Patent Publication Number: US-2009228229-A1

Title: System and method for calibrating and driving piezoelectric transducers

Description:
BACKGROUND 
     1. Technical Field 
     The present disclosure relates generally to systems and methods of calibrating and driving piezoelectric transducers. 
     2. Description of the Prior Art 
     Piezoelectric-ultrasonic transducers have many applications including as a therapeutic treatment device for bone injuries, bone growth and healing of various conditions such as osteopenia and osteoporosis. A piezoelectric transducer is characterized by an electric equivalent circuit and also an acoustic equivalent circuit. Such ultrasonic delivery/treatment devices are tuned or calibrated to operate with a particular, unique piezo-electric ceramic transducer. A manufacturer must manually calibrate each treatment delivery device to a particular transducer and a unique transducer driving circuit must be shipped with the transducer as a matched pair. If a device fails in the field, the entire device with driving circuit and transducer must be replaced with a new pair. The transducer is specified to very tight tolerances specifically as to frequency of operation, impedance, and band-width. The tight tolerances require a great deal of manual labor to calibrate the transducer, thereby adding significant costs both to the production and to the utilization of the transducer. 
     More recently, for safety considerations, Talish et al., in U.S. Pat. No. 7,108,663 issued Sep. 19, 2006, incorporated herein by reference, disclose ultrasonic transducers configured with a timing means and interlock to automatically place an ultrasonic signal generator into a non-signal generating mode. 
     SUMMARY 
     The present disclosure relates to a system and method for tuning or calibrating and also driving a piezo-electric transducer for producing kinetic energy and in particular a piezo-electric transducer as used in ultrasonic therapy. 
     In one embodiment, the present disclosure relates to a system for at least one of calibrating and driving a piezo-electric transducer that includes a voltage supply, a processor, an electrical signal switch in electrical communication with the voltage supply, a Class F third order harmonic peaking blocking circuit segment in electrical communication with the voltage supply and with the electrical signal switch and configured to enable a drain voltage output having a time differential slope prior to signal passage through the harmonic peaking blocking circuit segment at turn-on of the switch, and wherein third order harmonics are rejected by the harmonic peaking blocking circuit;, a programmable frequency oscillator in electrical communication with the processor and that drives the switch, wherein the processor programs the frequency oscillator to establish the operating frequency of the switch, and an inductor in electrical communication with the harmonic frequency blocking circuit segment wherein the inductor is disposed to enable electrical connection in parallel with a piezo-electric kinetic energy transducer. The transducer electrically represents a parallel resonant resistive-capacitive circuit segment that is configured to receive the oscillating signal input at the operating frequency and to produce kinetic energy output. The system may further include a piezoelectric transducer electrically connected with the inductor, wherein magnitude of the time differential slope and magnitude of the drain voltage prior to switch turn on are indicative of transducer electrical operating efficiency, and wherein the processor measures, at at least a first operating frequency established via the programmable frequency oscillator, at least one of the drain voltage output and time slope differential prior to switch turn-on. 
     The system may also be configured wherein the processor measures, at at least a second operating frequency established via the programmable frequency oscillator, at least one of the drain voltage output and time slope differential prior to switch turn-on, wherein the processor compares the at least one of the drain voltage output and time slope differential prior to switch turn-on measured at the first operating frequency to the at least one of the drain voltage output and time slope differential prior to switch turn-on measured at the second operating frequency, and wherein the processor selects one of the first operating frequency and the second operating frequency as exhibiting at least one of drain voltage output and time slope differential indicative of a higher transducer electrical operating efficiency. Additionally, the system may include a memory resource enabling storage of at least one of the at least one of the drain voltage output and time slope differential prior to switch turn-on measured at the first operating frequency and the at least one of the drain voltage output and time slope differential prior to switch turn-on measured at the second operating frequency. The system may be configured wherein the processor stores in the memory resource at least one of the at least one of the drain voltage output and time slope differential prior to switch turn-on measured at the first operating frequency and the at least one of the drain voltage output and time slope differential prior to switch turn-on measured at the second operating frequency. Additionally, the system may be configured wherein one of the at least one of the drain voltage output and time slope differential prior to switch turn-on measured at the first operating frequency and the at least one of the drain voltage output and time slope differential prior to switch turn-on measured at the second operating frequency is indicative of higher transducer electrical operating efficiency. 
     In one embodiment, the system may be configured wherein the Class F third order harmonic peaking frequency blocking circuit segment precludes at least fifth order harmonics through the drain voltage. 
     In one embodiment, the system may include an ultrasonic power meter disposed in acoustic communication with the piezoelectric transducer and in electrical communication with the processor. The ultrasonic power meter may measure acoustic power of the transducer at at least the first operating frequency. The system may be configured wherein the processor associates the acoustic power of the transducer at at least the first operating frequency with the at least one of the drain voltage output and time slope differential prior to switch turn-on at at least the first operating frequency. The system may further include a memory resource enabling storage of at least one of the drain voltage output and time slope differential prior to switch turn-on measured at the first operating frequency and the acoustic power of the transducer associated with the at least first operating frequency. The system may be configured wherein the processor stores in the memory resource at least one of the at least one of the drain voltage output and time slope differential prior to switch turn-on measured at the first operating frequency and the acoustic power of the transducer associated with the at least first operating frequency. The system may also be configured wherein the ultrasonic power meter measures acoustic power of the transducer at at least the first operating frequency and the second operating frequency and wherein the processor associates the acoustic power of the transducer at at least the first operating frequency with the at least one of the drain voltage output and time slope differential prior to switch turn-on at at least the first operating frequency, and wherein the processor associates the acoustic power of the transducer at at least the second operating frequency with the at least one of the drain voltage output and time slope differential prior to switch turn-on at at least the second operating frequency. 
