Abstract:
A flexible antenna capacitively coupled to related circuitry components for an active wearable data transceiver electronic location and identification device. Wearable data transceivers (WDXs) are employed as bracelets, badges, and may be incorporated with back pack straps and clothing at locations such as collars, cuffs, and hems. They employ various colors. Active transceiver communication devices are also mounted on objects for real time location tracking and identification. Body-mounted WDXs match the body with the antenna for sending and receiving signals. WDX power includes coplanar battery cells and circuitry has radio transmitter and radio receiver components.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to flexible antenna coupling to related electronic components, and more particularly, to a capacitively coupled flexible antenna system employed in an active wireless data transceiver (WDX) device and method. 
       BACKGROUND OF THE INVENTION 
       [0002]    Many applications incorporate radio frequency identification (RFID) tags. RFID tags employ reflected energy originally transmitted from an RFID reader, and do not generate RF energy. Some Real Time Location Systems (RTLSs) track objects by associated RFID tags. For individuals, a badge is used for tracking in environments such as health-care facilities, warehouses, and other areas where location is important. These RFID personnel badges communicate with fixed or hand-held readers. These devices employ a combination of antennas and electronics. They provide structures to support and protect the antennas and electronics, and to mount or attach them to objects. In many applications size, shape and mechanical properties such as flexibility, are important but impeded. Bulky materials and construction add undue thickness and stiffness to devices. These devices require adequate electrical connections, mechanical support, and appropriate positioning of components such as connectors and antennas. Structures for these purposes can add complexity, thickness, inflexibility and cost to the RFID device. 
         [0003]    Additionally, RFID systems operate over various frequencies from high-frequency (HF) through super-high-frequency (SHF). Multiple operating issues arise in these ranges. While the performance of an RFID tag operating in the HF band may be less affected by the tag&#39;s proximity to the human body, a typical worn device is approximately 10 cm in length, including the antenna. This is a small fraction of a wavelength for the lower frequencies. Antennas which are a small fraction of a wavelength in linear dimensions are very inefficient radiators and receptors. As a result, the useful operating range for the HF band can be just a few inches from the reader antenna, significantly limiting the usefulness of HF tags. RFID systems operating at higher frequencies, however, may provide longer ranges in part because the shorter wavelength is more comparable to the antenna dimensions. This dimension match improves efficiency. However, compared to the HF band, signals at these higher frequencies are much more strongly affected by obstacles and materials in the immediate environment of the antenna due to the shorter wavelengths. Furthermore, antennas operating on or adjacent to the human body will be severely detuned and possibly rendered inoperable. Thus, the usability of these antennas in identification devices with RFID capability is very limited. When on or near the surface of a human body, the reactive near fields are influenced by the human tissue and there may be an impedance mismatch between the antenna and connected circuits, resulting in poor overall efficiency. This mismatch may detune the antenna and reduce the energy radiated away from the body, further impairing performance. 
         [0004]    Another characteristic of RFID systems is that the performance of such systems is governed by the Radar Equation (1). 
         [0000]    
       
         
           
             
               
                 
                   
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                         A 
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                        
                       σ 
                        
                       
                           
                       
                        
                       
                         F 
                         4 
                       
                     
                     
                       
                         
                           ( 
                           
                             4 
                              
                             π 
                           
                           ) 
                         
                         2 
                       
                        
                       
                         R 
                         4 
                       
                     
                   
                 
               
               
                 
