Patent Description:
Given the 3D structure of the antenna and the size and weight of the battery, the RF tracking tag is made to be mechanically rigid, typically having a hard enclosure to provide protection to the antenna, electronics and battery. Although this enclosure is protective, its rigid nature also makes it fragile when exposed to bending forces since it breaks rather than flexes.

All known microwave patch antennas are driven "single-ended" or "unbalanced" and most have propagation patterns biased unidirectionally toward the normal axis of the patch. Thus, type of biased propagation pattern is not suitable for use within RF tracking tags. Further, RF tracking tag transceiver input and output circuits are often "balanced" or "differential" or "complementary" owing to the internal structure of the integrated circuit technology. Therefore, to use the traditional microwave patch antenna, a "balun" device (Balanced-to-unbalanced converter) is required to translate balanced to unbalanced (single-ended) RF currents for delivery to the traditional microwave patch antenna. The balun causes loss that results in reduced transceiver performance and reduced operational range, or requires additional power and associated size increase of a battery providing the power, making the microwave patch antenna even less suitable for use in RF tracking tags.

From <CIT> is already known a planar flexible radio-frequency (RF) tag for use in a real-time location system, comprising:.

From <CIT> is further already known a planar flexible radio-frequency (RF) tag comprising a rechargeable battery for powering a RF transmitter circuit, a microcontroller circuit, and a flexible waterproof enclosure that encapsulates the flexible substrate, an antenna patch, an RF transmitter circuit, the microcontroller circuit, and the rechargeable battery.

From <CIT> is further already known a planar flexible radio-frequency (RF) tag comprising:.

<CIT> discloses a planar flexible RF tag with first and second antenna patches being positioned on a first side of a flexible substrate and a differential input to which the differential output of an RF transmitter circuit is electrically coupled.

<CIT> discloses a planar RF tag for use in a real-time location system with first and second antenna patches and a differential input disposed on a dielectric substrate and an RF transmitter circuit having a differential output electrically coupled to the differential input.

However, there is no mention in the cited prior art of simultaneous charging and RF transmitter function of patch antennas or antenna patches, let alone "a planar complementary patch antenna" having "first and second antenna patches".

When using electronic ultra-wideband (UWB) radio frequency (RF) tags to track individuals, such as athletes, it is necessary to make the electronics as small, unobtrusive, and robust as possible, while maintaining performance of the UWB RF tags. This is provided by the planar flexible radio-frequency (RF) tag for use in a real-time location system according to claim <NUM>. The embodiments hereof include a real-time location system RF tag that has a flat, flexible, and waterproof form factor that is ideal for integration into athletic uniforms, equipment and other clothing. Embodiments include nonelectrical contact rechargeable battery system and an antenna with a propagation pattern optimized for sports tracking. Within the document is also a description of the external battery charger.

In one embodiment, a planar flexible UWB RF antenna includes a flexible non-electrically-conductive substrate and an antenna patch having electrically conductive metal positioned on one side of the flexible non-electrically-conductive substrate and having geometry defining a wirelessly transmitted UWB signal.

In another embodiment, a planar complementary patch antenna includes a flexible non-electrically-conductive substrate, first and second antenna patches positioned apart from each other on one side of the flexible non-electrically-conductive substrate, and a differential input having (a) a first feed element electrically coupled directly to only the first antenna patch and (b) a second feed element electrically coupled directly to only the second antenna patch, the differential input being drivable from a differential output of an RF transmitter circuit to generate a wireless signal from the complementary patch antenna.

In another embodiment, a dual-purpose antenna includes a first electrically conductive metal antenna element and a second electrically conductive metal antenna element configured such that: the dual-purpose antenna transmits a wireless signal at transmission frequency and propagation pattern defined by geometry of the first and second antenna elements, and the dual-purpose antenna receives, without electrical contact, capacitive power across two different capacitors each formed in part by a different one of the first and second antenna elements.

