PATENT DOCUMENT

Publication Number: US-8797146-B2
Application Number: US-201113092586-A
Country: US
Kind Code: B2

Title: Autonomous battery-free microwave frequency communication system

Abstract:
An autonomous battery-free microwave frequency communication device which includes a capacitance, at least one antenna, a microwave energy harvesting system, a microwave frequency transceiver, and a control system. The energy harvesting system is configured to harvest and store microwave energy received via the antenna onto the capacitance. The transceiver is empowered by energy stored on the capacitance, and is configured to autonomously generate a microwave frequency carrier and to autonomously transmit information using the microwave frequency carrier according to a predetermined communications protocol via the antenna. The control system is empowered by energy stored on the capacitance, and is configured to provide information for transmission. Energy may be harvested from various communication forms, such as wireless network protocols or cellular communications. The frequency band from which energy is harvested may differ from the frequency band used for communications. The energy storage enables autonomous communications with external devices according to common or standard wireless communication protocols.

Claims:
What is claimed is: 
     
       1. An autonomous battery-free microwave frequency communication device, comprising:
 a capacitor; 
 at least one antenna; 
 a microwave energy harvesting system which is configured to harvest microwave energy from charging packets received via said at least one antenna and configured to store the microwave energy on said capacitor, wherein the microwave energy harvesting system is configured to transmit a response packet in response to determining that the capacitor is sufficiently charged; 
 a microwave frequency transceiver powered by energy stored on said capacitor, which is configured to use a portion of energy stored on said capacitor to autonomously generate a microwave frequency carrier and to autonomously transmit information using said microwave frequency carrier according to a predetermined communications protocol via said at least one antenna; and 
 a control system powered by energy stored on said capacitor, which is configured to provide said information for transmission, wherein the charging packets comprise wireless local area network (WLAN) protocol beacon frames that are selectively generated for charging the capacitor. 
 
     
     
       2. The autonomous battery-free microwave frequency communication device of  claim 1 , wherein said microwave energy harvesting system is configured to detect and convert microwave energy comprising a communication packet transmitted by an external device and received by said at least one antenna. 
     
     
       3. The autonomous battery-free microwave frequency communication device of  claim 1 , wherein said microwave energy received via said at least one antenna comprises microwave energy in a first microwave frequency band, and wherein said microwave frequency transceiver is configured to transmit information according to said predetermined communications protocol in a second microwave frequency band which is different from said first microwave frequency band. 
     
     
       4. The autonomous battery-free microwave frequency communication device of  claim 1 , wherein said at least one antenna comprises at least one common antenna which is coupled to and used by both said microwave energy harvesting system and said microwave frequency transceiver. 
     
     
       5. The autonomous battery-free microwave frequency communication device of  claim 1 , wherein said at least one antenna comprises at least one first antenna coupled to said microwave energy harvesting system for energy harvesting and at least one second antenna coupled to said microwave frequency transceiver for communications. 
     
     
       6. The autonomous battery-free microwave frequency communication device of  claim 1 , wherein said microwave frequency transceiver comprises:
 a frame generation circuit configured to generate a data frame formatted according to said predetermined communications protocol using energy stored on said capacitor; 
 a microwave frequency carrier generation circuit configured to generate said microwave frequency carrier according to said predetermined communications protocol using energy stored on said capacitor; 
 a modulator circuit configured to modulate said data frame on said microwave frequency carrier according to said predetermined communications protocol using energy stored on said capacitor to provide modulation information; and 
 a transmitter circuit configured to transmit said modulation information via said at least one antenna according to said predetermined communications protocol using energy stored on said capacitor. 
 
     
     
       7. The autonomous battery-free microwave frequency communication device of  claim 1 , wherein said microwave frequency transceiver comprises:
 a receiver circuit configured to receive modulated information via said at least one antenna according to said predetermined communications protocol using energy stored on said capacitor; 
 a microwave frequency carrier generation circuit configured to generate said microwave frequency carrier according to said predetermined communications protocol using energy stored on said capacitor; 
 a demodulator circuit configured to demodulate said received modulated information using said microwave frequency carrier according to said predetermined communications protocol using energy stored on said capacitor to provide a received data frame; and 
 a frame processing circuit configured to process said received data frame formatted according to said predetermined communications protocol using energy stored on said capacitor. 
 
     
     
       8. The autonomous battery-free microwave frequency communication device of  claim 1 , wherein said predetermined communications protocol comprises either one of a Wi-Fi communications protocol and a Bluetooth communications protocol. 
     
     
       9. The autonomous battery-free microwave frequency communication device of  claim 1 , wherein said control system comprises:
 a controller configured to processes information received by said microwave frequency transceiver and to generate information to be transmitted by said microwave frequency transceiver; and 
 a non-volatile memory coupled to said controller. 
 
     
     
       10. The autonomous battery-free microwave frequency communication device of  claim 1 , wherein said microwave energy harvesting system transfers and stores microwave energy received via said at least one antenna onto said capacitor during a first time period, and wherein said microwave frequency transceiver autonomously transmits information during a second time period which is mutually exclusive relative to said first time period. 
     
     
       11. The autonomous battery-free microwave communication device defined in  claim 1 , wherein the charging packets are formatted to prevent interoperability with other microwave frequency communication devices. 
     
     
       12. The autonomous battery-free microwave communication device defined in  claim 1 , wherein the response packet comprises a probe request packet. 
     