     Additionally, the system may be configured wherein the processor selects one of the first operating frequency and the second operating frequency as exhibiting at least one of drain voltage output and time slope differential indicative of a higher transducer electrical operating efficiency with respect to the acoustic power measured by the radiometer at the selected frequency. The system may further include a memory resource, the memory resource enabling storage of at least one of the drain voltage output and time slope differential prior to switch turn-on measured at the selected operating frequency; the associated acoustic power of the transducer at at least the selected operating frequency; and the selected operating frequency. The system may be configured wherein the processor stores in the memory resource at least one of the drain voltage output and time slope differential prior to switch turn-on measured at the selected operating frequency; the associated acoustic power of the transducer at at least the selected operating frequency; and the selected operating frequency. 
     In one embodiment, the system may further include a piezoelectric transducer electrically connected with the inductor, and a memory resource having stored therein at least one of the drain voltage output and time slope differential prior to switch turn-on measured at a selected operating frequency, an associated acoustic power of the transducer at at least the selected operating frequency, and the selected operating frequency. The system may also be configured wherein the drain voltage output and time slope differential prior to switch turn-on measured at the selected operating frequency and the associated acoustic power of the transducer at at least the selected operating frequency are selected at an operating frequency of the transducer at which the transducer operates at a higher electrical efficiency with respect to the associated acoustic power as compared to operating frequencies of the transducer other than the selected operating frequency. The system may be configured wherein the processor retrieves from the memory resource at least one of the drain voltage output and time slope differential prior to switch turn-on measured at a selected operating frequency; the associated acoustic power of the transducer at at least the selected operating frequency; and the selected operating frequency. The system may be configured wherein the processor programs the frequency oscillator to establish the selected operating frequency as the operating frequency of the electrical signal oscillator switch therein to drive the piezoelectric transducer at the selected operating frequency retrieved from the memory resource. 
     The present disclosure relates also to a method for at least one of calibrating and for at least one of calibrating and driving the piezo-electric transduce. The system includes providing a voltage supply providing power to the system. The method also includes providing a Class F third order harmonic peaking blocking circuit segment in electrical communication with the switch and with the voltage supply and configured to enable a drain voltage output having a time differential slope prior to signal passage through the harmonic frequency blocking circuit at turn-on of the switch, and wherein third order harmonics are rejected by the harmonic frequency blocking circuit segment wherein the inductor is disposed to enable electrical connection in parallel with the piezo-electric kinetic energy transducer and wherein the transducer electrically represents a parallel resonant resistive-capacitive circuit segment that is configured to receive the oscillating signal input at the operating frequency and to produce kinetic energy output. The method may include providing the piezoelectric transducer electrically connected with the inductor wherein magnitude of the time differential slope and magnitude of the drain voltage prior to turn on of the switch are indicative of electrical operating efficiency of the transducer, and measuring, at at least a first operating frequency, at least one of the drain voltage output and time slope differential prior to switch turn-on. 
     The method may include measuring, at at least second operating frequency, at least one of the drain voltage output and time slope differential prior to switch turn-on, comparing at least the drain voltage output and/or time slope differential prior to switch turn-on measured at the first operating frequency to the drain voltage output and/or time slope differential prior to switch turn-on measured at the second operating frequency, and selecting the first operating frequency or the second operating frequency as exhibiting at least one of drain voltage output and time slope differential indicative of a higher electrical operating efficiency of the transducer. 
     The method may also further include the step of providing a memory resource that enables storage of the drain voltage output and/or time slope differential prior to switch turn-on measured at the first operating frequency and/or the drain voltage output and/or time slope differential prior to switch turn-on measured at the second operating frequency. 
     The method may further include the step of storing in the memory resource the drain voltage output and/or time slope differential and/or the drain voltage output and/or time slope differential. Additionally, the method may include the drain voltage output and/or time slope differential and/or the drain voltage output and/or time slope differential being indicative of higher electrical operating efficiency of the transducer. 
     The Class F third order harmonic peaking blocking circuit segment may preclude third order harmonics through the drain voltage. The method may include the step of measuring the acoustic power of the transducer at at least the first operating frequency. The method may also include the step of associating the acoustic power of the transducer at at least the first operating frequency with the at least the drain voltage output and time slope differential prior to switch turn-on at at least the first operating frequency. 
     The method may further include the step of providing the memory resource enabling storage of at least the drain voltage output and time slope differential prior to switch turn-on measured at the first operating frequency and the acoustic power of the transducer associated with the at least first operating frequency. The method may further include the step of storing in the memory resource at least one of the drain voltage output and/or time slope differential prior to switch turn-on measured at the first operating frequency and the acoustic power of the transducer associated with the at least first operating frequency. 
     Additionally, the method may further include the step of measuring acoustic power of the transducer at at least the first operating frequency and the second operating frequency. The method may also include the steps of associating the acoustic power of the transducer at at least the first operating frequency with the drain voltage output and/or time slope differential prior to switch turn-on at at least the first operating frequency, and associating the acoustic power of the transducer at at least the second operating frequency with the drain voltage output and time slope differential prior to switch turn-on at at least the second operating frequency. Additionally, the method may further include the step of selecting the first operating frequency or the second operating frequency as exhibiting at least one of drain voltage output and time slope differential indicative of a higher transducer electrical operating efficiency with respect to the acoustic power measured at the selected frequency. 
