Abstract:
An RFID reader for communicating with an RFID tag and with a remote RF transceiver. A single transceiver is employed for communicating with RFID tags and with a remote RF transceiver. A single antenna is coupled to the transceiver. In a first mode, the transceiver communicates with the RFID tags via the antenna, on a first frequency. In a second mode, the transceiver communicates with the remote RF transceiver via the same antenna, on the first frequency or a second frequency.

Description:
RELATED APPLICATIONS  
       [0001]     This application claims priority to provisional patent application Ser. No. 60/673,692, filed Apr. 21, 2006 and 60/712,957, filed Aug. 31, 2005. The disclosures of which are incorporated herein by reference. 
     
    
     BACKGROUND  
       [0002]     RFID stands for Radio-Frequency IDentification. An RFID transponder, or ‘tag’, serves a similar purpose as a bar code or a magnetic strip on the back of a credit card; it provides an identifier for a particular object, although, unlike a barcode or magnetic strip, some tags support being written to. An RFID system carries data in these tags, and retrieves data from the tags wirelessly. Data within a tag may provide identification for an item in manufacture, goods in transit, a location, the identity of a vehicle, an animal, or an individual. By including additional data, the ability is provided for supporting applications through item-specific information or instructions available upon reading the tag.  
         [0003]     A basic RFID system includes a reader or ‘interrogator’ and a transponder (RFID tag) electronically programmed with unique identifying information. Both the transceiver and transponder have antennas, which respectively emit and receive radio signals to activate the tag, read data from the tag, and write data to it. An antenna is a feature that is present in both readers and tags, and is essential for the communication between the two. An RFID system requires, in addition to tags, a mechanism for reading or interrogating the tags and usually requires some means of communicating RFID data to a host device, e.g., a computer or information management system. Often the antenna is packaged with the transceiver and decoder to become a reader (an ‘interrogator’), which can be configured either as a handheld or a fixed-mount device. The reader emits radio waves in ranges of anywhere from one inch to 100 feet or more, depending upon its power output and the radio frequency used. When an RFID tag passes through the electromagnetic zone (its ‘field’) created by the reader, it detects the reader&#39;s activation signal upon which it conveys its stored information data. The reader decodes the data encoded in the tag&#39;s integrated circuit and the decoded data is often passed to a device (e.g., a computer) for processing.  
         [0004]     The word transponder, derived from TRANSmitter/resPONDER, indicates the function of an RFID tag. A tag responds to a transmitted or communicated request for the data it carries, the communication between the reader and the tag being wireless across the space between the two. The essential components that form an RFID system are one or more tags and a reader or interrogator. The basic components of a transponder are, generally speaking, fabricated as low power integrated circuit suitable for interfacing to an external coil, or utilizing ‘coil-on-chip’ technology, for data transfer and power generation, where the coil acts as a tag antenna matched to the frequency supported.  
         [0005]     In operation, RFID tags require power, even though the power levels required for operation are invariably very small (microwatts to milliwatts). RFID tags are categorized as active, passive, or semi-active/semi-passive, the designation being determined by the manner in which a particular device derives its power. Active RFID tags are powered by an internal battery and are typically read/write devices. Passive tags operate without an internal battery source, deriving the power to operate from the field generated by the reader. Passive tags are consequently much lighter than active tags, less expensive, and offer a virtually unlimited operational lifetime. However, a passive tag must be powered without interruption during communication with the reader. Passive tags offer advantages in terms of cost and longevity, as they have an almost infinite lifetime and are generally less expensive than active tags.  
         [0006]      FIG. 1  is a diagram of a prior art RFID reader  100 . As shown in  FIG. 1 , reader  100  includes two radio modules, where one radio module  110  provides communication with RFID tags (transponders)  105  and a second radio module  120  provides RF backhaul communication with a transceiver  104 . Both radio modules  110 / 120  are connected to a (reader-enabled) device processor  101 , which is coupled with device hardware  110 / 120 / 102 . The radio modules  110 / 120  are essentially redundant, in that each module includes an identical or similar radio transceiver  114 / 124 , as well as a radio processor  112 / 122 . Furthermore, each radio module  110 / 120  requires a separate antenna  131 / 132 .  
         [0007]     RFID radio module  110  is shown utilizing a circulator  138  (which can, alternatively, be a directional coupler or a diode detector circuit) to selectively direct the received signal to the receiver  118 , allowing the transmitted signal from transmitter  116  to pass through to antenna  131 , while blocking the received signal from the output of transmitter  116 , and while blocking the transmit signal from the input of the receiver  118 . Backhaul RF radio module  120  is shown utilizing a transmit/receive (T/R) switch  139  to direct the received signal either to the receiver  138 , or to output the transmitted signal from transmitter  136  to antenna  132 . Radio module  120  could alternatively employ a circulator (or equivalent device)  138 .  
         [0000]     Problem to be Solved  
         [0008]     In order to read passive RFID tags, an RFID reader&#39;s radio transmitter is required to be turned on while the receiver is receiving. Previously existing RFID readers have accommodated this requirement by the use of directional couplers or the like. However, these previous RFID readers nevertheless employ redundant circuitry, including redundant radio modules, one module for communication with RFID tags and another module for communication with a host computer or server, via a backhaul RF transceiver.  
