energy wave and generates a signal in the receiving mode corresponding to the reflected energy wave. 
     A measurement sequence in pulse echo mode is initiated when control circuitry  3418  closes switch  3420  coupling digital output  3424  of oscillator  3422  to the input of amplifier  3426 . One or more pulses provided to amplifier  3426  starts a process to emit one or more energy waves  3410  having simple or complex waveforms into energy propagating structure or medium  3402 . Amplifier  3426  comprises a digital driver  3428  and matching network  3430 . In one embodiment, amplifier  3426  transforms the digital output of oscillator  3422  into pulses of electrical waves  3432  having the same repetition rate as digital output  3424  and sufficient amplitude to excite transducer  3404 . 
     Transducer  3404  converts the pulses of electrical waves  3432  into pulses of energy waves  3410  of the same repetition rate and emits them into energy propagating structure or medium  3402 . The pulses of energy waves  3410  propagate through energy propagating structure or medium  3402  as shown by energy wave propagation  3414  towards reflecting surface  3406 . Upon reaching reflecting surface  3406 , energy waves  3410  are reflected by reflecting surface  3406 . Reflected energy waves propagate towards transducer  3404  as shown by energy wave propagation  3416 . The reflected energy waves are detected by transducer  3404  and converted into pulses of electrical waves  3434  having the same repetition rate. 
     Amplifier  3436  comprises a pre-amplifier  3438  and edge-detect receiver  3440 . Amplifier  3436  converts the pulses of electrical waves  3434  into digital pulses  3442  of sufficient duration to sustain the pulse behavior of the closed loop circuit. Control circuitry  3418  responds to digital output pulses  3442  from amplifier  3436  by opening switch  3420  and closing switch  3444 . Opening switch  3420  decouples oscillator output  3424  from the input of amplifier  3426 . Closing switch  3444  creates a closed loop circuit coupling the output of amplifier  3436  to the input of amplifier  3426  and sustaining the emission, propagation, and detection of energy pulses through energy propagating structure or medium  3402 . 
     An equilibrium state is attained by maintaining unity gain around this closed loop circuit wherein electrical waves  3432  input into transducer  3404  and electrical waves  3434  output by transducer  3404  are in phase with a small but constant offset. Transducer  3404  as disclosed above, outputs the electrical waves  3434  upon detecting reflected energy waves reflected from reflecting surface  3406 . In the equilibrium state, an integer number of pulses of energy waves  3410  propagate through energy propagating structure or medium  3402 . 
     Movement or changes in the physical properties of energy propagating structure or medium  3402  change a transit time  3408  of energy waves  3410 . The transit time  3408  comprises the time for an energy wave to propagate from the first location to the second location of propagating structure  3402  and the time for the reflected energy wave to propagate from the second location to the first location of propagating structure  3402 . Thus, the change in the physical property of propagating structure  3402  results in a corresponding time period change of the energy waves  3410  within energy propagating structure or medium  3402 . These changes in the time period of the repetition rate of the energy pulses  3410  alter the equilibrium point of the closed loop circuit and repetition rate of operation of the closed loop circuit. The closed loop circuit adjusts such that electrical waves  3432  and  3434  correspond to the new equilibrium point. The repetition rate of energy waves  3410  and changes to the repetition rate correlate to changes in the physical attributes of energy propagating structure or medium  3402 . 
     The physical changes may be imposed on energy propagating structure  3402  by external forces or conditions  3412  thus translating the levels and changes of the parameter or parameters of interest into signals that may be digitized for subsequent processing, storage, and display. Translation of the operating frequency into digital binary numbers facilitates communication, additional processing, storage, and display of information about the level and changes in physical parameters of interest. Similarly, the frequency of energy waves  3410  during the operation of the closed loop circuit, and changes in this frequency, may be used to measure movement or changes in physical attributes of energy propagating structure or medium  3402 . 