     Furthermore, the method may further include the steps of providing the memory resource and storing in the memory resource at least the drain voltage output and/or time slope differential prior to switch turn-on measured at the selected operating frequency; and/or the associated acoustic power of the transducer at at least the selected operating frequency; and/or the selected operating frequency. 
     The method may also include a method of driving a transducer. Specifically, the method may include the steps of providing piezoelectric transducer electrically connected with the inductor and providing memory resource having stored therein at least the drain voltage output and/or time slope differential prior to turn-on of switch measured at a selected operating frequency, and/or an associated acoustic power of the transducer at at least the selected operating frequency and/or the selected operating frequency. 
     The method of driving the transducer may further include the step of selecting the drain voltage output and time slope differential prior to switch turn-on and the associated acoustic power of the transducer at at least an operating frequency of the transducer at which the transducer operates at a higher electrical efficiency with respect to the associated acoustic power as compared to operating frequencies of the transducer at other than the selected operating frequency. 
     Additionally, the method of driving the transducer may include the step of retrieving from the memory resource at least one of the drain voltage output and/or time slope differential prior to switch turn-on measured at a selected operating frequency; and/or the associated acoustic power of the transducer at at least the selected operating frequency, and the selected operating frequency. Furthermore, the method may include the step of programming the frequency oscillator to establish the selected operating frequency as the operating frequency of the switch, and driving the piezoelectric transducer at the selected operating frequency retrieved from the memory resource. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing features of the present disclosure will become more readily apparent and will be better understood by referring to the following detailed description of exemplary embodiments, which are described hereinbelow with reference to the drawing wherein: 
         FIG. 1  illustrates schematically an ultrasound treatment delivery device that includes a transducer driving circuit and that is coupled to a piezoelectric transducer as a matched pair according to the prior art. 
         FIG. 2  illustrates a schematic circuit block diagram of a calibration and driving circuit according to one embodiment of the present disclosure for calibrating and driving a piezo-electric transducer; 
         FIG. 3  illustrates a partially schematic circuit diagram of a calibration and driving circuit according to one embodiment of the present disclosure for calibrating and driving a piezo-electric transducer; 
         FIG. 4  is a table of exemplary values for a resistive-capacitive parallel equivalent circuit, both wet and dry, at various frequencies representing a piezoelectric transducer according to one embodiment of the present disclosure that are used to create the specific numerical parameters of the electrical components of the calibration or tuning circuit of  FIG. 3 ; 
         FIG. 5  is a graphical illustration of the output from a computer simulation of the method of tuning a piezoelectric transducer according to one embodiment of the present disclosure; 
         FIG. 6  is a table of numerical values for the magnitude of the electrical components in the circuit diagram of  FIG. 3 ; 
         FIG. 7  is a block diagram of the calibration process according to one embodiment of the present disclosure for calibrating a piezoelectric transducer; 
         FIG. 8  is a graphical illustration of implementation of the method of calibrating a piezoelectric transducer according to one embodiment of the present disclosure; and 
         FIG. 9  is a block diagram of the driving process according to one embodiment of the present disclosure for driving a piezoelectric transducer. 
     
    
    
     DETAILED DESCRIPTION 
     To advance the state of the art with respect to systems and methods of operating and using piezo-electric transducers, and particularly piezo-electric transducers used for ultrasonic therapy, such as transducers made from technical ceramics such as combinations of lead, zirconium and/or titanium, the present disclosure describes a system for calibrating and driving a piezo-electric transducer. 
     The present disclosure relates to a system for calibrating and/or driving a transducer which can be calibrated and driven or operated over a broader range of frequencies, the system enabling a “generic” transducer. Such a generic transducer facilitates and simplifies fabrication of the transducer and reduces manufacturing costs. The transducer may include a separate a cable and connector assembly which can be removably attached to the transducer. In one embodiment, a memory resource such as a memory chip is integrated with the transducer calibration and driving circuit or with the cable and connector assembly or supplied separately in a package. During calibration of the transducer, the acoustic power output of the transducer is measured by a radiometer which is connected to a processor such as a computer. The transducer is driven during the calibration process by substantially the same circuit that is used to drive or operate the transducer during end use application of ultrasonic therapy. Once the calibration process has been completed, the processor programs the memory resource with the appropriate parameters determined as providing optimum performance of the transducer, e.g., maximum electrical efficiency and acoustic power or efficiency, during the calibration process. The calibration process is performed for all transducers in a batch of transducers and can be automated. 
     Thus a complete batch or lot of transducers can be shipped from a facility without an associated driving circuit to which the transducer has been matched as a matched pair with close tolerances on the operating parameters. Instead, the appropriate parameters determined as providing optimum performance of the transducer during the calibration process are programmed into the memory resource that may be incorporated into the cable and connector assembly. The memory resource can be a memory chip integrated with the connector device or the memory resource may be a flash memory drive (sometimes referred to as a thumb drive or memory stick), a radiofrequency identification (RFID) tag or label, an electronic article surveillance (EAS) tag or label, a swipe card or other suitable memory resource. 
