Systems and Methods to Use Radar in RFID Systems

{
  "publication_number": "US2012268308A1",
  "country": "US",
  "kind": "A1",
  "title": "Systems and Methods to Use Radar in RFID Systems",
  "abstract": "Systems and methods to use radar systems for radio frequency identification (RFID) applications. In one embodiment, radar systems are adapted to use RFID communications protocols and methods to enhance the usefulness of radar systems beyond the determination of the presence, distance, direction and/or speed of a vehicle or object, to additionally include the transmission of data such as object identification and additional messages or data.",
  "claims": [
    "1. A method of radio frequency identification (RFID), the method comprising: transmitting an electromagnetic wave from a radar transmitter toward an object having an RFID tag, the electromagnetic wave configured to allow a radar system to monitor at least one of distance, direction and speed of objects; modulating the electromagnetic wave reflected using the RFID tag according to data stored in the RFID tag; receiving the reflected electromagnetic wave using a radar receiver of the radar system to determine at least one of distance, direction and speed of the object; and extracting the data from the reflected electromagnetic wave received using the radar receiver. 2. The method of claim 1, further comprising: determining a range to the object using the reflected electromagnetic wave. 3. The method of claim 2, wherein the electromagnetic wave transmitted from the radar transmitter is a pulse of electromagnetic wave; and the RFID tag modulates the data on a plurality of separate pulses transmitted from the radar transmitter. 4. The method of claim 3, wherein the pulse of electromagnetic wave is modulated to achieve pulse compression in detecting the reflected electromagnetic wave. 5. The method of claim 1, wherein the RFID tag modulates the reflected electromagnetic wave through switching between a first state and a second state, wherein the RFID tag is more reflective in the second state than in the first state. 6. The method of claim 1, further comprising: modulating an electromagnetic wave to represent a command to the RFID tag; and transmitting the electromagnetic wave modulated with the command from the radar transmitter to the RFID tag; wherein the modulating of the electromagnetic wave reflected using the RFID tag according to the data stored in the RFID tag is in response to the command. 7. The method of claim 1, further comprising: determining a speed of the object using the reflected electromagnetic wave. 8. The method of claim 7, wherein the determining the speed of the object comprises determining a Doppler frequency shift in the reflected electromagnetic wave. 9. The method of claim 1, wherein the radar transmitter continuously transmitting the electromagnetic wave while the radar receiver receives reflected the electromagnetic wave; and the method further comprises: comparing the electromagnetic wave transmitted by the radar transmitter and the reflected electromagnetic wave received by the radar receiver to determine a round trip time of the reflected electromagnetic wave. 10. The method of claim 1, further comprising: transmitting a separate electromagnetic wave from the radar transmitter toward the object; receiving the separate electromagnetic wave reflected from the object using the radar receiver; and determining a range to the object or a rate of changing range to the object based on the separate electromagnetic wave reflected from the object and received using the radar receiver. 11. A radio frequency identification (RFID) system, comprising: an RFID tag; and a radar system having a radar transmitter, a radar receiver and an RFID reader circuit, the radar receiver to receive a radio frequency electromagnetic wave transmitted by the radar transmitter and reflected by the RFID tag, the RFID reader circuit to determine data transmitted by the RFID from the radio frequency electromagnetic wave received by the radar receiver, wherein the radio frequency electromagnetic wave transmitted by the radar transmitter is configured to allow the radar system to determine at least one of distance, direction and speed of objects. 12. The RFID system of claim 11, wherein the RFID tag is to modulate the radio frequency electromagnetic wave through changing from a first state to a second state according to the data; and the RFID tag is more reflective in the first state than in the second state. 13. The RFID system of claim 12, wherein the RFID tag modulates the radio frequency electromagnetic wave according to a predetermined characteristic of electromagnetic waves transmitted by the radar transmitter. 14. The RFID system of claim 13, wherein the characteristic includes a pulse repetition frequency. 15. The RFID system of claim 12, wherein the RFID tag has an antenna; and the antenna is connected to ground to be in the first state and disconnected from ground to be in the second state. 16. The RFID system of claim 11, wherein the radar system determines a position of the RFID tag based on a round trip time of the radio frequency electromagnetic wave. 17. The RFID system of claim 11, wherein the radar system determines a speed of the RFID tag based on a Doppler frequency shift in the radio frequency electromagnetic wave reflected by the RFID tag. 18. The RFID system of claim 11, wherein the radar transmitter is to transmit the radio frequency electromagnetic wave in a first mode to allow the RFID reader circuit to determine the data; and the radar transmitter is to transmit in a second mode to determine a range of the RFID tag. 19. A radio frequency identification (RFID) reader, comprising: a transmitter to transmit a radio frequency electromagnetic wave configured to allow a radar system to determine at least one of distance, direction and speed of objects; a receiver to receive the radio frequency electromagnetic wave reflected by an object; a radar circuit coupled with the transmitter and the receiver to identify at least a range or a speed of the object based on the radio frequency electromagnetic wave reflected by the object; and an RFID reader circuit coupled with the transmitter and the receiver to determine data transmitted by an RFID tag reflecting the radio frequency electromagnetic wave. 20. The RFID reader of claim 19, further comprising: a duplexer to couple the radar circuit to the transmitter and the receiver in a first mode and to couple the RFID reader circuit to the transmitter and the receiver in a second mode. 21. The RFID reader of claim 19, wherein the RFID reader circuit is to control the transmitter to modulate data on a radio frequency electromagnetic wave transmitted by the transmitter. 22. The RFID reader of claim 19, wherein the radar circuit is to identify at least a range or a speed of the object using the reflected radio frequency electromagnetic wave, while the RFID reader circuit determines the data using the reflected radio frequency electromagnetic wave. 23. The RFID reader of claim 19, wherein the receiver has a matched filter receiving an input signal generated according to the received radio frequency electromagnetic wave; and a pulse width of an output of the matched filter is smaller than a pulse width of the input. 24. A radio frequency identification (RFID) tag, comprising: an antenna; a transceiver coupled to the antenna to receive radar signals configured to allow a radar system to determine at least one of distance, direction and speed of objects and to modulate reflection of radar signals; and a controller coupled to the transceiver to modulate data on a plurality of separate pulses of radar signals. 25. The RFID tag of claim 24, wherein a predetermined number of bits of the data is modulated on each of the pulses. 26. The RFID tag of claim 25, wherein each of the pulses is modulated to transmit one bit of the data. 27. The RFID tag of claim 24, wherein the controller determines a pulse repetition frequency of the radar signals to modulate the data."
  ],
  "cpc": [
    "G01S 13/765",
    "G01S 13/282",
    "G01S 13/582",
    "G01S 2013/9316",
    "G01S 2013/9329"
  ],
  "assignees": [
    "TUTTLE JOHN R",
    "KEYSTONE TECHNOLOGY SOLUTIONS"
  ],
  "filing_date": "2008-06-05",
  "publication_date": "2012-10-25",
  "priority_date": "2008-06-05",
  "application_number": "US-13410608-A",
  "family_id": "47020893",
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}