In another embodiment, a planar flexible RF tag for use in a real-time location system includes a flexible substrate, at least one antenna patch 2a' formed on a first side of the flexible substrate, an RF transmitter circuit electrically coupled to the at least one antenna patch and formed on a second side of the flexible substrate, and a microcontroller circuit formed on the second side and electrically coupled to control the RF transmitter circuit to drive the at least one antenna patch to transmit a radio signal.

In another embodiment, a planar flexible RF tag for use in a real-time location system includes a flexible substrate, first and second antenna patches formed as complementary plates on a first side of the flexible substrate, an RF transmitter circuit electrically coupled to the first and second antenna patches and formed on a second side of the flexible substrate, a microcontroller circuit formed on the second side and electrically coupled to control the RF transmitter circuit to drive the first and second antenna patches to transmit a radio signal, and a battery for powering the RF transmitter circuit and the microcontroller circuit.

In another embodiment, a planar UWB patch antenna for receiving electrical power includes a non-electrically-conductive substrate, first and second antenna patches positioned on a first surface of the non-electrically-conductive substrate and having a geometry to transmit an UWB wireless signal, a first decoupling circuit directly electrically connected to the first antenna patch and having a decoupling frequency that is different from a transmitting frequency of the UWB wireless signal, and a second decoupling circuit directly electrically connected to the second antenna patch and having the same decoupling frequency as the first decoupling circuit. The first and second decoupling circuits transferring power from the first and second antenna patches when the first and second antenna patches receive capacitive power from an external non-electrical contact charger operating at the decoupling frequency and having two metal plates of similar geometry to the first and second antenna patches and that are positioned proximate and aligned with the first and second antenna patches.

In another embodiment, a charging device for a flexible planar RF tag that has a rechargeable battery and two antenna patches includes a dielectric layer, a first and second metal plates formed on the dielectric layer and having geometry corresponding to geometry of the two antenna patches, a variable oscillator, a first inductor electrically coupled to the first metal plate and a first output of the variable oscillator, a second inductor electrically coupled to the second metal plate and a second output of the variable oscillator, and a microcontroller electrically coupled to the variable oscillator. When positioned such that the first and second metal plates are adjacent and aligned with the two antenna patches with the dielectric layer therebetween, the microcontroller is configured to control the variable oscillator to drive the first and second metal plates and transfer power to the flexible planar RF tag.

<FIG> is a schematic illustrating one example of a planar flexible RF tag <NUM> for use with a real-time location system, in embodiments. Planar flexible RF tag <NUM> includes one antenna patch <NUM> that electrically connects to a balun <NUM> that in turn electrically connects to a differential output <NUM> of an RF transceiver circuit <NUM>. A rechargeable battery <NUM> provides power to RF transceiver circuit <NUM> and to a microcontroller circuit <NUM>. In one embodiment, RF transceiver circuit <NUM> may be implemented as only a transmitter. Microcontroller circuit <NUM> controls RF transceiver circuit <NUM> via one or more electrical connections. Planar flexible RF tag <NUM> includes a connector <NUM> for charging rechargeable battery <NUM>, and may further include a charging regulator circuit <NUM> to regulate electrical power received from connector <NUM> to charge rechargeable battery <NUM>.

In one embodiment, electrical power is regulated prior to connector <NUM>, wherein charging regulator circuit <NUM> is omitted. Antenna patch <NUM>, rechargeable battery <NUM>, microcontroller circuit <NUM>, RF transceiver circuit <NUM> and charging regulator circuit <NUM> may be enclosed within a permanently sealed enclosure <NUM> that is waterproof, wherein connector <NUM> is configured with enclosure <NUM> to allow charging of rechargeable battery <NUM> without opening of enclosure <NUM>. For example, connector <NUM> may be a waterproof type electrical connector that is permanently sealed within an orifice of enclosure <NUM>, such that enclosure <NUM> is waterproof irrespective of whether connector <NUM> is in use. In another embodiment, connector <NUM> is external to enclosure <NUM>, which is sealed around the electrical connections running between connector <NUM> and charging regulator circuit <NUM> and/or rechargeable battery <NUM>. In one embodiment, charging regulator circuit <NUM> and connector <NUM> are omitted and rechargeable battery <NUM> is replaced with a one-time use, long life, flexible battery.