     Thus, ultrasound delivery/treatment devices, which include the substantially common transducer calibration and driving circuit, and the transducers can be shipped entirely separately from each other and not as a matched pair. Transducers can then be shipped separately. At the point of use, a doctor or other medical professional or an end user can then connect a separate transducer, having its optimum performance parameters stored on the memory resource, to a separate substantially common transducer calibration and driving circuit included within the ultrasound delivery/treatment device. The processor in the delivery/treatment device then receives information from the memory resource associated with the particular transducer and automatically calibrates itself to deliver the proper operating signal such as impedance, wet and dry, and frequency, to the driving circuit to assure optimum performance of the transducer during use, resulting in reduced power requirements for the power supply and longer battery life. Such a generic, non-precalibrated transducer that can be shipped separately from the delivery/treatment device, can be manufactured at a reduced cost as compared to a matched pair of delivery/treatment device and transducer according to the prior art. 
     Specifically, with respect to the design of the calibration and driving circuit, a third order peaking Class F peaking amplifier circuit is modified by inclusion of a piezo-electric transducer as a load. That is, the output network of a generic Class F third harmonic peaking power amplifier is assumed to be an ideal LC (inductance L, capacitance C) or transmission-line filter (linear, passive and lossless) that allows only fundamental and fifth order and higher harmonic frequencies power to pass through the load. The active device, e.g., a MOSFET is assumed to be an ideal current source or an ideal switch. 
     Referring first to  FIG. 1 , there is illustrated a matched pair of a piezoelectric transducer with a treatment delivery device with transducer driving circuit according to the prior art. More particularly, a treatment delivery device  1  that includes a transducer driving circuit incorporated therein interfaces at an interface  5  with a piezoelectric transducer  2 . Therefore, the treatment delivery device  1  that includes the transducer driving circuit and the piezoelectric transducer  2  that interfaces with the treatment delivery device  1  at interface  5  forms a matched pair  10 . 
     Referring now to the embodiments of the present disclosure as illustrated in  FIGS. 2 and 3 ,  FIG. 2  illustrates a schematic block diagram of one embodiment of a calibration and driving circuit system for a piezoelectric transducer according to the present disclosure.  FIG. 3  illustrates a partially schematic circuit diagram of the calibration and driving circuit according to one embodiment of the present disclosure for calibrating and driving a piezo-electric transducer. 
     More particularly,  FIG. 1  illustrates one embodiment of a system  100  for at least calibrating and driving a piezo-electric transducer  102  according to the present disclosure. The system  100  includes a calibration and driving electrical circuit  100 ′ that includes a voltage supply  104 , e.g., a battery or a power supply providing a voltage potential V CC , to a modified Class F third-harmonic peaking power amplifier  101 . The voltage supply  104  is coupled to the electrical circuit  100 ′ through an inductor L 1  that is in turn coupled to the circuit  100 ′ at first junction j 1 . The modified Class F third harmonic power amplifier  101  is in electrical communication with a transistor or oscillator switch  110 , e.g. a mixed oxide semi-conductor field effect transistor (MOSFET), and that is also coupled to the circuit  100 ′ at junction j 1 . Thus, the receiver/oscillator switch  110 , in turn, also is in electrical communication with the voltage supply  104 . A processor  118  controls the overall operation of the system  100 . The processor  118  includes memory  118   a  that may be internal to the processor, as shown, or the processor  118  is in electrical communication with an external memory (not shown). 
     A programmable frequency oscillator  120  is in electrical communication with the processor  118  and drives the switch  110 . The processor  118  programs the frequency oscillator  120  to establish the operating frequency of the electrical signal oscillator switch  110 , and therefore, the operating frequency of the modified Class F third-harmonic peaking power amplifier  101 . The output of the frequency oscillator  120  is a square wave voltage Vp that operates the switch  110 . 
     A resistor R 1  is coupled to the circuit  100 ′ at junction j 1 ′ between the frequency oscillator  120  and the switch  110 . The resistor R 1  is grounded at G 1 ′ and prevents the MOSFET gate of the oscillator switch  110  from floating and thus shorting the voltage supply  104 . 
     The modified Class F third-harmonic peaking power amplifier  101  includes a Class F third order harmonic peaking blocking circuit segment  101 ′ that is also in electrical communication with the voltage supply  104  and with the switch  110  and that is configured to enable a drain voltage output Vd at a second junction j 2 . 
     An inductor L 3  is in electrical communication with the harmonic frequency blocking circuit segment  101 ′ wherein the inductor L 3  is disposed to enable electrical connection in parallel with a piezo-electric transducer  102 . The transducer  102  electrically represents a parallel resistive-capacitive circuit segment  101   a ″, represented by a resistor Rp and a capacitor Cp that is configured to receive the oscillating signal input from the switch  110  at the operating frequency and to produce kinetic energy output, e.g., ultrasonic energy. The transducer  102  may be made from a material such as ceramic or other suitable material that can be characterized as an equivalent Rp and Cp circuit, Particular suitable materials include technical ceramics such as combinations of lead, zirconium and/or titanium. 