     
       13. A method of performing autonomous communications by a battery-free device comprising:
 receiving charging packets that comprise wireless local area network (WLAN) clear to send (CTS) packets via at least one antenna; 
 harvesting microwave energy from the received wireless local area network (WLAN) clear to send (CTS) packets and storing the harvested microwave energy on a capacitor, wherein the wireless local area network (WLAN) clear to send (CTS) packets are selectively generated for charging the capacitor; 
 transmitting a response packet using the at least one antenna in response to determining that the capacitor is sufficiently charged; 
 generating at least one data frame formatted according to a first communications protocol using energy stored on the capacitor; 
 generating a microwave frequency carrier using energy stored on the capacitor; 
 modulating the microwave frequency carrier with the data frame using energy stored on the capacitor to provide a modulated information; and 
 transmitting the modulated information via the at least one antenna using energy stored on the capacitor. 
 
     
     
       14. The method of  claim 13 , wherein said receiving microwave energy comprises receiving microwave energy on a plurality of directional antennas. 
     
     
       15. The method of  claim 13 , wherein said receiving microwave energy comprises receiving the microwave energy on at least one first antenna provided for energy harvesting, and wherein said transmitting the modulated information comprises transmitting the modulated information on at least one second antenna provided for communications. 
     
     
       16. The method of  claim 13 , further comprising:
 said receiving microwave energy comprising receiving at least one microwave modulated data frame; 
 demodulating the microwave modulated data frames using the microwave frequency carrier and using energy stored on the capacitor to provide at least one received data frame; and 
 processing the at least one received data frame according to the first communications protocol to retrieve transmitted information using energy stored on the capacitor. 
 
     
     
       17. The method of  claim 13 , wherein said receiving microwave energy comprises receiving microwave communications in a first microwave frequency band, and wherein said transmitting the modulated information comprises transmitting the modulated information in a second microwave frequency band which is different from the first microwave frequency band. 
     
     
       18. The method of  claim 13 , wherein said receiving microwave energy, harvesting the received microwave energy and storing harvested energy comprises receiving microwave energy, harvesting the received microwave energy and storing harvested energy during a first time period, and wherein said transmitting the modulated information comprises transmitting the modulated information during a second time period which is mutually exclusive relative to the first time period. 
     
     
       19. The method of  claim 13 , further comprising:
 said receiving microwave energy comprising receiving microwave modulated data frames; and 
 processing the microwave modulated data frames to retrieve demodulated data using energy stored on the capacitor. 
 
     
     
       20. The method of  claim 19 , further comprising using the demodulated data to generate at least a portion of a modulated data sequence. 
     