<FIG> is a perspective view of the planar flexible RF tag <NUM> of <FIG>, in an embodiment. Planar flexible RF tag <NUM> is shown within a permanently sealed enclosure <NUM> that is for example a permanently sealed, thin flexible plastic packaging that allows for inclusion of planar flexible RF tag <NUM> into pockets of, and/or sewn into, clothing, uniform fabric, and other attire of the individual. For example, enclosure <NUM> may include provision for attachment such as areas for sewing, loops, button holes, and the like. The sealed nature of enclosure <NUM> allows for operation of planar flexible RF tag <NUM> in wet or dirty conditions as well as being amenable to washing. For example, additional sealing <NUM> may be used proximate and/or around connector <NUM> to prevent ingress of moisture. Antenna patch <NUM> and electrical components of planar flexible RF tag <NUM> are positioned on a flexible substrate <NUM> that is contained by enclosure <NUM>, such that planar flexible RF tag <NUM> is pliable. In one embodiment, antenna patch <NUM> is formed of conductive metal positioned on one side of flexible substrate <NUM>, which is non-electrically-conductive, and antenna patch <NUM> has geometry defining transmission of a wireless UWB signal. The geometry of antenna patch <NUM> is selected to transmit the wireless UWB signal with a propagation pattern suitable for use in a real-time location system. Although shown as rectangular, the geometry of antenna patch <NUM> is selected to obtain the desired propagation pattern and transmit at a desired frequency. <FIG> also shows an orientation reference <NUM> that is relative to the physical embodiment of planar flexible RF tag <NUM>. However, planar flexible RF tag <NUM> may have no orientation restrictions when geometry of antenna patch <NUM> is symmetrical (e.g., square).

<FIG> shows a cross section A-A of the planar flexible RF tag <NUM> of <FIG> and <FIG>, in an embodiment. Antenna patch <NUM> is positioned on a first side of a flexible substrate <NUM>, and electrical components <NUM> including balun <NUM>, charging regulator circuit <NUM> (if included), microcontroller circuit <NUM>, and RF transceiver circuit <NUM>, and rechargeable battery <NUM> are positioned on a second side, opposite the first side, of flexible substrate <NUM> as shown. Rechargeable battery <NUM> is flat and flexible. In one embodiment, rechargeable battery <NUM> is a thin flexible rechargeable lithium polymer battery from BrightVolt Inc. Flexible substrate <NUM>, antenna patch <NUM>, components <NUM>, and rechargeable battery <NUM> are all contained within enclosure <NUM>. Planar flexible RF tag <NUM> is thus thin and flexible in format, allowing it to be used in place of conventional RF tags and further where the hard-potted enclosure of conventional RF tags prohibit their use.

<FIG> is a schematic illustrating one exemplary planar flexible RF tag <NUM>. Planar flexible RF tag <NUM> includes two antenna patches <NUM>(<NUM>), (<NUM>), each electrically connected to its own decoupling circuit <NUM>(<NUM>), (<NUM>) that in turn electrically connects to its own full wave rectifier half <NUM> and <NUM>, respectively. Antenna patches <NUM>(<NUM>) and <NUM>(<NUM>) cooperate to form a planar complementary patch antenna <NUM> that has a differential input <NUM>. Full wave rectifier halves <NUM> and <NUM> each include two Schottky diodes <NUM>(<NUM>)-(<NUM>) that are configured as shown in <FIG> to form a full wave rectifier having an output that electrically connects to a charging regulator circuit <NUM>. Output from charging regulator circuit <NUM> electrically connects with a rechargeable battery <NUM>. Rechargeable battery <NUM> provides power to a microcontroller circuit <NUM> and an RF transceiver circuit <NUM>. In one embodiment, RF transceiver circuit <NUM> may implement only the transmitter. RF transceiver circuit <NUM> has a differential output <NUM> that has two balanced outputs that each connect to a different input of differential input <NUM> of planar complementary patch antenna <NUM>. That is, outputs of RF transceiver circuit <NUM> each independently electrically connect to a different one of antenna patches <NUM>(<NUM>) and <NUM>(<NUM>). Microcontroller circuit <NUM> controls RF transceiver circuit <NUM> via one or more electrical connections. Antenna patches <NUM>, decoupling circuits <NUM>, full wave rectifier halves <NUM>, <NUM>, charging regulator circuit <NUM>, rechargeable battery <NUM>, microcontroller circuit <NUM> and RF transceiver circuit <NUM> may be enclosed within a permanently sealed enclosure <NUM> that is waterproof.