     The harmonic frequency blocking circuit segment  101 ′ includes a capacitor C 1  in series between second junction j 1  and a third junction j 3 . A second capacitor C 2  is connected in parallel with a second inductor L 2  from the third junction j 3  to a fourth junction j 4 . Thus, capacitor C 1  is electrically coupled in series at junction j 3 , with inductor L 2  and a capacitor C 2  that are coupled between junctions j 3  and j 4  in parallel. The power amplifier segment  101 ′ is coupled at a fifth junction j 5 , in series with fourth junction j 4 , to a transducer tuning segment  101 ″ wherein the piezoelectric transducer  102  and an inductor L 3  are coupled in parallel between fifth junctions j 5  and a sixth junction j 6 . The inductor L 3  is connected to ground G 2  through an impedance Z that is coupled to the circuit  100 ′ at junction j 6 . The transducer tuning segment  101 ″ is coupled at junction j 6  to an impedance Z draining to ground G 2 . Impedance Z may be a low value inductor, e.g., an inductor having an impedance value of about 400 nH, as described below with respect to  FIG. 6 . (Those skilled in the art will recognize that, and understand how, although the ground connections at G 1 , G 1 ′ and G 2  are illustrated as separate connections, the connections can be to a common ground). 
     Third order harmonics are rejected by the parallel circuit between junctions j 3  and j 4  formed by C 2  and L 2  of the harmonic frequency blocking segment  101 ′ and are monitored and measured by the processor  118  via a data sampler and analog-to-digital A/D converter  116   a  that is in electrical communication with, or an internal function of, the processor  118 . The drain voltage output Vd is thus directed to the processor  118  through the data sampler and analog-to-digital A/D converter  116   a.    
     In one embodiment, the circuit  100 ′ is completed by coupling a Class E rectifier  114  and a data sampler and analog-to-digital A/D converter  116   b  in between the junction j 6  and the processor  118 . The output of the rectifier  114  represents a voltage proportional to load voltage VL. 
     As described below, piezoelectric transducer  102  is represented by an equivalent circuit to resistive-capacitive segment  101 ″ a.  To establish the design of the circuit  100 ′, and specifically the numerical values of the various circuit parameters such as C 1 , L 1 , C 2 , L 2 , L 3 , R 1 , Z and Vcc, illustrated in  FIG. 6 , the piezoelectric transducer  102  is mathematically modeled between junction points a and b (that are electrically identical to junctions j 5  and j 6 , respectively) as equivalent to the parallel RC circuit segment  101   a ″ represented by resistor Rp and capacitor Cp. 
     Referring to  FIG. 4 , typical wet values of an exemplary nominal 1.50 MHz transducer for capacitance of capacitor Cp in nanofarads (nF) and for resistance of resistor Rp are shown over a range of frequencies f 1  . . . fn, beginning at at least a first frequency f 1  equal to 1.45 MHz and including a second frequency f 2  equal to 1.46 MHz, and extending to fn equal to 1.60 MHz. The range of frequencies f 1  . . . fn may be chosen as ± a percentage deviation from a nominal transducer operating frequency f, e.g. if the nominal transducer operating frequency f is 1.50 MHz, and the percentage deviation is 10%, the range of frequencies f 1  . . . fn would span about 1.35 MHz to about 1.65 MHz. Corresponding dry values of capacitance of capacitor Cp in nanofarads (nF) and resistance of resistor Rp at at least the first frequency f 1  equal to 1.45 MHz and the second frequency j 2  equal to 1.46 MHz. The wet values of Cp and Rp are the values exhibited by the transducer when placed in water. The dry values of Cp and Rp are the values exhibited by the transducer when placed in air. Using a circuit simulation program such as PSPICE (e.g., Cadence PCB design software by EMA Design Automation, Inc., Rochester, N.Y., USA), the system  100  is simulated wherein the circuit  100 ′ is assumed to be coupled to a “phantom” transducer that is represented by the parallel resonant resistive-capacitive circuit segment  101   a ″, represented by the resistor Rp and capacitor Cp connected in parallel, as shown by dashed lines in  FIG. 3 . 
       FIG. 5  illustrates a graphical output of a PSPICE simulation of the system  100  with third-harmonic Class F peaking power amplifier  101  depicted in  FIG. 3  with circuit parameter values of Cp and Rp from  FIG. 4  at f=1.45 Mhz. Represented graphically are the drain voltage Vd of the switch  110  (e.g., MOSFET), the load voltage VL (across L 3 ) and the drive signal voltage Vp of the switch  110 . The various circuit parameters such as C 1 , L 1 , C 2 , L 2 , L 3 , R 1 , Z and Vcc, illustrated in  FIG. 6  are then determined based on the PSPICE simulation. For other operating frequencies, (e.g., 1 Mhz, 3 Mhz or 5 Mhz) the circuit parameter values such as C 1 , L 1 , C 2 , L 2 , L 3 , R 1 , Z and Vcc determined in  FIG. 6  will be different and can be calculated by one skilled in the art. 
       FIG. 7  illustrates a block diagram of the system  100  for at least calibrating and driving a piezoelectric transducer as illustrated previously in  FIGS. 2 and 3 . The system  100  is shown during the calibration process and is substantially similar to the system as shown in  FIGS. 2 and 3  except that transducer module  122  is shown with generic transducer  102  coupled to the calibration and driving circuit  100 ′ with Class F amplifier  101 . An ultrasonic power meter (radiometer)  130  is disposed in acoustic communication with the piezoelectric transducer  102  and in electrical communication with the processor  118 . Transducer module  122  includes a connector assembly  124  and may be configured with a cable  126  that is in electrical communication with the transducer  102 . A memory resource  128  is shown associated with the connector assembly  124 . 