     Prior to measurement of the frequency or operation of the propagation tuned oscillator, control circuitry  3418  loads the loop count into digital counter  3450  that is stored in count register  3448 . The first digital pulses  3442  initiates closed loop operation within the propagation tuned oscillator and signals control circuit  3418  to start measurement operations. At the start of closed loop operation, control circuit  3418  enables digital counter  3450  and digital timer  3452 . In one embodiment, digital counter  3450  decrements its value on the rising edge of each digital pulse output by edge-detect receiver  3440 . Digital timer  3452  increments its value on each rising edge of clock pulses  3456 . A stop signal is output from digital counter  3450  when digital pulses  3442  has decremented the value within digital counter  3450  to zero. The stop signal disables digital timer  3452  and triggers control circuit  3418  to output a load command to data register  3454 . Data register  3454  loads a binary number from digital timer  3452  that is equal to the period of the energy waves or pulses times the value in counter  3448  divided by clock period  3456 . With a constant clock period  3456 , the value in data register  3454  is directly proportional to the aggregate period of the energy waves or pulses accumulated during the measurement operation. Duration of the measurement operation and the resolution of measurements may be adjusted by increasing or decreasing the value preset in the count register  3448 . 
       FIG. 36  is a final insert  3602  in accordance with an exemplary embodiment. In the example, the final insert  3602  is a prosthetic component for a total knee reconstruction. Insert  3602  comprises two bearing surfaces that couple to the condyles of a femur or femoral prosthetic component. A bottom surface of insert  3602  couples to a major surface of the tibial implant. The final insert  3602  is an active device for measuring a parameter of the muscular-skeletal system. A sensing module  3604  as disclosed hereinabove underlies each bearing surface of insert  3602 . In one embodiment, a contacting surface of insert  3602  couples to the bearing surface. In one embodiment, insert  3602  has a conformal surface that is similar to the bearing surface. The final insert  3602  is a permanent or quasi-permanent member of the joint prosthesis that provides long term post-operative sensing of the joint. Quasi-permanent refers to the fact that insert  3602  has a wear surface that has a finite life time that could need replacing depending on a number of factors such as life style, physical shape, and length of use. Final insert  3602  replaces a passive insert that has no sensing capability. In one embodiment, an external charging device proximally located to the knee prosthetics can inductively charge the sensing module  3604 . A super capacitor is charged in sensing module  3604  that powers the sensor and circuitry to perform the one or more measurements. Alternatively, a battery or other temporary energy storage device can be used to power sensing module  3604  and be charged with the external charging device. 
       FIG. 37  is a perspective view of sensing modules  3604  in final insert  3602  in accordance with an exemplary embodiment. Final insert  3602  is shown being separated in two halves via a horizontal cut to show sensing modules  3604 . Final insert  3602  is used in a total knee reconstruction where both knee compartments are replaced. A single sensing module  3604  would be used for a partial reconstruction. Bearing surfaces  3704  couple to a femoral prosthetic component (not shown) such that the articulating surfaces allow movement of the muscular-skeletal system. In the example, a bottom surface  3706  of the final insert  3602  aligns and couples to a tibial prosthetic component. In the example, the bottom surface  3706  is a support surface that retains insert  3602  in a fixed position relative to a mechanical axis of the leg. Furthermore, the bottom surface  3706  and a surface of the tibial prosthetic component are non-articulating. 
     Sensing modules  3604  underlie bearing surfaces  3704 . A parameter of the muscular-skeletal system is applied to the bearing surface  3704  and couples through the material of final insert  3602  to contacting surfaces  3702  of sensing modules  3604 . The bearing surfaces  3704  are typically a high strength polymer such as ultra high molecular weight polyethylene. In a non-limiting example, a force, pressure, or load is the parameter measured by sensing module  3604 . Sensing module  3604  can measure parameter magnitude and the location where the parameter is applied. Sensing module  3604  can have a surface that mirrors or replicates the surface of bearing surfaces  3704 . 