<FIG> is a schematic illustrating one example charging device <NUM> for charging rechargeable battery <NUM> of planar flexible RF tag <NUM> of <FIG>. Charging device <NUM> includes two metal charging plates <NUM>(<NUM>) and <NUM>(<NUM>) that are each electrically coupled to a different output of a variable oscillator <NUM> via one of two inductors <NUM>(<NUM>) and <NUM>(<NUM>). Metal charging plates <NUM> are each of a similar size and shape to a corresponding one of antenna patches <NUM>(<NUM>) and <NUM>(<NUM>). A frequency of variable oscillator <NUM> is controlled by a microcontroller <NUM> based upon a current through inductor <NUM>(<NUM>) that is sensed by a current sensor <NUM>. Since metal charging plates <NUM> and planar complementary patch antenna <NUM> are balanced, current through inductor <NUM>(<NUM>) is assumed to be similar to current through inductor <NUM>(<NUM>) and therefore is not measured. Variable oscillator <NUM> operates at a frequency (e.g., in an unlicensed ISM band - <NUM>) that is much lower than the RF operating frequency of antenna patches <NUM>. Metal charging plates <NUM> are sized and positioned on a dielectric substrate <NUM>.

Charging device <NUM> operates as an external non-electrical contact charger for charging rechargeable battery <NUM> of planar flexible RF tag <NUM>. In one embodiment, metal charging plates <NUM> have identical geometry to antenna patches <NUM> and are printed onto dielectric substrate <NUM> which functions to separate metal charging plates <NUM> from antenna patches <NUM> during charging. Charging device <NUM> has a flat side which is placed in very close proximity and in registration to antenna patches <NUM> to form a set of two "effective" capacitors. The capacitors couple the low frequency RF currents (herein also referred to as capacitive power) from the charging device <NUM> to antenna patches <NUM> within planar flexible RF tag <NUM>. Circuitry of charging device <NUM> includes a matching set of inductors in series with the effective capacitors formed by metal charging plates <NUM>, dielectric substrate <NUM>, and antenna patches <NUM>. The value of these inductors is calculated to be resonant with the effective capacitors at the charging frequency to allow for maximum efficiency for transfer of the maximum power and thereby a lowest time to charge rechargeable battery <NUM> of planar flexible RF tag <NUM>. Microcontroller <NUM> within charging device <NUM> uses current sensor <NUM> to sense the AC RF current draw and adjusts, under closed loop control, the RF frequency of variable oscillator <NUM> to the exact resonance frequency for the effective capacitors.