     
       21. A wireless radio frequency tag device, comprising:
 a physical article configured for a predetermined purpose; and 
 an autonomous battery-free microwave frequency communication device embedded on said physical article to enhance said predetermined purpose comprising:
 a capacitor; 
 at least one antenna; 
 a microwave energy harvesting system which is configured to harvest and store microwave energy from wireless local area network (WLAN) request to send (RTS) packets that are selectively generated to charge the capacitor received via said at least one antenna onto said capacitor; 
 a microwave frequency transceiver powered by energy stored on said capacitor, which is configured to use a portion of energy stored on said capacitor to autonomously generate a microwave frequency carrier and to autonomously transmit information using said microwave frequency carrier according to a predetermined communications protocol via said at least one antenna; and 
 a control system powered by energy stored on said capacitor, which is configured to provide said information for transmission, wherein said information is associated with said predetermined purpose, and wherein said control system comprises a memory for storing data associated with said predetermined purpose, wherein said physical article comprises an advertisement flyer and wherein said information and data is associated with at least one commercial enterprise.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application Ser. No. 61/328,291, filed on Apr. 27, 2010 which is hereby incorporated by reference in it entirety for all intents and purposes. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to communications systems, and more particularly to an autonomous battery-free microwave frequency communication device. 
     2. Description of the Related Art 
     A conventional battery-free contact-less wireless communication device is known which is based upon the ISO/IEC (International Organization for Standardization/International Electrotechnical Commission) 14443 near-field communication specification, which uses a relatively-low carrier frequency of 13.56 megaHertz (MHz) and relatively-low data rates of up to 848 kilobits per second (kbps) and involves a battery-powered reader referred to as a “Proximity Coupled Device” or PCD and a battery-free, energy-harvesting “tag” referred to as a “Proximity Integrated Circuit Card” or PICC. The power used to transmit the data read/write requests from the PCD to the PICC is inductively coupled from PCD to PICC at a range of approximately 20 centimeters (cm) or less which is within the “near field” of the PCD. The PICC communicates responses to the PCD by modulating a load according to backscatter communications. In accordance with backscatter communications, there is no active modulation of a signal transmitted from PICC to PCD, there is no generation of an independent carrier by the PICC transmitter, and the PICC must be in the near field of the PCD. The near field is necessary to establish magnetic coupling in which communication is based on induced current. These systems commonly have a simple integrated state machine and associated memory and are currently used in some contact-less credit and debit cards as well as identification cards. 
     Certain standards that cover near-field communications (NFC) with passive tags include, but are not limited to, ISO/IEC 14443 and 15693 (13.56 MHz carrier frequency), ISO/IEC 18000 (135 kiloHertz (kHz), 13.56 MHz, 2.45 gigaHertz (GHz), 860-960 MHz, and 433 MHz), ISO/IEC 18092 and 21481. ISO 18000-4, in particular, uses the 2.4-2.5 GHz band and has an option for microwave-frequency communication with a passive tag using backscattering. 
       FIG. 1  is a figurative and schematic diagram illustrating a conventional Radio Frequency Identification (RFID) near-field communication system  100  with an active RFID reader  101  and a passive RFID tag  103  that responds to the active RFID reader  101  via backscattering, very much like a radar illuminating a target. The active RFID reader  101  includes a magnetic loop antenna  105  which is placed in close proximity with a magnetic loop antenna  107  of the passive RFID tag  103  to establish a magnetic field  106 . The passive RFID tag  103  further includes a shunt capacitance C TUNE , a switch SW, a full-wave rectifier  109  and a storage capacitor C S  coupled to the magnetic loop antenna  107 , in which C S  develops a supply voltage VS for providing power to an RFID tag integrated circuit (IC)  111 . The switch SW includes a series resistance R SW  (which may or may not be a separate physical resistor, but may instead represent the series resistance of the switch SW). The RFID tag IC  111  is shown including a receive (RX) detector  113 , control logic  115 , transmit (TX) switch control  117  and memory  119 . 
     In this RFID system, the active RFID reader  101  operates as an interrogator which develops the magnetic field  106  to provide power and which further modulates the magnetic field  106  to enable communication with tags that are within their range, such as the passive RFID tag  103 . When the active RFID reader  101  is placed in close proximity with the passive RFID tag  103 , the magnetic loop antenna  107  develops inductive current which is converted to voltage across CS for providing power to the RF tag IC  111 . The active RFID reader  101  further modulates the magnetic field  106  to send data, which is detected by the RX detector  113 . Such modulation may be according to any suitable form, such as amplitude modulation (AM) (e.g., on-off key AM), frequency modulation (FM) or phase modulation (PM). The control logic  115  retrieves the data and may provide a response by controlling the switch SW via the TX switch control  117 . During the time that the passive RFID tag  103  communicates back to the active RFID reader  101 , the active RFID reader  101  broadcasts a steady radio frequency (RF) power level via the magnetic field  106 , and the passive RFID tag  103  modulates the impedance of its RF load attached to the magnetic loop antenna  107  by adjusting its reflectivity by controlling the switch SW coupled with other passive components, such as C TUNE . The active RFID reader  101  then receives the data back from the passive RFID tag  103  as a variation in reflection of its transmitted power. 
     In this system, the passive RFID tag  103  can only send data to the nearby interrogator/reader, e.g., the active RFID reader  101 , and the active RFID reader  101  sends data (by induced current) to the passive RFID tag  103 . The passive RFID tag  103  sends data back to the active RFID reader  101  only while it broadcasts energy (e.g., while sending an un-modulated carrier signal via the magnetic field  106 ). The passive RFID tag  103  does not store energy for later use, and it does not generate its own RF carrier. Furthermore, the magnetic loop antennas  105  and  107  are typically rather large and are not commonly available for many types of devices, such as cellular phones or smart phones and the like. The active RFID reader  101 , for example, is typically a tablet or hand scanner or the like particularly configured for RFID tag communications. 
     The conventional RFID tag communication systems, such as the communication system  100 , have several disadvantages. The disadvantages include, for example, the need to have a relatively-large antenna to obtain sufficient energy-harvesting efficiency for the low carrier frequency (long wavelength of over 22 meters) and the lack of available reader interfaces in common devices like mobile phones and portable computers and the like. The conventional RFID tag communication systems operate in lower frequency ranges, such as tens of MHz, and operate at relatively low data rates, such as less than 1 megabit per second (Mbps). 
