METHOD AND APPARATUS FOR USING SLAP BRACELET AS COMPONENT OF BODY-WORN ANTENNA STRUCTURE

Aspects of the disclosure relate to methods, apparatus, and systems for mitigating signal attenuation at a body-worn device transmitting a radio signal. An antenna structure for the body-worn device includes an antenna array configured to radiate at least one radio signal and a conductive band capacitively coupled to the antenna array. The conductive band is configured to detachably couple to a body of a user, and mitigate attenuation of the at least one radio signal when the conductive band is coupled to the body. The conductive band mitigates the attenuation by facilitating a radio frequency (RF) signal current corresponding to the at least one radio signal to flow through the conductive band and preventing absorption of the RF signal current by the body.

TECHNICAL FIELD

The technology discussed below relates generally to antennas, and more particularly, to body-worn antenna structures.

INTRODUCTION

Advancements in wearable technologies have made it possible to expand the scope and extent of communications capabilities. For example, wrist or body-worn devices are in wide use for purposes of communication. Such devices may be used to track or identify an object or person in a space or to transmit or receive relevant data. However, the close proximity of a wearable device's antenna to a human body makes it difficult to provide efficient and/or effective radiation.

Recent trends have dictated that wearable devices be made as small as possible. For example, combining the small size of a wrist or body-worn device with the increasing demand for better performance presents a number of challenges. Antennas and impedance matching associated with a wearable device must be able to discriminate between a number of signals to obtain a particular signal of interest or to increase the sensitivity/range of the device. An antenna also needs to be an efficient radiator. However, if a device is manufactured in accordance with a smaller form factor, performance may be compromised when using a correspondingly smaller antenna especially, when located in close proximity to the human body. Improvements in creative antenna design and manufacture are needed to accommodate smaller devices.

In previous wrist or body-worn devices, such as a smartwatch, an antenna array may be located solely within a puck portion (main or “watch” portion), or solely within a wristband portion, of a device. However, because of the close proximity of the antenna array to the wrist or body and the body's inherent ability to absorb radio signals, a maximum signal radiation range of such devices is limited (e.g., 1 to 2 meters). Moreover, because the previous wrist or body-worn devices do not allow for tuning of the antenna array, signal absorption by the human body cannot be mitigated, and therefore, the signal radiation range cannot be extended beyond the current limit (e.g., 1 to 2 meters). Accordingly, the present disclosure is directed to providing a structure and/or technique for improving/tuning an antenna array of a wrist or body-worn device in order to extend a maximum signal radiation range of the antenna array.

BRIEF SUMMARY OF SOME EXAMPLES

Aspects of the disclosure relate to methods, apparatus, and systems for mitigating signal attenuation on a body-worn device transmitting a signal. A system includes a body-worn device (e.g., radio frequency identification (RFID) tag) and a reading device (e.g., RFID reader). The body-worn device may include a circuit, an antenna array, and a conductive band capacitively coupled to the antenna array. The conductive band may be detachably coupled to a body of a user of the device. The body-worn device may operate without a battery or internal power source. As such, the body-worn device may receive energy from the reading device's transmission and use that same energy to send back a reply transmission. In an aspect, a construction of the conductive band (e.g., length, width, and/or thickness) may be tuned or adjusted to various sizes to improve radiation performance properties of the antenna array. Other aspects, embodiments, and features are also claimed and described.

In one example, an antenna structure for a body-worn device is disclosed. The antenna structure includes an antenna array configured to radiate at least one radio signal, and a conductive band capacitively coupled to the antenna array. The conductive band is configured to detachably couple to a body of a user and mitigate attenuation of the at least one radio signal when the conductive band is coupled to the body.

In another example, a method of mitigating signal attenuation on a body-worn device is disclosed. The method includes providing, in the body-worn device, an antenna array and a conductive band capacitively coupled to the antenna array, detachably coupling the conductive band to a body of a user, radiating at least one radio signal from the antenna array, and mitigating attenuation of the at least one radio signal via the conductive band when the conductive band is coupled to the body.

In a further example, a body-worn device for transmitting a radio signal is disclosed. The body-worn device includes an antenna array and a circuit configured to receive, via the antenna array, a first signal transmitted from a reading device, generate, based on an energy of the first signal, a second signal specific to the body-worn device, and transmit the second signal to the reading device via the antenna array. The body-worn device further includes a conductive band capacitively coupled to the antenna array, wherein the conductive band is configured to detachably couple to a body of a user, and mitigate attenuation of the second signal when the conductive band is coupled to the body.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appended drawings is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. In some instances, well known structures and components are shown in block diagram form in order to avoid obscuring such concepts. While aspects and embodiments are described in this application by illustration to some examples, those skilled in the art will understand that additional implementations and use cases may come about in many different arrangements and scenarios. Innovations described herein may be implemented across many differing platform types, devices, systems, shapes, sizes, and/or packaging arrangements.