<FIG> is a top view of the planar flexible RF tag <NUM> of <FIG>, in an embodiment. Planar flexible RF tag <NUM> is shown within a permanently sealed enclosure <NUM> that is for example a permanently sealed, thin flexible plastic packaging that allows for inclusion of planar flexible RF tag <NUM> into pockets of, and/or sewn into, clothing, uniform fabric, and other attire of the individual. For example, enclosure <NUM> may include provision for attachment such as areas for sewing, loops, button holes, and the like. The sealed nature of enclosure <NUM> allows for operation of planar flexible RF tag <NUM> in wet or dirty conditions as well as being amenable to washing. Components of planar flexible RF tag <NUM> are positioned on a flexible substrate <NUM> that is contained by enclosure <NUM>, such that planar flexible RF tag <NUM> is pliable. In one embodiment, antenna patches <NUM> are formed of conductive metal positioned on one side of flexible substrate <NUM>, which is non-electrically-conductive, and antenna patches <NUM> have geometry defining transmission of a wireless UWB signal. The geometry of antenna patches <NUM> is selected to generate the wireless UWB signal with a propagation pattern (e.g., see <FIG>) sufficient for use in a real-time location system. Although shown as rectangular, the geometry of antenna patches <NUM> is selected to obtain the desired propagation pattern and for operation at a desired transmission frequency. <FIG> also shows an orientation reference <NUM> that is relative to the physical embodiment of planar flexible RF tag <NUM>.

<FIG> shows a cross section B-B of the planar flexible RF tag <NUM> of <FIG> and a cross section of the charging device <NUM> of <FIG>, in embodiment. As shown for charging device <NUM>, metal charging plates <NUM> are positioned on dielectric substrate <NUM>, which is for example a circuit board, such that metal charging plates <NUM> align with antenna patches <NUM> of planar flexible RF tag <NUM>.

For planar flexible RF tag <NUM>, antenna patches <NUM> are positioned on a first side of flexible substrate <NUM>, and components <NUM> of decoupling circuits <NUM>, full wave rectifier halves <NUM>, <NUM>, charging regulator circuit <NUM>, microcontroller circuit <NUM>, and RF transceiver circuit <NUM>, and rechargeable battery <NUM> are positioned on a second side, opposite the first side, of flexible substrate <NUM> as shown. Rechargeable battery <NUM> is flat and flexible. In one embodiment, rechargeable battery <NUM> is a thin flexible rechargeable lithium polymer battery from BrightVolt Inc. Flexible substrate <NUM>, antenna patches <NUM>, components <NUM>, and rechargeable battery <NUM> are all contained within enclosure <NUM>. Planar flexible RF tag <NUM> is thus thin and flexible in format allowing it to be used where the hard potted enclosure of conventional RF tags prohibit use.

<FIG> shows, in cross section, the charging device of <FIG> and <FIG> positioned to charge rechargeable battery <NUM> of planar flexible RF tag <NUM> of <FIG>, <FIG>, and <FIG>. Charging device <NUM> is positioned over planar flexible RF tag <NUM> such that metal charging plates <NUM> are aligned with antenna patches <NUM>. Where planar flexible RF tag <NUM> is sewn into clothing, fabric <NUM> of that clothing may be between charging device <NUM> and planar flexible RF tag <NUM>. However, the fabric does not prevent charging device <NUM> from charging rechargeable battery <NUM> of planar flexible RF tag <NUM> since no direct electrical contact is required.

<FIG> shows a propagation pattern <NUM> for the planar flexible RF tag <NUM> of <FIG>, and <FIG>, in embodiments. Orientation of propagation pattern <NUM> is shown relative to orientation reference <NUM> of planar flexible RF tag <NUM>. Propagation pattern <NUM> is suitable for tracking an individual using a real-time location system.

<FIG> is an image showing exemplary layout of the planar complementary patch antenna <NUM> of <FIG>, in one embodiment. In this embodiment, antenna patches <NUM> are each substantially rectangular, equally sized, and aligned along one edge with spacing <NUM> between them. Planar complementary patch antenna <NUM> also include two feed elements <NUM>(<NUM>) and (<NUM>) that electrically connect a different one of antenna patches <NUM> to decoupling circuits <NUM> (not shown in <FIG>) and RF transceiver circuit <NUM> (not shown in <FIG>). In one embodiment, the geometry (e.g., width <NUM> and length <NUM>, spacing <NUM> and substantially rectangular shape) of antenna patches <NUM> is configured such that planar complementary patch antenna <NUM> is resonant at <NUM> and obtains propagation pattern <NUM>. Manipulating the geometry of the antenna elements (i.e., antenna patches <NUM>) of planar complementary patch antenna <NUM> predictably alters shape and range of propagation of radio waves transmitted therefrom. This facilitates design of planar flexible RF tag <NUM> for a particular use.