     The connector assembly  126  interfaces with the electrical circuit  100 ′ at interface  125 . In  FIG. 2 , the interface includes the junction points a and b, discussed above, and a junction point c for the memory resource  128 . The memory resource  128  may be a memory chip integrated with the connector assembly  124  and/or the cable  126  or with the transducer  102 . Alternatively, the memory resource  128  may be an independent flash memory drive (sometimes referred to as a thumb drive or memory stick), a radiofrequency identification (RFID) tag or label, an electronic article surveillance (EAS) tag or label, a swipe card or other suitable memory resource. 
     The radiometer  130 , such as an OHMIC Ultrasound Power Meter, Model UPM-DT-1, Ohmic Instruments, Easton Md., USA, or equivalent, is configured to measure acoustic power of the transducer  102  at at least a first operating frequency f 1  established via the programmable frequency oscillator  120 , and in one embodiment, over a range of frequencies, such as illustrated in  FIG. 4 . The acoustic power of the transducer at at least the first operating frequency f 1  is read by the processor  118  as one of the acoustic parameters  130 a provided to the processor  118  by the radiometer  130 . 
     Referring also to  FIGS. 7 and 8 , in addition to  FIG. 9 , the general operation of the system  100  will be explained for the determination of the magnitude of the drain voltage time differential slope ΔVd/Δt and magnitude of the drain voltage Vd prior to turn on of the oscillator switch  110 , which are indicative of electrical operating efficiency. The processor  118  measures, at at least a first operating frequency f 1  established via the programmable frequency oscillator  120 , at least the drain voltage output Vd and/or the drain voltage time differential slope ΔVd/Δt prior to turn-on of the switch  110 . The drain voltage differential ΔVd and the time differential Δt are defined as the difference between drain voltage Vd 1  at time t 1  and drain voltage Vd 2  at time t 2  wherein time t 2  is the time of turn on of switch  110  and time t 1  is a time just prior to turn-on of switch  110 . Thus, ΔVd=Vd 1 −Vd 2  and Δt=t 1 −t 2 . So the slope of the drain voltage time differential can be represented by equation (1) as follows: 
       Δ Vd/Δt =( Vd 1 −Vd 2)/( t 1 −t 2)   (1) 
     For an exemplary case of sampling data readings for a nominal 1.5 MHz piezo-electric transducer, having a quarter cycle of  165  nanoseconds, the processor  118  instructs the sampler and A/D converter  116 a to acquire four A/D data samples of Vd 1  and Vd 2  in a time period between the first time t 1  and the second time t 2  that is less than 165 nanoseconds. 
     The greater the slope represented by ΔVd/Δt, the greater the electrical efficiency of the transducer because the drain voltage Vd is minimized at the time t 2  of turn-on of the switch  110 . Those skilled in the art will recognize that although simply second drain voltage Vd 2  and the second time t 2  can be considered as representing electrical efficiency and data acquired solely for those parameters without consideration of the first drain voltage Vd 1  and the first time t 1 , the slope ΔVd/Δt provides enhanced insight into performance of the transducer  102 . 
     The processor  118  measures, at at least a second operating frequency f 2  established via the programmable frequency oscillator  120 , at least the drain voltage output Vd and time slope differential ΔVd/Δt prior to switch turn-on. The processor  118  compares at least the drain voltage output Vd and/or time slope differential ΔVd/Δt prior to switch turn-on measured at the first operating frequency f 1  to at least the drain voltage output Vd and/or time slope differential ΔVd/Δt prior to switch turn-on measured at the second operating frequency f 2 . The processor  118  selects one of the operating frequencies f 1  or f 2  as exhibiting at least drain voltage output Vd and time slope differential ΔVd/Δt as being indicative of a higher transducer electrical operating efficiency or at least a decreased electrical power input. 
     The processor  118  also associates the acoustic power of the transducer  102  at at least the first operating frequency f 1  with at least the drain voltage output Vd 1  and time slope differential prior to switch turn-on at at least the first operating frequency f 1 . 
     The processor  118  then compares at least the drain voltage output Vd 1  or time differential slope ΔVd/Δt prior to switch turn-on measured at the first operating frequency f 1  to at least the drain voltage output Vd 1  or time slope differential ΔVd/Δt prior to switch turn-on measured at the second operating frequency f 1 . In one embodiment, the processor  118  also sweeps over a range of frequencies f, such as f 1  to fn (or fmin to fmax). The processor  118  then selects, as appropriate, either the first operating frequency f 1  or the second operating frequency f 2  to fn as exhibiting at least drain voltage output Vd and/or time differential slope ΔVd/Δt indicative of a higher transducer electrical operating efficiency at the associated acoustic power for that selected frequency. During the calibration process, the processor  118  stores the acquired data readings of frequencies f, drain voltage Vd and time differential slope ΔVd/Δt, and associated acoustic power in an internal or external memory  118   a  for retrieval during the selection process. 
     The acquired data readings of frequencies f, drain voltage Vd and time differential slope ΔVd/Δt become the electrical parameters  102   a  characteristic of the transducer  102 . The processor  118  also associates the readings of acoustic parameters  130   a,  e.g., the acoustic power of the transducer  102 , acquired from the radiometer  130 , with the electrical parameters  102   a  to become the transducer parameters  132  characteristic of the transducer  102 . The transducer parameters  132  may be associated with the serial number of the particular transducer that has been calibrated and the serial number together with the transducer parameters  132  may be stored in the memory resource  128 . 