     Other systems, e.g., using 902-928 MHz for ultra high frequency (UHF) RFID harvest energy but also use backscatter communications. One potential advantage of such devices is that they operate using microwave frequencies. As used herein, microwave frequencies are within the range of about 300 MHz to about 300 GHz. Microwave frequency communications enable the use of relatively small antennas (&lt;2 cm on a side) for increased energy-harvesting efficiency. The disadvantage of 902-928 MHz UHF systems, however, is that they also are not integrated into common devices like mobile phones and portable computers and the like. The common devices typically use Bluetooth or WiFi (802.11) technology, which are already integrated into cellular telephone handsets. 
     It is desired to provide RFID-type communications using battery-free passive tags that are able to communicate with common devices, such as those which operate using standard microwave frequency communications (e.g., Wi-Fi, Bluetooth, etc.). 
     SUMMARY OF THE INVENTION 
     An autonomous battery-free microwave frequency communication device according to one embodiment includes a capacitance, at least one antenna, a microwave energy harvesting system, a microwave frequency transceiver, and a control system. The microwave energy harvesting system is configured to harvest and store microwave energy received via the antenna onto the capacitance. The microwave frequency transceiver is empowered by energy stored on the capacitance, and is configured to autonomously generate a microwave frequency carrier and to autonomously transmit information using the microwave frequency carrier according to a predetermined communications protocol via the antenna. The control system is empowered by energy stored on the capacitance, and is configured to provide information for transmission. 
     A method of performing autonomous communications by a battery-free device according to one embodiment includes receiving microwave energy via at least one antenna, harvesting the received microwave energy and storing harvested energy on a storage capacitance, generating at least one data frame formatted according to a first communications protocol using energy stored on the storage capacitance, generating a microwave frequency carrier using energy stored on the storage capacitance, modulating the microwave frequency carrier with the data frame using energy stored on the storage capacitance to provide a modulated information, and transmitting the modulated information via the at least one antenna using energy stored on the storage capacitance. 
     A wireless radio frequency tag device according to one embodiment includes a physical article configured for a predetermined purpose, and an autonomous battery-free microwave frequency communication device according to embodiments of the present invention and embedded on the physical article to enhance the predetermined purpose. The physical article may take on any of many different types of formats, such as wristbands, advertisement flyers, cards, etc. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The benefits, features, and advantages of the present invention will become better understood with regard to the following description, and accompanying drawings where: 
         FIG. 1  is a figurative and schematic diagram illustrating a conventional Radio Frequency Identification (RFID) near-field communication system with an active RFID reader and a passive RFID tag that responds to the active RFID reader using backscattering communications; 
         FIG. 2  is a block diagram of an autonomous battery-free microwave frequency RF tag according to one embodiment of the present invention; 
         FIG. 3  is a block diagram of a communication system according to one embodiment of the present invention including the battery-free microwave frequency RF tag of  FIG. 2  communicatively coupled with a battery powered device via bi-directional communication link; 
         FIG. 4  is a block diagram of a communication system according to one embodiment of the present invention including the battery-free microwave frequency RF tag of  FIG. 2  communicatively coupled with the device of  FIG. 3  via a bi-directional communication link, which further includes an energy transfer link for transfer of energy from the powered device to the battery free tag device; 
         FIG. 5  is a block diagram showing a wireless disposable wristband incorporating a battery-free microwave frequency RF tag (configured according to any of the embodiments of the tag described herein) which communicates with the device of  FIG. 3  using microwave frequency communications according to one embodiment; 
         FIG. 6  is a block diagram shows a wireless advertisement or flyer (AD/FLYER) incorporating a battery-free microwave frequency RF tag (configured according to any of the embodiments of the tag described herein) which communicates with the device of  FIG. 3  using microwave frequency communications according to one embodiment; 
         FIG. 7  is a block diagram shows a wireless credit, debit, and/or loyalty card incorporating a battery-free microwave frequency RF tag (configured according to any of the embodiments of the tag described herein) which communicates with the device of  FIG. 3  using microwave frequency communications according to one embodiment; 
         FIG. 8  is a figurative diagram showing a portion or fragment of a basic protocol for charging a battery-free microwave frequency RF tag and an initial response sent by the tag for initialization of communications according to one embodiment; 
         FIG. 9  is a figurative diagram showing a fragment of the 802.11 WLAN protocol, in which charging a battery-free microwave frequency RF tag is accomplished by beaconing according to one embodiment; 
         FIG. 10  is a block diagram of an exemplary microwave energy harvesting and storage network implemented according to an embodiment of the present invention; 
         FIGS. 11 and 12  illustrate various conventional circuits which may be used to implement portions of the exemplary microwave energy harvesting and storage network of  FIG. 10 ; and 
         FIG. 13  is a schematic and block diagram of a microwave frequency radio transceiver which may be used to implement the microwave frequency transceiver of the tag of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
     The following description is presented to enable one of ordinary skill in the art to make and use the present invention as provided within the context of a particular application and its requirements. Various modifications to the preferred embodiment will, however, be apparent to one skilled in the art, and the general principles defined herein may be applied to other embodiments. Therefore, the present invention is not intended to be limited to the particular embodiments shown and described herein, but is to be accorded the widest scope consistent with the principles and novel features herein disclosed. 
     Various embodiments disclosed herein incorporate a microwave frequency energy harvesting system coupled to one or more antenna(s) tuned to a range of frequencies and a microwave-frequency transceiver for communications in a network of two or more devices. Energy harvesting may occur when the receiving antenna(s) on the battery-free device is (are) in the far field, the near field, or between the near and far fields of the transmitting antenna(s) in the device providing energy. The same or a different antenna or set of antennas is used for communications. A different set of antennas may be used either to achieve additional gain from directive reception for energy harvesting while simultaneously allowing omni-directional transmission of data from the battery-free device to the device providing energy and possibly other devices or to enable different frequency bands to be used for powering the battery-free device and communicating with the battery-free device. 