<FIG> shows exemplary positioning of two planar flexible RF tags <NUM>/<NUM> of <FIG>, and <FIG>, on an American football player <NUM> to illustrate exemplary orientation of the planar flexible RF tags relative to the player, in an embodiment. Tags <NUM>/<NUM> may be configured with clothing and/or equipment of player <NUM>, as described above.

In particular, each planar flexible RF tag <NUM>/<NUM> is oriented (see orientation references <NUM>(<NUM>) and (<NUM>)) such that transmission power in the forward and backward directions (relative to player <NUM>) is greater than the transmission power in the sideways directions. Thus, less of the transmitted energy is absorbed by the player's body, since less power is transmitted in that direction, as compared to a conventional UWB omnidirectional antenna.

<FIG> show player <NUM> of <FIG> on an American football field <NUM> illustrating exemplary propagation of transmissions <NUM>(<NUM>) and <NUM>(<NUM>) from planar flexible RF tags <NUM>(<NUM>)/<NUM>(<NUM>) and <NUM>(<NUM>)/<NUM>(<NUM>), respectively, of player <NUM>. Plays on the American football field are generally up or down the field <NUM>, as opposed to across the field. Thus, players in general are also facing up and down the length of the field. As shown, field <NUM> is surrounded by a plurality of receivers <NUM> (also known as anchors) that are configured to receive transmissions from planar flexible RF tags <NUM>/<NUM>. The receiver locations and received transmissions are used to determine the location of the planar flexible RF tags <NUM>/<NUM> within the operational area that includes field <NUM>. At least three receivers <NUM> are required to receive a particular transmission to enable location of the corresponding planar flexible RF tag <NUM>/<NUM>.

Transmissions <NUM> correspond to propagation pattern <NUM> (i.e., transmission power of tag <NUM>/<NUM>) of <FIG>, and also illustrate exemplary blockage by the body of player <NUM>. Positioning and orientation of planar flexible RF tags <NUM>/<NUM> (i.e., antenna patches <NUM>/<NUM>) determines the shape of transmission <NUM>, and its effectiveness at being received by receivers <NUM>. By configuring antenna patches <NUM>/<NUM> such that more power is transmitted in the player's forward / backward direction (i.e., <NUM> - <NUM> degrees relative to the orientation reference <NUM> of the antenna, less power is absorbed by the player's body. Further, since field <NUM> is longer than it is wide, more receivers <NUM> receive each transmission <NUM>. The advantages of planar flexible RF tags <NUM>/<NUM> may be used to track other players and objects and used with other sports without departing from the scope hereof.

Planar flexible RF tags <NUM>/<NUM> have at least three main advantages over prior art RF tags. First, antenna patches <NUM>(<NUM>) and (<NUM>) have differential input <NUM> that may be driven in a balanced way (differential) allowing direct connection to a balanced drive input and output of RF transceiver circuit <NUM> without a balun device (balanced-to-unbalanced converter). A conventional microstrip patch antenna has a ground plane and one (or more serial or parallel connected) patches that are driven single ended, thereby requiring the use of a balun device when using a transmitter with a balanced/differential input/output (which more transmitting devices are). By including two antennal patches <NUM> within planar complementary patch antenna <NUM>, and directly connecting each of the antenna patches <NUM> to a different connector of the differential output <NUM> of RF transceiver circuit <NUM>, the balun is not required. Although it is known to drive conventional dipole antennae in a balanced way, it is previously unknown to drive a pair of microstrip patch antennae in a complementary manner similar to driving the conventional dipole antennae. Further, since the balun device is not required and not included, its associated loss is also not incurred which improves transceiver performance and range.