A human body presents a significant challenge to the transmissivity and reflection of radio signals. Due to the inherent amount of salt and water in the human body, a radio signal may be absorbed by the human body and unable to propagate to an intended destination. In order to achieve radio transmission or backscatter within a detectable range, aspects of the disclosure provide an apparatus and method for securely fastening a radio device onto the human body that supports and augments a radio operation.

In an aspect, an apparatus is provided that includes a metal spring band (e.g., steel spring band) which sits beneath a radio device that is capable of operating at different and discrete frequencies. The metal spring band is configured to shield the radio device from a human body on which the apparatus is worn. The metal spring band may be part of an overall antenna structure for the radio device. The metal spring band may or may not be coupled to the radio device to perform an antenna structure function. The radio device may be optimized by utilizing a width, length, and/or thickness of the metal spring band as a tunable variable. In addition, an overall size of the metal spring band may be optimized to improve shielding of the antenna structure from the human body.

In an aspect, although the spring band is described above as a metal spring band (e.g., steel spring band), the spring band is not limited to a metal material alone. It is contemplated that the spring band may be made of other materials, such as a conductive polymer, a metallic mesh, a metal-imbued ceramic, or any other material that can be worn on the human body while having radio frequency (RF) antenna functionality or characteristics.

FIG. 1illustrates a curved (or bent) configuration of an example antenna structure100according to an aspect of the present disclosure.FIG. 2illustrates a flat (or straight) configuration of the example antenna structure100according to an aspect of the present disclosure.

In an aspect, the antenna structure100includes an antenna102and a slap band104that may be electrically coupled to the antenna102. The slap band104is made of a malleable material that will allow the slap band to maintain a desired configuration. For example, as shown inFIG. 1, the slap band104may be curved or bent from a flat configuration so as to wrap around a user's wrist or other body part. The slap band104may also revert back to the flat (or straight) configuration (FIG. 2) from the curved configuration, such as when the slap band104is removed from the user's wrist. Furthermore, the malleable material of the slap band104is conductive so as to electrically couple with the antenna102. For example, the slap band104may be made of steel, conductive polymer, metallic mesh, metal-imbued ceramic, or any other conductive material.

The slap band104may be directly coupled or otherwise coupled to the antenna102. In an aspect, the slap band104includes a ground plane structure wherein radio frequency (RF) current may flow in a conductive portion of the slap band104and around the user's wrist rather than being lost through the band and/or the user's wrist. One or more portions of the antenna102and the slap band104may or may not be electrically coupled together depending on a coupling mechanism used to join the slap band104with the antenna102.

In an aspect, physical dimensions of the slap band104may be varied or tuned. For example, a length, width, and/or thickness of the slap band may be adjusted to various sizes in order to achieve desired performance characteristics at the antenna102. Additionally and/or alternatively, the length, width, and/or thickness of the slap band104may be varied to hide or shield the effects of the human body on the performance of the antenna102.

FIG. 3illustrates the example antenna structure100having an antenna102with connectorized antenna elements according to an aspect of the present disclosure.FIG. 4illustrates the example antenna structure100having an antenna102coupled to a slap band104via one or more capacitive couplings402according to an aspect of the present disclosure.

In an aspect, the antenna102of the antenna structure100may be constructed on a slab of dielectric material, which aids in miniaturization of the antenna102. In one aspect, air may be used as the dielectric material. As shown inFIG. 3, the antenna102may include a first antenna element (e.g., first printed circuit board (PCB))302, a second antenna element (e.g., second PCB)304, and an air gap306between the first antenna element302and the second antenna element304. The first antenna element302is connectorized to the second antenna element304(e.g., via one or more cables or wires308) above the slap band104in order to achieve a necessary radiating structure. The slap band104may act as a ground plane. In some aspects, the antenna102may use other materials (e.g., ceramic) with differing dielectric properties to aid in antenna miniaturization.

In an aspect, the antenna structure100is different from previous types of body-worn devices (e.g., smartwatches). For example, in a previous type of body-worn device, an antenna structure is solely built into a main portion or body of the device itself. Thus, the smartwatch' s band does not affect an antenna structure function. In contrast, in the present disclosure, the slap band104is part of the antenna structure100, and therefore, affects a function of the antenna structure100. Whether the slap band104is electrically connected to or disparate from the antenna102, a dielectric value of the slap band104is used in combination with the antenna102to affect/extend a signal radiation range of the antenna structure100. In an aspect, a length, width, and/or thickness of the slap band104may be tuned to a specific size to achieve a desired radiation range. Previously, the antenna102may have had a maximum signal radiation range of 1 to 2 meters. However, by using the tuned slap band104as part of the antenna structure100, a body-worn device implementing the antenna structure100may be able to achieve a maximum signal radiation range of 4 to 8 meters. Thus, use of the slap band104allows the antenna structure100to have an extended range while being worn on the body.

