Extending the Read Range of Passive RFID Tags

Abstract

An embodiment of the present invention improves the efficiency of radio frequency identification (RFID) systems and helps to extend the effective read range for certain configurations of closely spaced RFID tags. Specifically, an embodiment helps to minimize energy losses that result when there is excess energy from the excitation source. Various embodiments are directed toward using only as much of the excitation energy as necessary to power the RFID circuitry. An embodiment may have the benefit of making more of the excitation energy available to power other RFID tags nearby—thereby improving system performance and read range.

What is claimed is: 
     
         1 . A method of performing radio frequency identification (RFID), comprising the steps of:
 (a) generating, by an RFID reader, an excitation signal that includes a first read command;   (b) generating, by a first plurality of RFID tags, a first plurality of responses as part of the excitation signal;   (c) decoding, by the RFID reader, the first plurality of responses from the excitation signal;   (d) transmitting, by the RFID reader, a sleep command to each of the first plurality of RFID tags using the excitation signal;   (e) decoupling, by the first plurality of RFID tags, from an excitation field generated by the excitation signal, in response to the sleep command; and   (f) repeating (a), (b), (c), (d) and (e) for a second plurality of RFID tags.   
     
     
         2 . An apparatus including a circuit for performing radio frequency identification (RFID), comprising:
 an antenna; and   RFID electronics, coupled to the antenna, that is configured to activate in response to receiving an excitation signal, to generate a response as part of the excitation signal, to receive a sleep command as part of the excitation signal, and to decouple from an excitation field generated by the excitation signal, in response to the sleep command.   
     
     
         3 . An apparatus including a circuit for performing radio frequency identification (RFID), comprising:
 a plurality of RFID tags including a first set and a second set, wherein each of the plurality of RFID tags includes:
 an antenna, and 
 RFID electronics coupled to the antenna, 
   wherein the first set of the plurality of RFID tags is configured to activate in response to receiving an excitation signal, to generate a first plurality of responses as part of the excitation signal, to receive a first plurality of sleep commands as part of the excitation signal, and, in response to the first plurality of sleep commands, to decouple from an excitation field generated by the excitation signal,   wherein the second set of the plurality of RFID tags does not receive the excitation signal until the first set of the plurality of RFID tags has been decoupled from the excitation field, and   wherein the second set of the plurality of RFID tags is configured to activate in response to receiving the excitation signal, to generate a second plurality of responses as part of the excitation signal, to receive a second plurality of sleep commands as part of the excitation signal, and to decouple from an excitation field generated by the excitation signal, in response to the second plurality of sleep commands.   
     
     
         4 . An apparatus for performing radio frequency identification (RFID), comprising:
 an RFID reader that includes a reader antenna, wherein the RFID reader is configured to generate an excitation signal; and   a plurality of RFID tags including a first set and a second set, wherein each of the plurality of RFID tags includes:
 a tag antenna, and 
 RFID electronics coupled to the tag antenna, 
   wherein the first set of the plurality of RFID tags is configured to activate in response to receiving the excitation signal, and to generate a first plurality of responses as part of the excitation signal,   wherein the RFID reader is configured to decode the first plurality of responses from the excitation signal, and to transmit a first plurality of sleep commands to the first set of the plurality of RFID tags using the excitation signal,   wherein the first set of the plurality of RFID tags is configured to receive the first plurality of sleep commands as part of the excitation signal, and, in response to the first plurality of sleep commands, to decouple from an excitation field generated by the excitation signal,   wherein the second set of the plurality of RFID tags does not receive the excitation signal until the first set of the plurality of RFID tags has been decoupled from the excitation field,   wherein the second set of the plurality of RFID tags is configured to activate in response to receiving the excitation signal, to generate a second plurality of responses as part of the excitation signal,   wherein the RFID reader is configured to decode the second plurality of responses from the excitation signal, and to transmit a second plurality of sleep commands to the second set of the plurality of RFID tags using the excitation signal, and   wherein the second set of the plurality of RFID tags is configured to receive the second plurality of sleep commands as part of the excitation signal, and, in response to the second plurality of sleep commands, to decouple from the excitation field generated by the excitation signal.