     The calibration process is performed both for the transducer  102  being subjected to wet conditions, e.g., in water, and dry conditions, e.g., in air. The transducer parameters  132  thus may be further differentiated by the readings under wet conditions, representative of proper treatment with gel in place between the transducer and the subject or patient, and the readings under dry conditions which are indicative of lack of gel in place between the transducer and the subject or patient. The transducer parameters  132  stored in the processor memory  118   a  and/or the memory resource  128  thus may include the readings under wet conditions and the readings under dry conditions. In one embodiment, the processor  118  selects the transducer parameters  132  that are indicative of higher transducer relative electrical operating efficiency. The memory resource  128  enables storage of at least the drain voltage output Vd and/or time slope differential ΔVd/Δt prior to switch turn-on measured at the selected operating frequency f; and/or the associated acoustic power of the transducer  102  at at least the selected operating frequency f, and the selected operating frequency f. 
     The processor  118  may also store in the memory resource  128  treatment compliance limits  134  for the particular transducer and ultrasonic therapy regimen. The processor  118  may set appropriate alarm limits based on actual usage of the transducer by the subject or test object, or by a medical professional, with respect to the compliance limits. The alarm limits may be set by the processor  118  to trigger one or more alarms  136  in electrical communication with the processor  118 . 
     The system  100  may also include one or more gel sensors  138 . In actuality, the gel sensors  138  are not hardware components. Rather, the presence of gel is detected by the processor  118  determining that the operating characteristics of the transducer  102  at a particular operating frequency f are representative of the dry values of Rp and Cp of transducer  102 . Upon making such a determination, the processor  118  triggers the alarm  136  based on lack of proper gel in contact with the skin during treatment. In addition to compliance limits, the alarms may include low or high power supply voltage Vcc or current. 
       FIG. 9  illustrates the system  100  during the driving process according to one embodiment of the present disclosure for driving a generic piezoelectric pressure transducer  102 . The system  100  may be the very same system  100  used to calibrate the transducer  102  by a supplier or the system  100  may be a different system  100  that is configured substantially as a standardized calibration and driving system for the transducer  102 . Similarly, the transducer  102  may be a standardized generic transducer or the same transducer calibrated by the system  100  during a calibration process. The transducer  102  is placed in contact with a subject or a test object  140  through a gel coupling  142 . 
     In particular, during the driving process, a piezoelectric transducer  102  is electrically connected to the calibration and driving circuit  100 ′ by connecting with the with the inductor L 3  at junction points a and b (see  FIGS. 2 and 3 ). Also provided is a memory resource  128  that has stored therein the transducer parameters  132  that may include at least the drain voltage output Vd and/or time slope differential ΔVd/Δt prior to switch turn-on measured at a selected operating frequency f and/or an associated acoustic power of the transducer  102  at at least the selected operating frequency f and/or the selected operating frequency f. The selected operating frequency f may be indicative of the transducer operating at a higher electrical efficiency with respect to the associated acoustic power as compared to operating frequencies of the transducer  102  other than the selected operating frequency f. 
     The processor  118  then retrieves from the memory resource  128  at least the drain voltage output Vd and/or the time slope differential ΔVd/Δt prior to switch turn-on measured at the selected operating frequency f and/or the associated acoustic power of the transducer  102  at at least the selected operating frequency f, and/or the selected operating frequency f. 
     The processor  118  then programs the frequency oscillator  120  to establish the selected operating frequency f as the operating frequency of the electrical signal oscillator switch  110  therein to drive the piezoelectric transducer  102  at the selected operating frequency retrieved from the memory resource  128 . 
     The processor  118  monitors usage of the transducer by the subject or test object  140  against the compliance limits  134  and, when appropriate, triggers the alarm(s)  136 . 
     Those skilled in the art will recognize that during the driving process of the transducer  102 , the processor  118  may also measure the drain voltage output Vd and/or the time slope differential ΔVd/Δt prior to turn-on of the oscillator switch in the same manner as described above for the calibration process with respect to  FIG. 7 . In one embodiment, an ultrasonic power meter, such as radiometer  130 , which may be portable, may disposed in acoustic communication with the piezoelectric transducer  102 , as described above with respect to  FIG. 7 , to implement the calibration process. 
     Referring again to  FIGS. 2-9 , those skilled in the art will recognize that the present disclosure relates also to a method for at least one of calibrating and driving a piezo-electric transducer, e.g., piezoelectric transducer  102 . The method includes the step of providing the system  100  for at least one of calibrating and driving the piezo-electric transducer  102 . The system  100  includes providing voltage supply  104 , e.g., Vcc providing power to the system  100 . The method also includes providing the Class F third order harmonic peaking blocking circuit segment  101 ′ in electrical communication with the switch  110  and with the voltage supply  104  and configured to enable drain voltage output Vd having time differential slope ΔVd/Δt prior to signal passage through the harmonic frequency blocking circuit  101  at turn-on of the oscillator switch  110 , and wherein third order harmonics are rejected through the drain voltage output Vd at junction j 2  and inductor L 3  in electrical communication with the harmonic frequency blocking circuit segment  101 ′ wherein the inductor L 3  is disposed to enable electrical connection in parallel with the piezo-electric kinetic energy transducer  102  and wherein the transducer  102  electrically represents a parallel resonant resistive-capacitive circuit segment  101   a ″ that is configured to receive the oscillating signal input at the operating frequency f and to produce kinetic energy output. The method may include providing the piezoelectric transducer  102  electrically connected with the inductor L 3  wherein magnitude of the time differential slope ΔVd/Δt and magnitude of the drain voltage Vd prior to turn on of the switch  110  are indicative of electrical operating efficiency of the transducer  102 , and measuring, at at least a first operating frequency f 1 , at least one of the drain voltage output Vd and time slope differential ΔVd/Δt prior to switch turn-on. 