FIG. 5is an example diagram500of the antenna structure100(including the antenna102and the slap band104) wrapped around a wrist (or other body part)502of a user. InFIG. 5, a surface current in the slap band104is plotted to show how the slap band104is acting as part of a radiating structure of the antenna102.FIG. 6is another example diagram600of the antenna structure100wrapped around the wrist (or other body part)502of the user. InFIG. 6, an electric field in the slap band104is plotted to show how the slap band104is acting as part of the radiating structure of the antenna102.FIG. 7is a diagram700illustrating an example radiation pattern702of the antenna102.

In an aspect, a performance of the antenna102may be hindered when in close proximity to the human body. As such, the slap band104(made of a conductive material) may be used to shield the antenna102from the negative effects of the human body. Moreover, the slap band104may be used as part of the radiating structure of the antenna102such that RF current may flow through the slap band104. As such, the RF current may be directed to flow around the user's wrist/body instead of through the user, thus avoiding potential loss. Performance characteristics of the antenna102may be adjusted or improved by controlling a configuration of the slap band104in conjunction with modifications to the antenna102.

In an aspect, various performance characteristics of the antenna102may be controlled based on a modification to the slap band104acting as a ground plane, or a modification to an armature associated with a ground plane of the antenna102. The performance characteristics may include but are not limited to antenna size, frequency, gain, radiation pattern, radiation efficiency, aperture, and/or impedance. In some aspects, the performance characteristics may be controlled via a modification of the structure of the antenna102, a modification of the structure of the slap band104, or a combination of both. In an aspect, the performance of the antenna102when the slap band104is in the curved/bent configuration may be designed to be different from the performance of the antenna102when the slap band104is in the flat/straight configuration. For example, a radiation pattern of the antenna102may be adjusted as desired by shifting from a curved/bent band configuration to a flat/straight band configuration or vice versa, thus facilitating two different use cases at an end device.

In an aspect, the antenna structure100may include multiple antennas. The antennas may be active sequentially or simultaneously with one another. Moreover, the slap band104may be shared among the multiple antennas so that the slap band104may be used as part of a radiating structure of each antenna. In an aspect, the antenna structure100may include physical elements configured to adjust a position, size, and or polarization of an antenna in order to direct antenna signals in a more accurate and/or efficient manner. In one example of the antenna structure100including multiple antennas, the antenna structure may include a near-field communication (NFC) coil and an ultra-high frequency (UHF) antenna located in close proximity to one another. The NFC coil and UHF antenna may share the slap band104as part of their radiating structures so as to allow for the miniaturization of the co-located antennas (NFC coil and UHF antenna) in close physical proximity.

FIG. 8is a plot800of an example radiation pattern of an antenna102with a slap band104when simulated on a wrist502of a user.FIG. 9is a Smith chart900depicting an example S(1,1) performance of an antenna102with a slap band104when simulated on a wrist502of a user.FIG. 10is an example gain plot1000depicting gain versus frequency (e.g., 0.915 GHz) of an antenna structure100for different angles theta (degrees).

In an aspect, the antenna structure100may include directors or reflectors that can be dynamically adjusted (or reconfigured) to shape a radiation pattern or other desired antenna characteristics of an antenna. For example, the slap band104may be considered a director/reflector that may be reconfigured to shape a radiation pattern or other characteristic of the antenna102. Activating or deactivating a director/reflector with a switch or other non-direct coupling mechanism may adjust RF characteristics of the antenna structure100as desired. The switch may be a physical semiconductor-based switch or may be some hardware element capable of altering a capacitive coupling of the slap band104to the antenna102.

FIG. 11is a block diagram illustrating an example system1100for communicating radio signals between devices according to an aspect of the present disclosure. The system1100includes a body-worn device1102(e.g., radio frequency identification (RFID) tag) and a reading device1110(e.g., RFID reader). The body-worn device1102may include a circuit1104, an antenna array1106, and a conductive band1108capacitively coupled to the antenna array1106. The conductive band1108may be detachably coupled to a body of a user of the device1102. Moreover, a combination of the antenna array1106and the conductive band1108may be referred to as the “antenna structure” mentioned throughout this disclosure.