     In one embodiment, the final insert  3602  can be precision molded in two or more pieces that allow the positioning and insertion of sensing module  3604 . As shown, the final insert is formed in two halves. The upper half includes the bearing surfaces  3704 . The insert can be formed of a composite material. The composite material will at least include the bearing surface material and a second material that is attached or bonded together. A cavity is formed in predetermined locations that receive sensing modules  3604 . The cavities correspond to bearing surfaces  3604  for each compartment of the knee. The sensing modules  3604  are placed in each cavity. The halves of final insert  3602  are then fastened together whereby the contacting surface  3702  operatively couples to a corresponding bearing surface  3704 . The contact surfaces  3702  have a relational position to bearing surfaces  3604  allowing position detection where the parameter is applied. The halves of final insert  3602  can be mechanically fastened, attached by adhesive, thermally bonded, or connected by other method such that halves will not separate under all operating conditions. The fastening process can also form a seal that isolates sensing modules  3604  from the external environment. 
       FIG. 38  is an illustration of the final insert  3602  installed in a knee in accordance with an exemplary embodiment. In the example, a femoral prosthetic component  3710  is coupled to a prepared  3714  femur. Similarly, a tibial prosthetic component  3712  is coupled to a prepared tibia  3716 . The preparation includes alignment of the prosthetic components to a mechanical axis. The insert  3602  is placed between the tibial prosthetic component  3712  and femoral prosthetic component  3710 . In general, the insert  3602  is substantially equivalent in dimensions to a passive final insert. The artificial condyles of femoral prosthetic component  3710  articulate with a bearing surface of final insert  3602  that allows movement of the leg. 
     As disclosed above, final insert  3602  includes a sensing module that can transmit data to a processor  3708 . The processor can be in a tool, equipment, computer, display, or other device. As shown, the processor is in a notebook computer. Receiver circuitry is coupled to processor  3708  that can communicate with the sensing module. Typically, the receiver circuitry is placed in close proximity to final insert  3602  to receive the short-range transmission. In one embodiment, the sensing module can only transmit data. In a second embodiment, the sensing module can have two-way communication between the sensing module and processor  3708 . 
     The loading, balance, and position can be adjusted during surgery within predetermined quantitatively measured ranges through surgical techniques and adjustments using data from a trial insert and final insert  3602 . Both the trial and final inserts include the sensing module to provide measured data to processor  3708  for display. The final insert  3602  is also used to monitor the reconstructed joint long term. The data can be used by the patient and health care providers to ensure that the joint is functioning properly during rehabilitation and as the patient returns to an active normal lifestyle. Conversely, the patient or health care provider is notified when the measured parameters are out of specification. This provides early detection of a problem that can be resolved with minimal stress to the patient. The data from final insert  3602  can be displayed on a screen in real time using data from the embedded sensing module. In one embodiment, a handheld device is used to receive data from final insert  3602 . The handheld device can be held in proximity to the knee allowing a strong signal to be obtained for reception of the data. 
     In general, final insert  3602  is an example of a sensor system that can be integrated into prosthetic components. The form factor of the sensing assemblages, layout architecture, electronic circuitry, and housing allow it to fit in one or more prosthetic components. Moreover, it is a self-contained device that performs measurements without extraneous devices. The sensing module can also be placed in femoral prosthetic component  3710  or tibial prosthetic component  3712  to measure a parameter of interest. Data generated by the device can be sent to a database for analysis. 
     Artificial components for other joint replacement surgeries have a similar operational form as the knee joint example. The joint typically comprises two or more bones with a cartilaginous surface as a bearing surface that allows joint movement. The cartilage also acts to absorb loading on the joint and prevents bone-to-bone contact. Reconstruction of the hip, spine, shoulder, and other joints has similar functioning insert structures having at least one bearing surface. Like the knee joint, these other insert structures typically comprise a polymer material. The polymer material is formed for a particular joint structure. For example, the hip insert is formed in a cup shape that is fitted into the pelvis. In general, the size and thickness of these other joint inserts allow the integration of the sensing module. It should be noted that the sensing module disclosed herein contemplates use in both trial inserts and permanent inserts for the other joints of the muscular-skeletal system thereby providing quantitative parameter measurements during and post surgery. 
     While the present invention has been described with reference to particular embodiments, those skilled in the art will recognize that many changes may be made thereto without departing from the spirit and scope of the present invention. Each of these embodiments and obvious variations thereof is contemplated as falling within the spirit and scope of the invention.