         [0009]     In addition, each of the radio modules employed by previous RFID readers typically uses its own radio processor. Furthermore, each of these radio modules employs a separate antenna, thus necessitating the use of at least two antennas for communication with both a tag and a backhaul transceiver. Elimination of these redundant components is thus desirable, to minimize power consumption, and to reduce the number of components and circuit size, thereby also reducing the cost of the reader.  
       SOLUTION TO THE PROBLEM  
       [0010]     A system and method are disclosed for providing the capability for an RFID reader to communicate with RFID tags and with a remote RF transceiver. A single transceiver is employed for communicating with both the RFID tags and with the remote RF transceiver. A single antenna is coupled to the transceiver. In a first mode, the transceiver communicates with the RFID tags via the antenna, on a first frequency. In a second mode, the transceiver communicates with the remote RF transceiver via the same antenna, on the same frequency or on a second frequency. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  is a diagram of a prior art RFID reader, showing the use of two radios to provide corresponding RF and RFID communication;  
         [0012]      FIG. 2  is a diagram of an exemplary embodiment of the present combined RFID reader and RF transceiver, showing high-level architecture of the system;  
         [0013]      FIG. 3  is a diagram of system components in one embodiment of the present system, in which RFID +RF backhaul radio processor code is located in the device processor;  
         [0014]      FIG. 4  is a diagram of system components in one embodiment of the present system, in which RFID +RF backhaul radio processor code is located in a combined RFID +RF backhaul radio module;  
         [0015]      FIG. 5  is a flowchart showing an exemplary set of steps performed in RF backhaul transmission and receiving, in one embodiment of the present system; and  
         [0016]      FIG. 6  is a flowchart showing an exemplary set of steps performed in RFID transmission and receiving, in one embodiment of the present system. 
     
    
     DETAILED DESCRIPTION  
       [0017]      FIG. 2  is a diagram of an exemplary embodiment of the present combined RFID reader and RF transceiver  200 , showing high-level architecture of the system. As shown in  FIG. 2 , the present embodiment comprises a combined RFID and RF backhaul radio transceiver module  202 , which is connected to a device processor  201 , which typically performs functions specific to the task or application for which the device was designed. Combined RFID+RF radio module  202  uses a single antenna  203  to send signals to, and receive signals from RFID tags  105 , as well as for communication with remote RF transceiver  104 . Remote transceiver  104  is typically coupled to a host computer or server (not shown), and is used to exchange data between one or more RFID tags and the host computer/server (i.e., backhaul communication). In some cases remote transceiver  104  may be a mobile device such as a wireless sensor network device (i.e., a mote).  
         [0018]     In an exemplary embodiment, an IEEE 802.15.4 compliant (‘ZigBee’) radio, operating at approximately 900 MHz is used by the present system to achieve standard ZigBee communication to a host and/or passive UHF RFID communication with EPC (Electronic Product Code) transponders (RFID tags). Alternatively, the present system may employ RF frequencies other than 900 MHz, as well as communication protocols other than IEEE 802.15.4.  
         [0019]      FIG. 3  is a diagram showing system components in one embodiment  300  of the present system. As shown in  FIG. 3 , in combined RFID reader and RF transceiver  300 , combined RFID and RF backhaul radio processor executable code  303  is located in the device processor  201 . Combined RFID and RF backhaul radio module  202  includes a combined transceiver  304 , comprising a combined RFID and RF backhaul radio transmitter  305 , and a combined RFID and RF backhaul radio receiver  306 . In one embodiment, communication between the RFID portion of the combined RFID/RF backhaul module  202 / 402  in systems  200 / 300 / 400  and RFID tags  105  takes place at approximately 900 MHz, and communication between modules  202 / 402  and RF transceiver  104  in systems  200 / 300 / 400  occurs at an offset of approximately 2 MHz, e.g., at approximately 902 or 898 MHz.  
         [0020]     Radio transmitter  305  and radio receiver  306  are connected to switching device  307 , which is connected to combined RF backhaul/RFID antenna  203 , and controlled by device processor  201 . In an exemplary embodiment, switching device  307  includes a double pole, single throw transmit/receive (‘T/R’) switch  309  and a circulator  308 . Circulator  308  is a signal directing (and isolating) device having a junction of three ports in which the ports can be accessed in such an order that when a signal is fed into any port it is transferred to the next port.  
         [0021]     In RFID communication mode, switch  309  is set to the closed (‘C’) position, and circulator  308  allows the signal from the output OP of transmitter  305  to flow to antenna  203 , while allowing the signal from the antenna to flow through switch  309  to the input IP of receiver  306 , while effectively blocking the signal from the antenna from reaching the transmitter output and effectively blocking the output signal from the transmitter  305  from reaching the receiver  306  input.  
         [0022]     The function provided by circulator  308  may, alternatively, be provided by other signal directing devices including a directional coupler, a diode detector, a mixer, or the like.  