                   ( 
                   1 
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         [0005]    Where P r =the power returning to the receiving antenna, P t =the transmitter power, G t =the gain of the transmitting antenna, A r =the effective aperture (area) of the receiving antenna, σ=the radar cross section or scattering coefficient of the target, F=the pattern propagation factor, and R=the range 
         [0006]    Essentially, this means that the system performance is limited by the fourth power (1/R 4 ) of the distance to the RFID tag. This is due to the fact that the RFID interrogator transmitter power needs to reflect off the RFID tag and be received by the interrogator. 
         [0007]    The above problems with RFID systems may result in limited range, difficulty simultaneously tracking multiple proximate tags, and limited information capacity. What is needed is an economical, flexible and wearable device that efficiently communicates information in support of applications such as personnel or equipment location. 
       SUMMARY OF THE INVENTION 
       [0008]    In contrast to RFID devices, the subject invention is a Wireless Data Transceiver (WDX). The WDX has, in part, a battery, RF oscillator, transmitter, receiver and antenna. The WDX generates its own RF energy. Therefore, the performance of the WDX is controlled by the square of the distance to the interrogating transceiver. Embodiments include wearable data transceiver (WDX) communication devices incorporating flexible antennas that are coupled to associated electronics. Embodiments comprise badges, wristbands or bracelets. They may be incorporated with clothing at locations such as collars, cuffs and hems and employ various colors. Frequency ranges may comprise bands of 300-347 MHz, 433 MHz, and 902-928 MHz. Standardized European bands as well as other ISM bands around 2.4 GHz and 5.8 GHz may be used in embodiments. There are also other frequency embodiments in the 7 GHz range used for ultra wide band. Other frequency bands may be used. Application environments include, but are not limited to hospitals, clinics, schools, warehouses, office building, factories, and prisons. 
         [0009]    An embodiment provides a device for communication comprising an enclosure; a flexible antenna component; and communication circuitry for generating and receiving signals, wherein the communication circuitry is in electrical communication with the antenna component and the communication circuitry and the antenna component are within the enclosure, wherein the device is an active real time location and identification device. For further embodiments, the electrical communication with the antenna component and the communication circuitry comprises capacitive coupling of the antenna to the circuitry; and the capacitive coupling comprises an adhesive affixing the antenna component to the circuitry. In another embodiment, the device is matched to a proximate body of a wearer, whereby communication performance is enhanced. For further embodiments, the enclosure is flexible; components of the enclosure are seam welded, whereby device size is reduced; or components of the enclosure are RF seam welded. Optionally, components of the enclosure are heat seam welded. In embodiments, the circuit comprises a power source and an RF oscillator. In yet further embodiments, the device is affixed to at least one of collar, hem, backpack strap, and object; and the device is disposable. For some embodiments, assembly of the circuitry and the antenna is inserted through a slot defined by the enclosure, the slot being sealed once fastened around an appendage of a wearer. For others, the assembly of the circuitry and the antenna is inserted through a slot defined by the enclosure, and the slot is sealed prior to fastening around an appendage of a wearer. In yet others, the assembly of the circuitry and the antenna is inserted through a slot defined by the enclosure prior to seam welding components of the enclosure. Additionally for some embodiments, the communication circuitry comprises an inflexible circuit board; and it comprises at least one battery coplanar with circuit board of the communication circuitry. Another embodiment comprises clips retaining the at least one coplanar battery, whereby thickness of the device is reduced. While for others the color of the device is selectable. Another embodiment provides that the device comprises a matching network at about approximately 315 MHz matching a differential transmitter output impedance of about approximately 100 ohms. 