     In one set of embodiments, the battery-free device may implement an IEEE (Institute of Electrical and Electronics Engineers) 802.11-compliant radio with an active power amplifier in the 2.4-2.5 GHz band and also implement an energy-harvesting system that draws power from the received 802.11 signal and is tuned to the 2.4-2.5 GHz band. In various embodiments, the battery-free device generates its own microwave frequency carrier signal using dedicated internal circuitry, such as phase-locked loops (PLLs), mixers, and reference frequency oscillators. Various embodiments of this device may use multiple antennas with directional reception to collect a larger amount of received power from the 802.11 transmissions, each directional antenna coupled to one or more energy-harvesting circuit(s). 
     In another set of embodiments, the battery-free device may implement a Bluetooth compliant or Wi-Fi compliant radio in the 2.4-2.5 GHz band (Wi-Fi or Bluetooth) or 4.9-6.0 GHz band (Wi-Fi) and may also implement one or more energy-harvesting circuits(s) tuned to one or more of the cellular telephony uplink transmission bands. Other combinations using one or more frequency bands and energy-harvesting circuits are envisioned. Wi-Fi is a trademark of the Wi-Fi Alliance, which includes various wireless local area network (WLAN) protocols based on the IEEE 802.11 standard along with other wireless communication protocols as known to those of ordinary skill in the art. Bluetooth is a wireless technology based on an industry group specification typically used for exchanging data over relatively short distances. 
     Various embodiments disclosed herein may integrate the microwave frequency battery-free device with a controller subsystem and memory to store various content. The controller subsystem may include finite-state machines, microcontrollers, microprocessors, bus interfaces, and/or peripheral circuitry. Memory may include non-volatile and/or volatile memory and may be one-time and/or many-time programmable. 
     Various embodiments disclosed herein may incorporate passive networks for boosting the voltage received from the antenna(s) in order to more effectively activate subsequent voltage rectifier circuits which may otherwise not be capable of capturing substantial power. 
     Various embodiments disclosed herein also incorporate the microwave frequency battery-free device in a network involving a communication device that also provides energy to the battery-free device and a further communication link from the device providing energy to the battery-free device to a wireless access point or base station that provides a further connection to servers on an intranet or the larger Internet. An intranet in this description may be a corporate or hospital network hosted in a building or through distributed data centers or a network including Virtual Private Network (VPN) links. Examples are included showing usages of the autonomous battery-free microwave-frequency radio device in a network possibly including wireless access points or cellular base stations and servers in an intranet or the larger Internet. The server(s) receive(s) data from the phone or other device that connects to the battery-free device and provides it energy; these data may include processed information from the battery-free device. The server(s) may send responses to the processed information back to the phone or other device connected to the battery-free device. 
       FIG. 2  is a block diagram of an autonomous battery-free microwave frequency RF tag  200  according to one embodiment of the present invention. The tag  200  includes a microwave frequency antenna  201  coupled to a microwave frequency transceiver  203 . The microwave frequency transceiver  203  is further coupled via a host bus  205  to a controller  207 . The controller may be configured in any suitable manner, such as a microprocessor or other type of processor, a programmable state machine or the like, a hard-coded state machine or the like, etc. The controller  207  is coupled to a memory  209 . The microwave frequency transceiver  203  is also shown coupled to an energy harvesting system  211 , which stores energy on at least one energy storage capacitor C 1 . Additional storage capacitors may be included. As shown, for example, N storage capacitors C 1 -CN are shown coupled to the energy harvesting system  211  (in which N is any positive integer including zero). The energy harvesting system  211  may include one or more separate energy harvesting circuits. The energy harvesting system  211  develops a regulated supply voltage VDD, which is provided to other components in the tag  200 , such as the microwave frequency transceiver  203 , the controller  203 , and the memory  209 . 
     The memory  209  includes non-volatile memory  213 . The non-volatile memory  213  is desired to preserve information when the tag  200  has exhausted its stored energy supply provided by charge on the one or more capacitors C 1 -CN. Additionally, the memory  209  may include volatile memory, such as random access memory (RAM)  215  or the like (shown in dashed lines). In certain configurations the RAM  215  may be omitted as consuming significant energy. 
     In one embodiment, the tag  200  is a single antenna system in which the microwave antenna  201  is used for both energy harvesting by the energy harvesting system  211  and communications by the microwave frequency transceiver  203 . In another embodiment, one or more additional microwave antennas, such as shown at  204 , may be included and coupled to the microwave frequency transceiver  203 . In this case the multiple antennas are shared between the microwave frequency transceiver  203  and the energy harvesting system  211 . In yet another embodiment, one or more additional microwave antennas, such as shown at  206 , may be included and coupled to the energy harvesting system  211 . In this case, the one or more antennas coupled to the microwave frequency transceiver  203  are used for data communications, and the one or more antennas coupled to the energy harvesting system  211  are used for energy harvesting and storage. 
     The energy harvesting system  211  is coupled either to the same antenna(s) used by the microwave frequency transceiver  203  or to separate antennas. Separate antennas may be preferable in the case that the tag  200  is configured to communicate with far-away devices that may be placed in arbitrary positions with respect to the tag  200 . In this case, the long-distance path may prefer the use of omni-directional antennas, while the energy harvesting system  211  prefers strongly directional antennas to pick up a maximum amount of power from a nearby transceiver that may be oriented in a particular manner. One or more antennas may be used; more than one antenna may be used if “sectorized” transmission with high-gain antennas is desired to improve range while also enabling flexibility in the positioning of other devices that are providing energy and/or information. 
     The tag  200  is “battery-free” meaning that it does not receive power from any other source other than that which is stored on the capacitance of the energy storage capacitors C 1 -CN. The tag  200  is “autonomous” meaning that it does not rely on energy being transmitted by an external device at the same time that that tag  200  transmits information. As further described below, the microwave frequency transceiver  203  of the tag  200  generates its own microwave frequency carrier and modulates the carrier for data transmission rather than relying on an un-modulated carrier provided by an external device. Furthermore, the microwave frequency transceiver  203  can independently receive, demodulate and process information received via the one or more antennas. 