         [0023]      FIG. 4  is a diagram showing system components in one embodiment  400  of the present system. As shown in  FIG. 4 , combined RFID reader and RF transceiver  400  includes a combined RFID and RF backhaul radio module  402 , including a combined RFID and RF backhaul radio processor  401  and associated executable code  403 . Radio processor  401  is connected to device processor  201  and to combined transceiver  304 , which includes a combined RFID and RF backhaul radio transmitter  305 , and a combined RFID and RF backhaul radio receiver  306  as in transceiver  304  described with respect to  FIG. 3 . Radio processor  401  is controlled by device processor  201 , and in turn, controls combined transceiver  304 .  
         [0024]     Similarly, with respect to  FIG. 3 , radio transmitter  305  and radio receiver  306  are connected to switching device  307 , which is connected to RFID/RF backhaul antenna  203  and controlled by device processor  201 , or alternatively, by radio processor  401 . The operation of switching device  307  is described in detail below with respect to  FIG. 5  and  FIG. 6 .  
         [0025]     The configuration of the components (e.g., signal directing/isolating device  308  and switch  309 ) shown in switching device  307  is one of a number of possible component configurations that may be employed to allow the shared use of combined RFID/RF radio backhaul module  202 / 402  with a single antenna  203 . Switching device  307  may alternatively include a directional coupler, a diode detector circuit, a mixer, or the like, to provide the functionality of circulator  308 . In an alternative embodiment, switch  309  may be eliminated in switching device  307 , in which case input IP of receiver  306  is connected directly to port  333  of device  308 , to provide full-duplex operation for RF backhaul mode.  
         [0026]      FIG. 5  is a flowchart showing an exemplary set of steps performed in RF backhaul communication between systems  200 / 300 / 400  and transceiver  104  (shown in  FIG. 2 ), in one embodiment of the present system. RF backhaul transmission can be divided into two phases or modes, an RF transmission mode  501 , and an RF receiving mode  511 . Operation of the present system is best understood by viewing  FIGS. 3 and 4  in conjunction with  FIG. 5 .  
         [0027]     As shown in  FIG. 5 , in RF backhaul transmission mode  501 , at step  505 , T/R switch  309  opens the direct connection from antenna  203  to radio receiver input IP, as indicated by the switch connection to position “O”. This allows the RF backhaul transmit signal to flow through circulator  308  out to antenna  203  and to RF transceiver  104  (shown in  FIG. 2 ), at Step  510 .  
         [0028]     In RF backhaul receiving mode  511 , at step  515 , RF transmitter  305  is shut off, and at step  520 , T/R switch  309  closes the connection from antenna  203  to receiver input IP, as indicated by the switch connection to position “C”, so that the antenna is directly connected to the RF receiver input. This allows the RF signal to be received from RF Transceiver  104 , at step  525 .  
         [0029]      FIG. 6  is a flowchart showing an exemplary set of steps performed in RFID communication between systems  200 / 300 / 400  and RFID tag  105 , in one embodiment of the present system. RFID communication can be divided into two phases or modes, an RFID transmission mode  601 , and an RFID receiving mode  611 . Operation of the present system is best understood by viewing  FIGS. 3 and 4  in conjunction with  FIG. 6 .  
         [0030]     As shown in  FIG. 6 , at step  605 , initially, RFID receiver  306  and RFID transmitter  305  are turned on and switch  309  is set to the open (‘O’) position. At step  610 , the transmitter  305  modulates the continuous wave (CW) transmit signal (this is the tag command signal). In one example of step  610 , device processor software (code  303  in device processor  201  in system  300 ) or software in radio processor  401  (code  403  in combined RFID/RF backhaul radio processor  401  in system  400 ) sends control signals to device hardware  102  (shown in  FIG. 2 ) to modulate the CW to send a command to the tag.  
         [0031]     At step  615 , the CW transmit signal from transmitter  305  flows through circulator  308  and out through antenna  203 . At step  620 , while transmitter  305  remains on, the T/R switch remains open and circulator  308  blocks the large transmitted signal and passes the signal received from the RFID tag to the input IP of receiver  306 . At step  625 , the RFID receiver  306  receives the modulated continuous wave (CW) RF signal from RFID tag  105 . During communication with RFID tag  105 , transmitter  305  remains broadcasting the CW signal to keep the tag energized, as indicated in block  615 . At step  625 , RFID tag  105  sends its data to the reader  200 / 300 / 400  by load modulating the backscattered CW wave that is being transmitted by RFID tag  105 .  
         [0032]     Certain changes may be made in the above methods and systems without departing from the scope of that which is described herein. It is to be noted that all matter contained in the above description or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense. For example, the methods shown in  FIGS. 5 and 6  may include steps other than those shown therein, and the systems shown in  FIGS. 2-4  may include different components than those shown in the drawings. The elements and steps shown in the present drawings may be modified in accordance with the methods described herein, and the steps shown therein may be sequenced in other configurations without departing from the spirit of the system thus described. The following claims are intended to cover all generic and specific features described herein, as well as all statements of the scope of the present method, system and structure, which, as a matter of language, might be said to fall there between.