In an aspect, the body-worn device1102may operate without a battery or internal power source. As such, the body-worn device1102may receive energy from the reading device's transmission1112and use that same energy to send back a reply transmission1114. For example, the body-worn device1102receives, via the antenna array1106, electromagnetic waves1112propagated from the reading device1110. Once the waves1112reach the antenna array1106, energy of the waves1112travels through the antenna array1106to activate the circuit1104. The circuit1104modulates the energy with information specific to the body-worn device1102(e.g., modulated with the circuit's data) to generate the reply transmission1114. The circuit1104then transmits the reply transmission1114(modulated with the information specific to the body-worn device1102/circuit1104) to the reading device1110via the antenna array1106in the form of electromagnetic waves.

The reading device1110may receive the reply transmission1114, read the information specific to the body-worn device1102/circuit1104, and perform an operation corresponding to the body-worn device1102based on the information. For example, the reading device1110may account for the presence of the user wearing the body-worn device1102within a vicinity of the reading device1110and/or grant the user wearing the body-worn device1102pre-determined services corresponding to the information (e.g., within a theme park environment).

In an aspect, the conductive band1108may mitigate attenuation of the reply transmission1114when the conductive band1108is coupled to the body of the user. For example, when the circuit1104transmits the reply transmission1114to the reading device1110via the antenna array1106, the conductive band1108may facilitate a radio frequency (RF) signal current corresponding to the reply transmission1114to flow through the conductive band1108and prevent absorption of the RF signal current by the body.

Previous body-worn devices (e.g., previous wristband tags/systems) may suffer from a limited signal radiation range because of the human body's ability to absorb certain signal frequencies (e.g., 900 MHz). Typically, a maximum range for such devices is approximately 1 to 2 meters. Accordingly, for certain applications, such as applications implemented during large gatherings (e.g., music festivals, sporting events, etc.), use of the previous body-worn devices may be cumbersome. For example, due to the limited signal radiation range of a device caused by the proximity of a user's wrist to an antenna structure (i.e., the user's wrist attenuates most of the device signal emitted from the antenna structure), it may be necessary to erect reading portals near the user in order to read a short range transmission from the user's device.

Aspects of the present disclosure provide a system and/or method for enabling a reading device (e.g., RFID reader) to read signals from a body-worn device as far as 4 to 8 meters away. As such, a distance at which the body-worn device can be read by the reading device may be defined. In an aspect, the present disclosure provides a body-worn device configured to mitigate signal attenuation caused by the body (e.g., wrist) of the user. In a further aspect, antenna structure properties may be tuned to define a maximum distance at which a reading device can detect signals from the antenna structure of the body-worn device, while allowing a form factor of the body-worn device to fit most users. Thus, not only does the body-worn device of the present disclosure function to have a tunable antenna parameter to achieve a desired signal range, but the body-worn device also conforms to a size/shape of the user.

FIG. 12is a flow chart illustrating an exemplary process1200for mitigating signal attenuation on a body-worn device according to an aspect of the present disclosure. In some examples, the process1200may be carried out by the body-worn device1102or any suitable apparatus or means for carrying out the functions or algorithm described below.

At1202, an antenna array (e.g., antenna102or antenna array1106) and a conductive band (e.g., slap band104or conductive band1108) capacitively coupled to the antenna array is provided in the body-worn device. In an aspect, the conductive band may be made of steel, conductive polymer, metallic mesh, and/or metal-imbued ceramic.

In an aspect, providing the conductive band in the body-worn device may include configuring a length, a width, and/or a thickness of the conductive band to optimize one or more performance characteristics of the antenna array. For example, optimizing a performance characteristic may include extending a maximum signal radiation range of the antenna array (e.g., to a range of 4 to 8 meters), such that a reading device will be able to read a transmission from the body-worn device from such range. In another aspect, providing the conductive band in the body-worn device may include configuring a length, a width, and/or a thickness of the conductive band to shield an absorption effect of the body on at least one radio signal radiated from the antenna array.

At1204, the conductive band is detachably coupled to a body of a user. In an aspect, the conductive band is detachably coupled to the body of the user by flattening the conductive band to a substantially straight configuration to uncouple the conductive band from the body and bending the conductive band to a curved configuration to couple the conductive band to the body. In an aspect, a performance characteristic of the antenna array (e.g., radiation pattern) when the conductive band is in the straight configuration may be different from a performance characteristic of the antenna array when the conductive band is in the curved configuration.

At1206, at least one radio signal (e.g., reply transmission1114) is radiated from the antenna array. In an aspect, the at least one radio signal has a frequency in an ultra-high frequency (UHF) range (e.g., approximately 900 MHz), or any other frequency susceptible to being absorbed by the body.

At1208, attenuation of the at least one radio signal is mitigated via the conductive band when the conductive band is coupled to the body. In an aspect, the attenuation is mitigated by facilitating a radio frequency (RF) signal current corresponding to the at least one radio signal to flow through the conductive band, and preventing absorption of the RF signal current by the body.