Abstract:
A radio frequency identification (RFID) tag comprises a transceiver and a component coupled to the transceiver. The transceiver is adapted to wirelessly receive power from an RFID reader and/or from a mobile communication device. The power received from the mobile communication device is used to power the component, providing an alternative power source (cellular beacons) that uses no additional handset power.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Technical Field 
         [0002]    The present disclosure relates generally to a wireless device that receives radio frequency (RF) energy from multiple RF transmission sources. More specifically, the present disclosure relates to an radio frequency identification (RFID) tag that, in addition to receiving RF energy from a corresponding RFID reader for RFID data communications, also receives RF energy from another wireless device, such as a cellular telephone, to power a component (e.g., a sensor) in the tag. 
         [0003]    2. Background Information 
         [0004]    Radio frequency identification (RFID) communications typically occur between an RFID-enabled reader and an RFID-enabled tag. The reader and the tag each comprise transceivers that wirelessly communicate with each other. In some implementations, the tag is passive. A passive tag does not have its own source of power and is thus temporarily powered by radio frequency (RF) energy transmitted by a near-by reader. The effective communication range for a reader and tag is typically fairly limited. In the absence of a reader (and its transmitted RF energy), a passive tag is generally unable to be powered on and perform useful work. 
       BRIEF SUMMARY 
       [0005]    In accordance with at least some embodiments of the invention, a radio frequency identification (RFID) tag comprises a transceiver and a component coupled to the transceiver. The transceiver is adapted to wirelessly receive power from an RFID reader and from a mobile communication device. The power received from the mobile communication device is used to power the component. 
       NOTATION AND NOMENCLATURE 
       [0006]    Certain terms are used throughout the following description and claims to refer to particular system components. As one skilled in the art will appreciate, different companies may refer to a component by different names. This document does not intend to distinguish between components that differ in name but not function. In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . .”. Also, the term “couple” or “couples” is intended to mean either an indirect or direct connection. Thus, if a first device couples to a second device, that connection may be through a direct electrical or wireless connection, or through an indirect electrical or wireless connection via other devices and connections. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    For a more detailed description of the preferred embodiments of the present invention, reference will now be made to the accompanying drawings, wherein: 
           [0008]      FIG. 1  shows a system in accordance with preferred embodiments of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0009]    The following discussion is directed to various embodiments of the invention. Although one or more of these embodiments may be preferred, the embodiments disclosed should not be interpreted, or otherwise used, as limiting the scope of the disclosure, including the claims, unless otherwise specified. In addition, one skilled in the art will understand that the following description has broad application, and the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to intimate that the scope of the disclosure, including the claims, is limited to that embodiment. 
         [0010]      FIG. 1  shows a preferred embodiment of the invention in which a reader  24  is able to wirelessly communicate with a tag  30 . A mobile communication device  40  (e.g., a cellular telephone, wireless PDA, etc.) is also shown. The reader  24  comprises a transceiver  26 . The tag  30  comprises a transceiver  32  and a component  34 . If desired, other components may be included within the reader  24  and tag  30 . The reader  24  and tag  30  may be RFID-compliant in accordance with some embodiments, and comply with other communication protocols in accordance with other embodiments. 
         [0011]    Via the transceivers  26  and  32 , the mobile device  20  and tag  30  wirelessly communicate with each other. In accordance with one embodiment of the invention, the reader  24  and the tag  30  are provided in accordance with the radio frequency identification (RFID) protocol. As such, the reader  24  comprises an RFID reader and the tag  30  comprises an RFID tag. Unless otherwise specified, as used herein, the term “tag” is not limited to the RFID context. The tag  30  preferably is positioned at a fixed location such as on a wall, furniture, or piece of equipment. Other embodiments comprise wireless devices other than RFID-based devices. For example, devices  24  and  30  may comprise ultra wide band (UWB) transceivers. The mobile communication device  40  preferably is not an RFID reader or RFID-compliant at all. 
         [0012]    The reader  24  emits a periodic wireless beacon signal that, when in range of the tag&#39;s transceiver  32 , causes the tag  30  to automatically echo back a wireless response signal along with an identifier associated with the tag. In general, the transceiver  32  reflects RF power (received from the reader) in a coded manner back to the reader  24 . In at least some embodiments, the identifier differentiates the tag  30  from other tags. Upon receipt of the response signal, the reader  24  is able to determine that the reader is within range of the tag  30 . The reader&#39;s  24  beacon signal may be automatically emitted at predetermined fixed or programmable periodic intervals. Additionally or alternatively, the reader  24  can be manually activated by its user to emit a beacon. 