       FIG. 3  is a block diagram of a communication system  300  according to one embodiment of the present invention including the battery-free microwave frequency RF tag  200  communicatively coupled with a battery powered device  301  via bi-directional communication link  303 . The tag  200  includes at least one shared omni-directional antenna (e.g.,  201 ) or multiple high-gain shared antennas  201 - 201  which is/are used to harvest energy and send/receive data. The battery powered device  301  is a phone (cellular phone or smart phone or the like) or a tablet or similar type device which communicates according to at least one standard communication protocol, such as Wi-Fi or Bluetooth or the like. 
       FIG. 4  is a block diagram of a communication system  400  according to one embodiment of the present invention including the battery-free microwave frequency RF tag  200  communicatively coupled with the device  301  via a bi-directional communication link  403 , which further includes an energy transfer link  405  for transfer of energy from device  301  to tag  200 . The tag  200  includes at least one shared omni-directional antenna (e.g.,  201 ) or multiple high-gain shared antennas  201 - 201  which is/are used to send/receive data. The tag  200  further includes one or more antennas  206  coupled to the energy harvesting system  211  for energy transfer via the energy transfer link  405 . 
     The communication link  403  is according Wi-Fi or Bluetooth or the like, in which separate antennas are used for the microwave frequency transceiver  203  and the energy harvesting system  211 . In one embodiment, generally one (omni-directional) antenna is used for the microwave frequency transceiver  203  and one or more antennas  206  are used for the energy harvesting system  211 . In one embodiment, a separate energy harvesting circuit within the energy harvesting system  211  is coupled to each antenna  206 . 
     The energy transfer link  405  is facilitated in any one or more of several different communication methods. In one embodiment, the Wi-Fi or Bluetooth communications transmitted by the device  301  are also used for the energy transfer link  405  to provide energy for charging the capacitor(s) C 1 -CN. In an alternative embodiment, the device  301  provides energy via the energy transfer link  405  from cellular uplink transmissions. In this manner, separate frequency bands and protocols may be used for energy harvesting and data communications. In one embodiment, for example, the Wi-Fi or Bluetooth microwave frequency bands are used for communication and a transceiver in one or more of the licensed cellular bands provides energy to be stored for data communication use. It is noted that the communications via link  403  may occur at the same or a different and even mutually-exclusive time from the energy transfer via link  405 . While different antennas may likely be used in different bands, it is possible for all bands to be tuned using an antenna and associated passive network that are resonant in multiple bands, although at a potential reduction in efficiency. 
       FIG. 5  is a block diagram showing a wireless disposable wristband  501  incorporating a battery-free microwave frequency RF tag  503  (configured according to any of the embodiments of the tag  200  described herein) which communicates with the device  301  using microwave frequency communications according to one embodiment. In one embodiment, the device  301  is a smart phone or the like running a software application, in which the phone may read from and, in various embodiments, write to the tag  503  incorporated on the wristband  501 . The tag  503  contains sensors and/or stored information or the like, such as, for example, medical records, administered medications or procedures (like CT scans) that had been performed on a patient earlier during hospitalization. The wireless disposable wristband  501  may also include sensors such as relative body temperature, pulse, or a pulse oximeter (SPO2) (not shown). The microwave frequencies may include the bands used for Bluetooth or Wi-Fi and/or one or more of the licensed cellular bands as previously described. 
     The device  301  may further communicate with additional devices, such as an access point that routes its data to and from a server or the like over either the Internet or a closed intranet or the like. The server includes or is otherwise coupled to one or more storage devices. 
       FIG. 6  is a block diagram that shows a wireless advertisement or flyer (AD/FLYER)  601  incorporating a battery-free microwave frequency RF tag  603  (configured according to any of the embodiments of the tag  200  described herein) which communicates with the device  301  using microwave frequency communications according to one embodiment. The embodiment of  FIG. 6  is similar to that shown in  FIG. 5  in which the wireless AD/FLYER  601  and tag  603  replaces the wireless disposable wristband  501  and RF tag  503 . In one embodiment, the device  301  is a smart phone or the like running a software application, in which the phone may read from and, in various embodiments, write to the tag  603  incorporated on the wristband  501 . In this case, the wireless AD/FLYER  601  with tag  603  enables localized promotions to be deployed, for example, a coupon that enables an owner of the device  301  to receive a discount at a recently-opened nearby store in the same group or chain. It also allows localization of potential customers, as the tag  603  may communicate also with store infrastructure (e.g., a nearby Wi-Fi Access Point or AP). Microwave frequencies may include the bands used for Bluetooth or Wi-Fi and/or one or more of the licensed cellular bands. 
     In a similar manner, the device  301  may further communicate with additional devices, such as an access point that routes its data to and from a server or the like over either the Internet or a closed intranet or the like. The server includes or is otherwise coupled to one or more storage devices. 
       FIG. 7  is a block diagram that shows a wireless credit, debit, and/or loyalty card  701  incorporating a battery-free microwave frequency RF tag  703  (configured according to any of the embodiments of the tag  200  described herein) which communicates with the device  301  using microwave frequency communications according to one embodiment. The embodiment of  FIG. 7  is similar to that shown in  FIG. 5  in which the card  701  and tag  703  replaces the wireless disposable wristband  501  and RF tag  503 . In one embodiment, the device  301  is a smart phone or the like running a software application, in which the phone may read from and, in various embodiments, write to the tag  703  incorporated on the card  701 . In this case, the card  701  enables localized promotions to be deployed and offers the possibility of “one card in the wallet” for multiple purposes (identification (ID), payment, promotions). Microwave frequencies may include the bands used for Bluetooth or Wi-Fi and/or one or more of the licensed cellular bands. 
     In a similar manner as with  FIGS. 5 and 6 , the device  301  may further communicate with additional devices, such as an access point that routes its data to and from a server or the like over either the Internet or a closed intranet or the like. The server includes or is otherwise coupled to one or more storage devices. 