Second, placement geometry (e.g., spacing <NUM>) of the two complementary driven antenna patches <NUM> is configured to allow the electromagnetic field interaction and propagation pattern <NUM> to be sufficient for tracking an individual using an UWB real-time location system. For example, planar flexible RF tag <NUM> of <FIG> may be configured to periodically transmit a radio signal that includes identification information, which is received by the UWB real-time location system, which in turn determines a location of the tag based upon triangulation. The propagation pattern (e.g., propagation pattern <NUM> of <FIG>) in this example is biased transverse to the player's shoulder axis giving better gain in the down and up field directions and diminishing gain toward the players neck and sidelines.

Third, the complementary nature of antenna patches <NUM> and the fact that it is a conducting patch lends itself to a second application crucial to the overall design of planar flexible RF tag <NUM>, which is the battery recharging function. Antenna patches <NUM> may be considered as simply metal plates. When another, complementary set of metal plates (e.g., metal charging plates <NUM> of charging device <NUM>) and a suitable dielectric layer (e.g., dielectric substrate <NUM>) is brought within close proximity of the antenna patches <NUM>, as shown in <FIG>, then at frequencies much lower than the microwave operating frequency of antenna patches <NUM>, power is transferred from the metal plates to the antenna patches. For sufficient power transfer from the metal plates to the antenna patches, these metal plates match the geometry (e.g., size, shape, and spacing) of the antenna patches. With suitable decoupling (as provided by decoupling circuits <NUM>), rectification (as provided by full wave rectifier halves <NUM>, <NUM>) and charge management circuits (as provide by charging regulator circuit <NUM>), this power transfer may be used to charge rechargeable battery <NUM> without requiring electrical contact. Thus, enclosure <NUM> need not be breached or opened to recharge rechargeable battery <NUM>.

Advantageously, the non-electrical contact battery recharging may be performed as needed without removal of planar flexible RF tag <NUM> from clothing. Alternatively, as with planar flexible RF tag <NUM>, connector <NUM> is easily accessed to charge rechargeable battery <NUM>.

Since planar flexible RF tag <NUM>/<NUM> is thin (not having 3D antenna or a thick battery), flexible (having components mounted on a flexible substrate and a flexible rechargeable battery) and light weight (the thin efficient operation does not require the use of a single-use higher powered battery), it is much less obtrusive and therefore more widely acceptable for use in tracking athletes and objects in hostile environments.

The thin profile of planar flexible RF tag <NUM>/<NUM> allows it to be placed unobtrusively on or in athletic equipment and on or in athletic clothing. In one embodiment, a lower surface <NUM>/<NUM> of planar flexible RF tag <NUM>/<NUM> has an adhesive coating that allows planar flexible RF tag <NUM>/<NUM> to adhere to a surface (e.g., sports equipment, helmet, clothing, skin of the athlete). In one embodiment, the adhesive is protected by a removable layer that allows planar flexible RF tag <NUM>/<NUM> to be applied using a technique similar to applying a Band-Aid. For example, planar flexible RF tag <NUM>/<NUM> may be attached to a bicycle to allow a real-time location system to track the movement of that bicycle and the rider. In another embodiment, planar flexible RF tag <NUM>/<NUM> is attached to a lanyard and/or worn like a pendant. Thereby, a golfer may wear planar flexible RF tag <NUM>/<NUM> around their neck for example.

In the configuration shown in <FIG>, planar complementary patch antenna <NUM> generates propagation pattern <NUM> which is ideally suited for operation within planar flexible RF tag <NUM> to allow a real-time location system to track athletes performing within a stadium.

As shown in <FIG>, <FIG> rechargeable battery <NUM>/<NUM> is thin and flexible, thereby also allowing planar flexible RF tag <NUM>/<NUM> to be flexible. This alone is a considerable advance in technology for tracking athletes since planar flexible RF tag <NUM>/<NUM>, by being flexible and thin, may thereby provide for easier, less obtrusive placement in athletic equipment and/or clothing.

