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A multi-protocol RFID interrogating system employs a synchronization technique (step-lock) for a backscatter RFID system that allows simultaneous operation of closely spaced interrogators. The multi-protocol RFID interrogating system can communicate with backscatter transponders having different out

A multi-protocol RFID interrogating system employs a synchronization technique (step-lock) for a backscatter RFID system that allows simultaneous operation of closely spaced interrogators. The multi-protocol RFID interrogating system can communicate with backscatter transponders having different output protocols and with active transponders including: Title 21 compliant RFID backscatter transponders; IT2000 RFID backscatter transponders that provide an extended mode capability beyond Title 21; EGO™ RFID backscatter transponders, SEGO™ RFID backscatter transponders; ATA, ISO, ANSI AAR compliant RFID backscatter transponders; and IAG compliant active technology transponders. The system implements a step-lock operation, whereby adjacent interrogators are synchronized to ensure that all downlinks operate within the same time frame and all uplinks operate within the same time frame, to eliminate downlink on uplink interference.

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1. An RFID interrogator system comprising first and second RFID interrogators, each interrogator comprising elements a through e as follows: (a) a computer comprising a storage memory area and a processor, the computer being arranged for storing and selectively retrieving configuration parameters as

1. An RFID interrogator system comprising first and second RFID interrogators, each interrogator comprising elements a through e as follows: (a) a computer comprising a storage memory area and a processor, the computer being arranged for storing and selectively retrieving configuration parameters associated with plural RFID protocols;(b) a set of configuration parameter data for plural RFID protocols stored within the computer;(c) a protocol schedule comprising information representing a sequence in which different protocols shall be implemented;(d) a transceiver component connected to the computer via a data interface, said transceiver component being arranged to alter said transceiver component's operation in response to configuration parameter data received from the computer via the data interface;(e) wherein the computer automatically switches said transceiver component's operation among two or more protocols by retrieving said configuration parameter data and sending said configuration parameter data via the data interface to the transceiver component in accordance with the protocol schedule; wherein the first RFID interrogator further comprisesa synchronization signal generator comprising a global positioning satellite (GPS) receiver, said synchronization signal generator producing a system synchronization signal derived at least in part from a received GPS signal; andwherein the second RFID interrogator receives said system synchronization signal via a synchronization circuit. 2. The RFID interrogator of claim 1 wherein the configuration parameter is selected from the group consisting of: transmit depth of modulation; transmit duty cycle; transmit power; and receive sensitivity. 3. The RFID interrogator of claim 1 wherein the configuration parameter is transmit depth of modulation. 4. The RFID interrogator of claim 3 wherein the data interface comprises a digital to analog converter producing an output and the transceiver component comprises a switch which selects whether a transmitted signal is derived from the output of the digital to analog converter or a separate voltage reference. 5. The RFID interrogator of claim 1 wherein the configuration parameter is transmit duty cycle. 6. The RFID interrogator of claim 5 wherein the data interface comprises a microcontroller data register controlling a UART and the transceiver component comprises a UART output circuit. 7. The RFID interrogator of claim 1 wherein the configuration parameter is transmit power. 8. The RFID interrogator of claim 7 wherein the data interface comprises a digital to analog converter producing an output; and the transceiver component comprises a variable attenuator that varies an amplitude of a transmitted signal based upon the output of the digital to analog converter. 9. The RFID interrogator of claim 1 wherein the configuration parameter is receive sensitivity. 10. The RFID interrogator of claim 9 wherein the data interface comprises a digital control signal from the computer and the transceiver component comprises a variable attenuator which is controlled by the digital control signal. 11. A method of operating first and second RFID interrogators each comprising a computer comprising a storage memory area and a processor, the computer being arranged for storing and selectively retrieving configuration parameter data related to a configuration parameter associated with plural RFID protocols said method comprising the steps of: (a) storing in the computer a set of configuration parameter data for plural RFID protocols;(b) providing a protocol schedule comprising information representing a sequence in which different protocols shall be implemented;(d) altering the operation of a transceiver component connected to the computer via a data interface in response to said configuration parameter data received from the computer;(e) automatically switching said transceiver component operation among two or more protocols by retrieving said configuration parameter data and sending said configuration parameter data via the data interface to the transceiver component in accordance with the protocol schedule; and(f) synchronizing the first and second RFID interrogators with a synchronization signal derived at least in part from a received GPS signal. 12. The method of claim 11, wherein the configuration parameter is transmit depth of modulation and wherein the data interface comprises a digital to analog converter producing an output and the transceiver component comprises a switch, the method further comprising the step of selecting whether a transmitted signal is derived from the output of the digital to analog converter or a separate voltage reference by controlling said switch. 13. The method of claim 11, wherein the configuration parameter is transmit duty cycle, wherein the data interface comprises a microcontroller data register controlling a UART and the transceiver component comprises a UART output circuit. 14. The method of claim 11, wherein the configuration parameter is transmit power, wherein the data interface comprises a digital to analog converter producing an output; and the transceiver component comprises a variable attenuator; the method further comprising the step of varying an amplitude of a transmitted signal with said variable attenuator based upon the output of said digital to analog converter. 15. The method of claim 11, wherein the configuration parameter is receive sensitivity wherein the data interface comprises a digital control signal from the computer and the transceiver component comprises a variable attenuator, the method further comprising controlling receiver sensitivity by controlling said variable attenuator with said digital control signal. 16. The method of claim 11, further comprising the second RFID interrogator starting its protocol schedule in response to said synchronization signal.