         [0010]    Yet another embodiment provides a method of identifying a subject, comprising the steps of storing information in circuitry; placing the circuitry in electrical connection with an antenna component; inserting assembly of the circuitry and the antenna in an enclosure; attaching the enclosure to the subject to be associated with the stored information; and accessing the information in the circuitry. For other embodiments, the enclosure comprises means for attaching the enclosure to the subject, the enclosure further comprising means for retaining the assembly, wherein the retaining means comprises a resilient body portion defining an opening therein and a retaining lip adjacent the opening, whereby the opening may be deformed to permit insertion of the assembly into the body portion and the retaining lip assists in retaining the assembly in the body portion; the assembly retaining means are associated with the attaching means. Further embodiments provide that the identifying further comprises locating the subject by RF communication; and removing a tab activates the device. 
         [0011]    A further embodiment is a method for operating on electromagnetic signals using a device comprising an antenna coupled to circuitry, the method comprising the steps of positioning the device proximate an individual; coupling the device to the individual by proximity; receiving a receive signal; coupling the receive signal to the antenna; receiving the receive signal by the circuitry, wherein the circuitry is coupled with the antenna; decoding the received signal by a processor; generating transmit data; generating a transmit signal by the circuitry; coupling the transmit signal to the antenna, wherein the antenna is coupled with the circuitry; transmitting the transmit signal. In another embodiment, the coupling of the circuitry with the antenna is capacitive. 
         [0012]    The features and advantages described herein are not all-inclusive and, in particular, many additional features and advantages will be apparent to one of ordinary skill in the art in view of the drawings, specification, and claims. It should be noted that the language used in the specification has been principally selected for readability and instructional purposes, and not to limit the scope of the inventive subject matter. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    Figures are not necessarily to scale and illustrations of relative sizes, shapes and other detailed attributes of elements may be schematic rather than literal or precise. 
           [0014]      FIG. 1  is a simplified diagram of a bracelet device configured in accordance with an embodiment. 
           [0015]      FIGS. 2A-2D  are simplified diagrams of device component configurations in accordance with embodiments. 
           [0016]      FIG. 3  is a simplified exploded diagram of device component layers in accordance with one embodiment. 
           [0017]      FIG. 4A-4C  depict simplified views of device activation/deactivation embodiments. 
           [0018]      FIG. 5  is a simplified diagram of a functional schematic in accordance with one embodiment. 
           [0019]      FIGS. 6A and 6B  depict equivalent and matching circuits for device components in accordance with one embodiment. 
           [0020]      FIG. 7  is a flow chart of a method of operation in accordance with one embodiment. 
           [0021]      FIG. 8  is a simplified diagram of device body placement components in accordance with one embodiment. 
           [0022]      FIG. 9  is a simplified diagram of an operational system configuration in accordance with one embodiment. 
           [0023]      FIGS. 10  A-E are detailed illustrations of a wrist band system in accordance with one embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]    Embodiments include a wearable data transceiver (WDX) in a bracelet form. They are physically dimensioned to match existing non-active bracelets. To provide for a small form-factor, seams are RF seam welded, avoiding the bulk of adhesive-joined seams. Materials employed allow the bracelet to be created in various colors. Embodiments are packaged inside two layers of vinyl creating a soft and flexible bracelet. It comprises a flexible antenna, retaining flexibility when the assembly is inserted into the bracelet. The active circuitry is built on a rigid, inflexible, printed circuit board, but is sufficiently small to not impair bracelet functionality. The assembly of circuitry and antenna components can either be inserted through a slot which is sealed once fastened around an individual&#39;s wrist, or it can be inserted prior to welding. In embodiments, the slot remains to provide for an activation pull tab. Another embodiment may have a pull tab inside the pocket of the enclosure and no external slot. Since the bracelet is made of flexible vinyl, the tab could be pulled out of position by squeezing it through the vinyl and pulling it out of position, thus enabling the device. In embodiments, the device is affixed to a wrist, ankle, neck or other part of a person, animal or object. It may be inserted inside an article of clothing such as a pant or dress hem, point of a collar, shirt cuff, waist belt, suspenders, or jacket cuff. Embodiments are disposable following a single use. For example, the wrist band can be cut off the wrist or ankle or they can be re-usable and employ rechargeable batteries for long term operation. 