     The method may include measuring, at at least second operating frequency f 2 , at least one of the drain voltage output Vd and time slope differential ΔVd/Δt prior to switch turn-on, comparing at least the drain voltage output Vd and/or time slope differential ΔVd/Δt prior to switch turn-on measured at the first operating frequency f 1  to the drain voltage output Vd and/or time slope differential ΔVd/Δt prior to switch turn-on measured at the second operating frequency f 2 , and selecting the first operating frequency f 1  or the second operating frequency f 2  as exhibiting at least one of drain voltage output Vd and time slope differential ΔVd/Δt indicative of a higher electrical operating efficiency of the transducer  102 . 
     The method may also further include the step of providing memory resource  128  that enables storage of the drain voltage output Vd and/or time slope differential (ΔVd/Δt) prior to switch turn-on measured at the first operating frequency f 1  and/or the drain voltage output Vd and/or time slope differential ΔVd/Δt prior to switch turn-on measured at the second operating frequency f 2 . 
     The method may further include the step of storing in the memory resource  128  the drain voltage output Vd and/or time slope differential ΔVd/Δt and/or the drain voltage output Vd and/or time slope differential ΔVd/Δt. Additionally, the method may include the drain voltage output Vd and/or time slope differential ΔVd/Δt and/or the drain voltage output Vd and/or time slope differential ΔVd/Δt being indicative of higher electrical operating efficiency of the transducer  102 . 
     The Class F third order harmonic peaking blocking circuit segment precludes third order harmonics through the drain voltage Vd. The method may include the step of measuring the acoustic power of the transducer  102  at at least the first operating frequency f 1 . The method may also include the step of associating the acoustic power of the transducer  102  at at least the first operating frequency f 1  with the at least the drain voltage output Vd and time slope differential ΔVd/Δt prior to switch turn-on at at least the first operating frequency f 1 . 
     The method may further include the step of providing the memory resource  128  enabling storage of at least the drain voltage output Vd and time slope differential ΔVd/Δt prior to switch turn-on measured at the first operating frequency f 1  and the acoustic power of the transducer  102  associated with the at least first operating frequency f 1 . The method may further include the step of storing in the memory resource  128  at least one of the drain voltage output Vd and/or time slope differential ΔVd/Δt prior to switch turn-on measured at the first operating frequency f 1  and the acoustic power of the transducer  102  associated with the at least first operating frequency f 1 . 
     Additionally, the method may further include the step of measuring acoustic power of the transducer  102  at at least the first operating frequency f 1  and the second operating frequency f 1 . The method may also include the steps of associating the acoustic power of the transducer  102  at at least the first operating frequency f 1  with the drain voltage output Vd and/or time slope differential ΔVd/Δt prior to switch turn-on at at least the first operating frequency f 1 , and associating the acoustic power of the transducer  102  at at least the second operating frequency f 2  with the drain voltage output Vd and time slope differential ΔVd/Δt prior to switch turn-on at at least the second operating frequency f 2 . Additionally, the method may further include the step of selecting the first operating frequency f 1  or the second operating frequency f 2  as exhibiting at least one of drain voltage output Vd and time slope differential ΔVd/Δt indicative of a higher transducer electrical operating efficiency with respect to the acoustic power measured at the selected frequency f. 
     Furthermore, the method may further include the steps of providing the memory resource  128  and storing in the memory resource  128  at least the drain voltage output Vd and/or time slope differential ΔVd/Δt prior to switch turn-on measured at the selected operating frequency f; and/or the associated acoustic power of the transducer  102  at at least the selected operating frequency f; and/or the selected operating frequency f. 
     The method may also include a method of driving a transducer. Specifically, the method may include the steps of providing piezoelectric transducer  102  electrically connected with the inductor L 3  and providing memory resource  128  having stored therein at least the drain voltage output Vd and/or time slope differential ΔVd/Δt prior to turn-on of switch  102  measured at a selected operating frequency f, and/or an associated acoustic power of the transducer  102  at at least the selected operating frequency f and/or the selected operating frequency f. 
     The method of driving the transducer may further include the step of selecting the drain voltage output Vd and time slope differential ΔVd/Δt prior to switch turn-on and the associated acoustic power of the transducer  102  at at least an operating frequency f of the transducer  102  at which the transducer  102  operates at a higher electrical efficiency with respect to the associated acoustic power as compared to operating frequencies of the transducer  102  at other than the selected operating frequency. 
     Additionally, the method of driving the transducer may include the step of retrieving from the memory resource  128  at least one of the drain voltage output Vd and/or time slope differential prior to switch turn-on ΔVd/Δt measured at a selected operating frequency f; and/or the associated acoustic power of the transducer  102  at at least the selected operating frequency f, and the selected operating frequency f. Furthermore, the method may include the step of programming the frequency oscillator  120  to establish the selected operating frequency f as the operating frequency of the switch  110 , and driving the piezoelectric transducer  102  at the selected operating frequency f retrieved from the memory resource  102 . 
     While several embodiments of the disclosure have been shown in the drawings and/or discussed herein, it is not intended that the disclosure be limited thereto, as it is intended that the disclosure be as broad in scope as the art will allow and that the specification be read likewise. Therefore, the above description should not be construed as limiting, but merely as exemplifications of particular embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.