     In general, a tag is a device or label or the like that has at least the property that it retains and makes available information about something to which it is associated (e.g., a price tag on merchandise, a hospital wristband, etc.). It may also update its own information about the thing to which it is associated. In each of the configurations shown in  FIGS. 5-7 , a physical article, such as a physical body or physical object or the like, has a physical form to achieve a particular or predetermined purpose or function, in which an autonomous battery-free microwave frequency RF tag (e.g., tag  503 ,  603 ,  703  according to the embodiment of tag  200 ) is embedded or provided on the physical article to enhance the targeted purpose or function. The wristband  501 , for example, is physically configured to be held on a person&#39;s wrist, and the tag  503  stores or otherwise provides information associated with that person and/or a facility or event. The AD/FLYER  601  is physically configured to capture the attention of an onlooker or passer-by, and the tag  603  is provided on the AD/FLYER  601  to convey information or otherwise to offer a benefit to that person for a commercial or business purpose or the like of at least one commercial entity (e.g., localized promotion(s), coupon(s), discount(s), local business advertisement, etc.). The card  701  is physically configured in similar manner as a credit or debit card or the like to be carried by a person, and the tag  703  stores data and information to facilitate one or more commercial transactions (e.g., localized promotions, one card in the wallet, ID, payment, etc.). 
       FIG. 8  is a figurative diagram showing a portion or fragment of a basic protocol for charging a battery-free microwave frequency RF tag  803  and an initial response sent by the tag  803  for initialization of communications according to one embodiment. The tag  803  is configured according to any of the embodiments of the tag  200  described herein. A device  801 , which supplies energy to the tag  803 , sends a sequence of one or more charging packets  805  to the tag  803 . The charging packets  805  may be formatted in a manner to avoid any interoperability issues with other devices using the same band, such as those using the same protocol. In one embodiment, as further described below, the charging packets  805  may be beacons, which convey timing and network status information on a periodic basis, a form of Request, for example, a Request to Send (RTS) or data frame, or a form of Response, for example a Clear to Send (CTS) or data frame. Since there is no expectation of a response to a Beacon frame, a Beacon is a good choice for the charging packet  805 . A CTS sent to the sender&#39;s own device address also results in no expectation of a response. A RTS may be sent repeatedly. 
     Once sufficiently charged, the tag  803  returns a response  807  back to the device  801 . In this manner, further two-way communication may occur. It is appreciated that once the tag  803  is sufficiently charged, the response  807  may be sent autonomously by the tag  803 , such that it may be performed at any time even when the device  801  (or any other device) is not transmitting information or otherwise generating microwave energy in the wireless medium. The energy stored by the tag  803  may further be used at a somewhat later time to communicate with a different device. 
       FIG. 9  is a figurative diagram showing a fragment of the 802.11 WLAN protocol, in which charging a battery-free microwave frequency RF tag  903  is accomplished by beaconing according to one embodiment. A device  901 , which supplies energy to the tag  903 , sends a sequence of one or more beacons  905  to the tag  903 . The device  901  is configured as an access point (AP), a Personal Basic Service Set (PBSS) Central Point (PCP) device, a Wi-Fi Direct Group Owner, a member of a Wi-Fi Direct Group or an Independent Basic Server Set Station (IBSS STA) powered by a power supply or battery or the like. Subsequently the tag  903  responds with a probe request  907  and the two devices  901  and  903  become associated. 802.11 beacons typically include both implicit (based on relative temporal position to other transmitted frames) and explicit timing information (in the frame payload) for the Basic Service Set (BSS), point-to-point link or other type of network. 
     A variable number of beacons  905  is transmitted by the device  901  to charge the tag  903 . The particular number of beacons  905  is determined by a number of factors, such as the distance and/or orientation between the  901  and  903 . More time for charging (more beacons  905 ) may be needed for a larger distance between  901  and  903 , because less energy is harvested per packet due to loss in the wireless channel. Once a sequence of beacons  905  (usually with short beacon interval) has been transmitted and the tag  903  is sufficiently charged, the tag  903  may send a probe request  907  to the device  901  in an autonomous manner as illustrated. The probe request  907  is the first step in associating  901  and  903  in any band that allows active scanning by new devices for other devices. The device  901  responds with a probe response  909 , and other frame exchanges could then occur to enable the tag  903  to send and receive larger amounts of data to/from the device  901 . 
       FIG. 10  is a block diagram of an exemplary microwave energy harvesting and storage network  1000  implemented according to an embodiment of the present invention which may be used to implement the energy harvesting system  211  including each of one or more energy harvesting circuits within the system  211 . A passive network  1003  is coupled to an antenna  1001  for amplifying a received microwave signal in a particular band or band(s). The antenna  1001  and the passive network  1003  are collectively configured to generate the largest possible output voltage, shown as an AC voltage VRF. A rectifier &amp; energy storage circuit  1005  receives VRF and produces a DC voltage VDC which is stored by an energy-storage capacitance, such as the capacitor(s) C 1 -CN represented by a capacitor coupled between VDC and GND. A supply voltage generator circuit  1007  receives VDC and produces the regulated voltage VDD which is sufficiently accurate as a source voltage for digital and analog/RF circuits. The antenna  1001  represents any of the antennas  201 ,  204  and/or  206  previously described. 
     The passive network  1003  and the rectifier &amp; energy storage circuit  1005  collectively harvest and store energy received via one or more antennas. The term “harvest” and its various forms as used herein means the conversion of received microwave energy into energy (e.g., voltage) for storage on the storage capacitance, which is used to develop the supply voltage VDD for remaining circuitry in the tag device. 
     The passive network  1003 , the rectifier &amp; energy storage circuit  1005 , and the supply voltage generator circuit  1007  may each be implemented according to well-known or otherwise available configurations. 
       FIG. 11 , for example, shows several conventional configurations for implementing the passive network  1003 , including a wideband step-up transformer  1101 , an LC resonant structure  1103 , and a resonant pi-network  1105 . The wideband step-up transformer  1101  boosts a voltage of the antenna (shown as ANT) by a factor 1:N using magnetically-coupled coils to produce the output VRF. The voltage of VRF is thus N times larger than the antenna voltage ANT, and AC voltages within a large range of frequencies are boosted. The LC resonant structure  1103  includes an inductor L and capacitors CA and CB which are configured as illustrated to provide narrowband voltage gain from ANT to VRF. The resonant pi-network  1105  includes an inductor L and capacitors CA and CB which are configured as illustrated to implement a low-pass filter with cut-off frequency with adjustable in-band gain. Many other similar types circuits may be employed for implementing the passive network  1003 . 