         [0025]    For embodiments, the pull tab is used with a bar coded identification number on it such that the bracelet can be scanned at check in to associate it with a hospital patient and, at the same time, pulling the tab activates the WDX device. By activating the WDX only when it is being put on the patient, battery power is saved thereby reducing the overall size of the device and extending its operational life. Batteries co-planar with the circuit board keep overall height thin, avoiding a noticeable bump. Embodiments include special battery contacts for this purpose. 
         [0026]    The antenna is tuned for optimal performance in the presence of, or contact with, the human body. This extends battery life and increases the distance and accuracy of wearable data transceiver position determination. 
         [0027]      FIGS. 1A-1E  depict simplified diagrams of a bracelet device  100  configured in accordance with an embodiment. 
         [0028]      FIG. 1A  is a side view of first component layer  105  and second component layer  110 . For embodiments, first component layer  105  and second component layer  110  materials are vinyl. In embodiments, vinyl is 0.005″ thick; however, the thickness can be changed for the particular application. A belt for a waist might be made of a material that looks like leather or may be leather. For embodiments, the thickness of the material would be adjusted to be thicker and stronger. The material could also be changed for the particular environment. For example, the WDX can be placed inside rubber gloves used to handle chemicals. 
         [0029]      FIG. 1B  shows a plan view of first and second layers attached to each other in shaded first welding region  115 . In no-weld region  120 , first component layer  105  and second component layer  110  are not attached, forming a pocket. Width of no-weld region, first width  125 , is approximately 0.87 inch minimum. Device outside width at no-weld region  120 , second width  130 , is approximately 1 inch. Device width at first welding region  115 , third width  135 , is approximately 0.6 inch. Overall device length  140  is approximately 10.85 inches. Slit  145  is provided in first component layer  105 . In embodiments, device components are inserted through slit  145 . 
         [0030]      FIG. 1C  is a plan view of device  100  with third component  150  included. Embodiments of third component  150  have dimensions of about 2.2″×0.55″ and comprises adhesive tape used to hold the device together once wrapped around the wrist. Other embodiments use different attachment methods. 
         [0031]      FIG. 1D  identifies device side view for area  155  shown in detail in  FIG. 1E . 
         [0032]      FIG. 1E  side view depicts third component  155  proximate first and second component layers  160 . For embodiments, third component  150  material is 0.002″-0.005″ thick pressure sensitive adhesive (PSA). Third component  150  PSA initially has a release liner on the surface facing first component layer  105 . This is removed to attach third component  150  to first and second component layers  105  and  110 . Slit  145  is present in third component  150  and aligned with slit  145  in first component layer  105 . In embodiments, third component  150  is adhered to first component layer  105  after welding first component layer  105  and second component layer  110 . For embodiments, third component is on the slot side of the device so that the device is sealed once assembled on a wrist. 
         [0033]      FIGS. 2A-2D  show various configurations  200  of the device with respect to the batteries, circuitry, and the antenna for embodiments of the invention. 