Antenna patch <NUM> and planar complementary patch antenna <NUM> reduce the overall thickness of planar flexible RF tag <NUM>/<NUM> since the conventionally used 3D antenna design is not required. Further, antenna patch <NUM> and planar complementary patch antenna <NUM> have reduced fragility since there is no 3D structure mounted away from the supporting substrate that requires protection.

Since antenna patch <NUM> and planar complementary patch antenna <NUM> are substantially flat, less protection (as compared to a more delicate 3D structure) is required and they may even be deformed (flexed) without significant loss in performance (e.g., deviation from propagation pattern <NUM> of <FIG>). Thus, unlike prior art RF tags, planar flexible RF tag <NUM>/<NUM> may utilize flexible substrate <NUM>/<NUM> to support each of antenna patch <NUM> and planar complementary patch antenna <NUM>, components <NUM>/<NUM>, and rechargeable battery <NUM>/<NUM>. This flexibility significantly advances the art of RF tracking systems where prior art UWB RF tags were built using rigid circuit boards and required hard, thick housings. In the prior art, these rigid PCBs were required to support and protect the 3D antenna, and to support the larger, heavier and non-flexibly battery.

Historically, UWB tags were designed from discrete components that were interconnected by etched tracked on a printed circuit board. At UWB frequencies absolutely everything, including the etches, effects the performance of the circuit. For this reason, etches need to be considered components of the UWB and so having them flexing, stretching and contracting wreaks havoc with circuit performance. Within planar flexible RF tag <NUM>/<NUM>, UWB components and connectivity may be implemented within an integrated circuit that attaches to flexible substrate <NUM>/<NUM>. Thus, UWB circuitry itself is not susceptible to bending within planar flexible RF tag <NUM>/<NUM>.

Since planar flexible RF tag <NUM>/<NUM> is flexible, when incorporated within athletic equipment, configured within clothing, or attaches directly to an athlete, inevitable bending of planar flexible RF tag <NUM>/<NUM> is accommodated through the flexibility rather than resulting in breakage. Thus, planar flexible RF tag <NUM>/<NUM> is less fragile that prior art RF tags. Thus, this flexibility also makes planar flexible RF tag <NUM>/<NUM> more adaptable to the environment, the athlete, the clothing, and/or the equipment upon which they are mounted on or in.

Although the embodiments described above and shown in the figures have one or two antenna patches, further embodiments are envisioned where multiple antenna patches are coupled together in one or both of serial and parallel configurations.

Claim 1:
A planar flexible radio-frequency, RF, tag (<NUM>) for use in a real-time location system, the planar flexible RF tag comprising:
a flexible substrate (<NUM>);
a planar complementary patch antenna (<NUM>) comprising first and second antenna patches (<NUM>) and a differential input (<NUM>), the first and second antenna patches being positioned on a first side of the flexible substrate;
an RF transmitter circuit positioned on the flexible substrate and having a differential output (<NUM>) electrically coupled to the differential input (<NUM>); and
a microcontroller circuit (<NUM>) positioned on the flexible substrate and electrically coupled to control the RF transmitter circuit to drive the planar complementary patch antenna to transmit a radio signal;
characterized in that it further comprises:
a first decoupling circuit (<NUM>) positioned on the flexible substrate and electrically coupled to the first antenna patch ;
a second decoupling circuit (<NUM>) positioned on the flexible substrate and electrically coupled to the second antenna patch ;
a full-wave rectifier positioned on the flexible substrate and having a first half (<NUM>) electrically coupled to the first decoupling circuit, and a second half (<NUM>) electrically coupled to the second decoupling circuit ; and
a charging regulator circuit (<NUM>) positioned on the flexible substrate and electrically coupled to the full-wave rectifier to receive power, via the first and second antenna patches, from a charging device (<NUM>) that capacitively couples to the first and second antenna patches.