         [0013]    The tag  30  preferably is “passive” meaning that the tag does not have its own source of power. Instead, the tag&#39;s transceiver  32  derives power for the tag to operate from the wireless signal received from the reader  24 . In accordance with embodiments of the invention, the tag&#39;s transceiver also derives power from wireless signals transmitted by the mobile communication device  40 . In embodiments in which the mobile communication device  40  comprises a cellular telephone, the communication device emits periodic wireless signals (“beacons”) to associate with, or maintain association with, a base station. When the tag  30  is within range of the mobile communication device  40  and is not in operative communication with reader  24 , such periodic cellular signals transmitted from the mobile communication device are detected by the transceiver  32  in the tag  30  even though such wireless signals were intended for a base station for association purposes. In effect, tag  30  extracts operational power from cellular signals transmitted by the mobile communication device  40  intended for a base station. 
         [0014]    The tag&#39;s receiver may be designed to operate in several modes. (1) Operation as a standard RFID receiver in which the tag gathers energy via RF interrogation at the standard RFID frequencies. (2) Operation as a cellular-mode receiver, in which energy is gathered from one or more of the standard cellular uplink frequencies. Beacons from the cellular handset may be used to prompt the RFID device to transmit its information or to perform other information gathering tasks as outlined below. Transmission (reflection/translation) of the RFID signal is in the RFID band. In this mode, energy harvesting of a nearly continuous RF signal source occur. (3) Operation as a dual-mode receiver, gathering energy from either standard RFID or cellular frequencies. In this mode, prompting of the RFID device may be either through the RFID or cellular frequency signals. As before, the reflection/translation of the RFID interrogation signal is in the RFID band. ( 4 ) Operation in which the Radio frequency source is not restricted to a standard RFID reader or cellular frequency signals. 
         [0015]    The electrical power derived by the tag&#39;s transceiver  32  from the mobile communication device  40  preferably is used to power the component  34 . The component  34  can be any type of, or part of, a peripheral device. Examples of such a peripheral device include a keyboard and a sensor. As a sensor, the component  34  may comprise a temperature sensor, a pressure sensor, or a physiological sensor (i.e., a sensor implanted in the human body). With power derived from the mobile communication device&#39;s wireless signal, the tag could power up the component  34  to, for example, take a reading such as temperature, pressure, blood oxygen level, etc. The reading could then be stored in non-volatile memory in the component  34  or transceiver  32  for transmission to the mobile communication device  40  or reader  24 . 
         [0016]    In accordance with at least some embodiments of the invention, the component  34 , and tag  30  in general, preferably can be effectively operated with brief spurts of operational power provided by the received RF power, rectified and stored in a capacitor or equivalent component. That is, the tag  30  should be able to perform a task, or at least part of task, with power provided to it at discrete times. For example, the mobile communication device  40  may emit beacons at a rate of 5 beacons per second. The tag  30 , and component  34  specifically, preferably operate to perform the function associated with the component  34  (e.g., sensor) with power arriving briefly 5 times per second. 
         [0017]    The ability of the device  30  to harvest energy from mobile devices such as cell phones and WIFI devices enables the passive tag to perform other operations without an RFID reader such as capturing and recording environmental information via, for example, integrated temperature, light, pressure, RF, or audio sensors. In the case of RF sensing, the tag may be capable of receiving energy over a broad spectrum of frequencies. It may be able to capture and record the ID of a beaconing GSM cell phone or a mobile WIFI, BT, or WIMAX device. In the case of RF sensing, the RFID device  30  behaves in one mode as a normal RFID device when it is communicated with using specified standard protocols. Device  30  may behave as a mobile device powered sensor/recorder whenever a nearby mobile device provides signal strength strong enough for it to do so and the device  30  is not in operative communication with RFID reader  24 . In this latter mode of operation, the device may simply write to an internal circular buffer (e.g., in the component  34 ) the data that it has sensed. If there is some means of extracting relative state or time between sensed events, so that the device may avoid writing multiple data points it recognizes to have occurred close together in time and may record whatever reference information might be utilized to extract a time base in the future. In the case of RF sensing, since a GSM cell phone (or a WIFI/WIMAX/BT device) is known to beacon at regular intervals, the beacons of one of these nearby stationary devices may be used to establish a time base for other sensed events. 
         [0018]    In one embodiment, the tag might be considered a “snoop” tag which records a list of wirelessly beaconed IDs or medium access control (MAC) addresses over time. Such “snoop” tags may be placed at entry and exit points of public spaces (and transportation systems such as aircraft) to monitor for suspected criminals or unauthorized persons. A security person may scan the tags with a mobile device comprising an integrated RFID reader that connects to a network to flag potential suspects. 
         [0019]    In some embodiments, the component  34  can be operated with power derived from both the reader  24  and mobile communication device  40  simultaneously or at different times depending on which of the reader  24  or mobile communication device  40  is within range of the tag  30 . 
         [0020]    While the preferred embodiments of the present invention have been shown and described, modifications thereof can be made by one skilled in the art without departing from the spirit and teachings of the invention. For example, the communication between the communication device and tag/reader can be infra-red (IR)-based instead of radio frequency (RF)-based as in the case of RFID. Further, in some embodiments, the tag wirelessly receives power from an external radio frequency (RF) source other than an RFID reader or mobile communication device. The scope of protection is not limited by the description set out above. Each and every claim is incorporated into the specification as an embodiment of the present invention.