         [0034]      FIG. 2A  depicts use of circuit board  205 . Antenna component  210  comprises a conductive silver screen printed antenna element  215  over substrate  220  using, in embodiments, 3M™ very high bonding (VHB™) adhesive tape in region  225  to bond them together. A 0.002″ inch (467 MP from 3M™) adhesive thickness is used for embodiments. Other embodiments use 0.005″ thick VHB (468 MP from 3M™). Further embodiments use 9505 and 9502 VHB versions from 3M™. Version selection stems from the relationship of the thickness to the tuning parameters. Embodiments employ 0.005 inch thick polyester for substrate  220 . Conducting components may be metals, polymers, inks, carbon, and organic material. The ohmic loss of the material is taken into account in the design to avoid unnecessary losses. The figure also shows the use of conductive plates  230  and  235 . In embodiments, conductive plates  230  are round copper on circuit board  205 , and conductive plates  235  are conductive silver ink on substrate  220 . Plates  230  and  235  function as the plates of a capacitor, coupling antenna and circuitry components. In one embodiment, the diameter of plates is 0.25-inch, and they are separated by 0.005-inch of adhesive dielectric. Conductive plates  230  and  235  are aligned over each other, with circuit components  240  and power source  245  laterally opposite antenna component  210 . Circuit components and batteries are outside of regions  225  and  230  when assembled. The artisan will appreciate that conductive plates  230  and  235  may be shapes other than circular, and that minor misalignments of the plates will not appreciably affect the operation. Assembled length in embodiments is approximately 4 inches. In embodiments, circuit board material is Flame Retardant 4 (FR4) and thickness is 0.015 inch. Attributes include compliance with Underwriters Laboratories UL 94-V0 flammability standard. Dielectric constant properties include values of 4.7 maximum with 4.35 at 500 MHz, and 4.34 at 1 GHz. In embodiments, the antenna of the subject invention is a balanced, electrically-small loop antenna. Other antennas may be implemented, and do not necessarily have to be a loop. In the case of electrically small loop antennas, it is desirable to maximize the enclosed area of the loop. The shape of the loop, in this case, is immaterial except for maximizing its enclosed area. Matching component values were determined with device components in proximity to a body. 
         [0035]      FIG. 2B  depicts a device first side  250  and second side  255  Batteries  260  are on first side  250  and circuit components  240  on second side  255 . Leftmost battery of  260  may be omitted if the extra power capacity were not required. 
         [0036]      FIG. 2C  depicts a device first side  265  and second side  270 . Battery  275  and circuit components  240  are on first side  265  and battery  275 ′ is on second side  270 . 
         [0037]      FIG. 2D  depicts battery  280  co-planar with the illustrated circuit board segment  285  retrained by clips  290 . 
         [0038]      FIG. 3  depicts a simplified exploded diagram  300  of device component layers. Antenna element layer  305  is affixed to substrate layer  310  by adhesive  315 . For embodiments, adhesive is in coupling regions only. 
         [0039]      FIGS. 4A-4C  depict device activation and de-activation implementation embodiments  400 . In  FIG. 4A , pulling pull tab or strip  405  starts the system by operating tab switch  410  on substrate  415 . In  FIG. 4B , pushing push button  420  starts the device by operating button switch  425  on substrate  430 . In  FIG. 4C , pulling tab  435  starts the system by enabling electrical contact between battery  440  and battery clip  445 . In embodiments, battery  440  is located within an aperture in substrate  450 . For other embodiments, the device is activated by external force on the flexible enclosure, closing a circuit. For embodiments, cutting disables the device. Cutting the bracelet off at the antenna is sufficient in embodiments to stop transmissions and uses a task already employed for removing the device. For some embodiments it is not required that the device be turned off; for some embodiments the batteries will run out in a short time. 
         [0040]      FIG. 5  is a simplified diagram  500  of a functional schematic of a WDX device  505 . Flexible antenna  510  is coupled  515  to circuitry  520 . Coupling embodiments are capacitive. Circuitry  520  operates from power source  525  incorporated in WDX device  505 . WDX device  505  communicates with transceiver  530  to exchange data and establish WDX device  505  location. In embodiments, circuitry  520  components comprise microprocessor  535 , radio frequency (RF) oscillator  540 , switch  545 , RF receiver  550 , RF demodulator  555 , RF modulator  560 , and RF transmitter  565 . Each embodiment comprises a power supply and RF oscillator. Note that RF oscillator component  540  generates the RF signal for RF signal transmission, distinct from an integrated circuit clock-generating oscillator. Components may be contained within other components. Components of other various embodiments (not shown) comprise analog to digital converter (ADC), digital to analog converter (DAC), and memory. Integrated circuit component form-factors include, but are not limited to, small-outline integrated circuit (SOIC) and chip on board with an epoxy encapsulant (glob top). 