       FIG. 12  shows several conventional configurations for implementing the rectifier &amp; energy storage circuit  1005 , each configured with a combination of one or more diodes and one or more capacitors, including a half-wave rectifier  1201 , a full-wave rectifier  1203 , a voltage doubling rectifier  1205  for producing higher DC output voltage, and a two series-stacked voltage doubling rectifier circuit  1207  for further increasing DC output voltage beyond that produced by  1205 . Many other similar types circuits may be employed for implementing the rectifier &amp; energy storage circuit  1005 . Each of the diodes may be configured in any suitable manner as known by those of ordinary skill in the art, such as a simple PN junction diode, a diode-connected metal-oxide semiconductor, field-effect transistor (MOSFET), a Schottky diode, a diode-connected bipolar junction transistor (BJT), etc. 
     The supply voltage generator  1007  may be configured using many types of voltage converters or regulators or the like as known by those of ordinary skill in the art, such as, for example, a switching DC-DC converter (buck, boost, buck-boost, etc.) or a low dropout (LDO) regulator or the like. 
       FIG. 13  is a schematic and block diagram of a microwave frequency radio transceiver  1300  which may be used to implement the microwave frequency transceiver  203  of the tag  200 . A media access control (MAC) device  1301  interfaces the controller  207  via the host bus  205  and is further coupled to a digital physical layer (PHY) device  1303 . The MAC  1301  and the TX PHY portion of the PHY device  1303  controls the radio and turns bits from the controller  207  into modulated symbols (e.g. BPSK or QPSK constellation points or an OFDM multiplex with some sub-carrier constellations), in which the modulated symbols are interpolated and pulse-shaped and then provided to the input of a digital to analog converter (DAC)  1305 . The MAC  1301  and/or the digital PHY  1303  and/or the DAC  1305  individually or collectively form a frame generation circuit. The analog output of the DAC  1305  is provided to the input of a low-pass filter (LPF)  1307  for removing aliases from the DAC  1305 . The LPF  1307  may provide gain or attenuation. The filtered output of the LPF  1307  is provided to an input of an in-phase quadrature-phase (90-degree) mixer  1309 , which translates the filtered signal from baseband (centered at DC) to some relatively-higher carrier frequency, e.g., 2.4-2.5 GHz. The mixer  1309  may be referred to as a modulator circuit for information to be transmitted, and further as a demodulator circuit for received information. 
     The transceiver  1300  includes a carrier frequency generator  1311 , which includes an oscillator  1313  generating a frequency reference signal F REF . The oscillator  1313  may be implemented by a crystal oscillator or the like and may be simply pass through an externally-generated F REF  reference frequency signal. The F REF  signal provides the input to a Phase-Locked Loop (PLL)  1315  and a voltage controlled oscillator (VCO)  1317  for generating the microwave carrier frequency signal MC. The MC signal is provided to an input of the mixer  1309 . A TX output of the mixer  1309  is provided to the input of a power amplifier (PA)  1319  to amplify the signal for transmission at a greater distance in the wireless channel. In one embodiment, the PA  1319  is provide to an input of a matching network  1321 , which provides additional passive gain in the receiver path. The matching network  1321  is coupled to an antenna  1001  for transmitting a data packet in the wireless channel. The antenna  1001  represents any of the antennas  201 ,  204  and/or  206  previously described. In an alternative embodiment, the matching network  1321  is not provided and the output of the PA  1319  drives the antenna  1001 . The DAC  1305  and the LPF  1307  and/or the mixer  1309  and/or the PA  1319  and/or the matching network  1321  may be individually or collectively referred to as a transmitter circuit. 
     In the receiver path, signals received via the antenna  1001  are provided through a receiving circuit including the matching network  1321  (if provided), which in one embodiment is a high-gain passive matching network in the receive path. The received signal is shown provided to a variable attenuator  1323  (also part of the receiver circuit) which feeds an RX input of the mixer  1309 . The mixer  1309  reduces the frequency of the received signal from a relatively-higher frequency to some relatively lower frequency, e.g., baseband (DC) or a low intermediate frequency (IF) such as 1 MHz. The baseband signal output from the mixer  1309  is provided to an LPF  1325  which blocks out-of-channel and out-of-band interference and which may provide additional gain or attenuation. The output of the LPF  1325  is operably coupled to a variable gain amplifier (VGA)  1327 , which may provide larger values of gain after removing adjacent-channel interference. The output of the VGA  1327  is coupled to an analog to digital converter (ADC)  1329 , which provides a sampled, quantized representation of the input signal to the RX PHY portion of the digital PHY  1303 . The output of the RX PHY is provide to the MAC  1301 . The RX PHY and the MAC  1301  control the radio and demodulates the output samples of the ADC  1329  and then decodes the bits intended for the tag device. The bits are provided to the controller  207  via the host bus  205 . The MAC  1301  and/or the digital PHY  1303  and/or the ADC  1329  individually or collectively form a frame processing circuit. 
     It is appreciated that the microwave frequency transceiver  203  may be implemented according to many alternative configurations. The microwave frequency transceiver  1300  enables any of the tags described herein to be autonomous since it generates its own microwave frequency carrier (e.g., MC) which is used for communications including transmitting data to external devices. Data communications and energy harvesting may each occur on any one or more of multiple microwave frequency bands. The microwave frequency communications may be implemented according to any one or more of the standard communication protocols, such as Wi-Fi or Bluetooth or the like, for enabling communication with common devices, such as smart phones or the like. 
     Although the present invention has been described in considerable detail with reference to certain preferred versions thereof, other versions and variations are possible and contemplated. For example, the circuits described herein may be implemented in any suitable manner including logic devices or circuitry or the like. The circuits described herein may include inverting devices implementing positive or negative logic or the like in which any signal may be inverted. The present invention is described using circuits operating with digital or binary bytes and words where it is understood that the circuitry applies to digital or binary values comprising any number of bits. Those skilled in the art should appreciate that they can readily use the disclosed conception and specific embodiments as a basis for designing or modifying other structures for carrying out the same purposes of the present invention without departing from the spirit and scope of the invention as defined by the appended claims.

Metadata:
Filing Date: 20110422
Publication Date: 20140805
Grant Date: 20140805
Priority Date: 20100427
Inventors: COOK BENJAMIN W.
BERNY AXEL D.
TRACHEWSKY JASON A.
Assignee: APPLE INC
CPC Classifications: [{"code": "G06K19/0708", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06K19/0708", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06K19/07749", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06K19/07749", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 44815317