         [0041]      FIGS. 6A and 6B  depict equivalent and matching circuits, respectively, for device embodiments. 
         [0042]      FIG. 6A  depicts an equivalent circuit  600 A for a WDX device with antenna component  605  and circuitry component  610 . In embodiments, antenna component  605  and circuitry component  610  are capacitively coupled by components  615 . Antenna component  605  can be modeled as reactance  620  in series with resistor  625 . Reactance  620  represents the reactance of the antenna. Resistor  625  represents power dissipation through the losses in the antenna and in the coupled dielectric plus the radiated energy. Circuitry component  615  comprises effective source impedance  630  and effective voltage source  635  from the circuitry. 
         [0043]      FIG. 6B  depicts a matching circuit  600 B for a WDX device. TP_ANT 1   640  and TP_ANT 2   645  are the pads on the printed circuit board (PCB) which interface with the flexible antenna. The components are mirrored since the output of the transmitter (on the left side, not labeled) is a differential, balanced output; thus, only one side is described. C 12   650  of 33 pF, L 1   655  of 18 nH and C 13   660  of 22 pF form a “pi” network which serves two purposes. First, it matches the impedance of the antenna at points TP_ANT 1   640  and TP_ANT 2   645  to the transmitter output which is approximately a 100-ohm differential impedance. Secondly, it forms a low-pass filter with a cutoff frequency slightly above the intended band of operation. This filter action helps insure compliance with FCC requirements for harmonic suppression. The values shown are representative and specific to the embodiment application in the 315 MHz band. Changes in at least any of the following conditions would require different values: different operating frequency, different antenna size or shape, optimization for other than a bracelet. 
         [0044]      FIG. 7  is a flow chart  700  of a method of operation of an embodiment of the WDX device. The steps include positioning the device proximate an individual,  705 . Coupling the device to an individual by proximity,  710 . Receiving an RF signal,  715  comprising RF signal coupled to the antenna,  720 . Circuitry receives the RF signal via coupling with the antenna,  725 . Microprocessor decodes received signal data and generates data to transmit,  730 . The circuitry generates an RF signal,  735 . The RF signal is coupled to the antenna,  740 . The device transmits the RF signal,  745 . Note that the steps may be performed in alternate orders. 
         [0045]      FIG. 8  depicts particular, but not exhaustive, body locations  800  for the WDX device. Body  805  locations for device mounting include wrist  810 , garment hem  815 , waist  820 , chest  825 , and collar  830 . Nonlimiting embodiment locations include sleeve cuffs, belts, gloves, shoes, and an embodiment that attaches to the skin like an adhesive strip. 
         [0046]      FIG. 9  is a simplified diagram  900  of an operational system configuration embodiment. Transceiver  905  is in communication with multiple WDX devices, in this case within a building. WDX devices  910 ,  915 ,  920 , and  925  communicate with transceiver  905 . Additional WDX devices  930  may be operational within the facility building. In embodiments, the transceiver  905  antenna is circularly polarized to support a wearable data transceiver antenna of random linear polarization. This would avoid polarization fades. 
         [0047]      FIGS. 10  A-E are detailed scale illustrations of a wrist band system embodiment depicting circuitry and antenna components and their insertion into a wrist band enclosure. 
         [0048]      FIG. 10A  is a detailed illustration  1000 A of circuitry  1005  with pull tab  1010  and antenna  1015  components comprising assembly  1020  beside wrist band enclosure  1025 . 
         [0049]      FIG. 10B  is a detailed illustration  1000 B of assembly  1020  partially inserted into wrist band enclosure  1025 . 
         [0050]      FIG. 10C  is a detailed illustration  1000 C of assembly  1020  (not visible) within wrist band enclosure  1025  depicting pull tab  1010 . 
         [0051]      FIG. 10D  is a detailed scale illustration  1000 D of top or front of circuitry component. 
         [0052]      FIG. 10E  is a detailed scale illustration  1000 E of bottom or back of circuitry component. 
         [0053]    The foregoing description of the embodiments of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of this disclosure. It is intended that the scope of the invention be limited not by this detailed description, but rather by the claims appended hereto.