Multi-level RF identification system

• US 6,765,476 B2
• Filed: 03/09/2001
• Issued: 07/20/2004
• Est. Priority Date: 03/09/2001
• Status: Expired due to Term

• Current Assignee: Battelle Memorial Institute
• Original Assignee: Battelle Memorial Institute
• Inventors: Anderson, Gordon A., Steele, Kerry D., Gilbert, Ronald W.
• Primary Examiner(s): Horabik, Michael
• Assistant Examiner(s): BANGACHON, WILLIAM L
• Application Number:
  US09/802,408
• Publication Number:
  US 20020158752A1
• Time in Patent Office: 1,229 Days
• Field of Search: 340/10.4, 340/10.42, 340/10.34, 340/825.72, 340/870.31, 340/384.7, 332/159, 332/102, 332/109, 332/160, 331/109, 331/183, 331/107.A, 329/359
• US Class Current: 340/10.4
• CPC Class Codes: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer

Abstract

A radio frequency identification system having a radio frequency transceiver for generating a continuous wave RF interrogation signal that impinges upon an RF identification tag. An oscillation circuit in the RF identification tag modulates the interrogation signal with a subcarrier of a predetermined frequency and modulates the frequency-modulated signal back to the transmitting interrogator. The interrogator recovers and analyzes the subcarrier signal and determines its frequency. The interrogator generates an output indicative of the frequency of the subcarrier frequency, thereby identifying the responding RFID tag as one of a “class” of RFID tags configured to respond with a subcarrier signal of a predetermined frequency.

Claims

1. A microwave radio frequency identification tag, comprising:

an antenna configured to receive a radio frequency signal;

a rectification circuit having a first input coupled to the antenna, a second input, and an output; and

a single-transistor R-C tag oscillator having an input coupled to the output of the rectification circuit and an output coupled to the second input of the rectification circuit, the tag oscillator being structured to modulate the radio frequency signal received at the antenna with a subcarrier signal-frequency signal and to apply the modulated radio frequency signal to the antenna configured to operate at microwave radio frequencies and formed on a silicon die.

2. The tag of claim 1, wherein the tag oscillator is activated by the radio frequency signal received at the antenna.

3. The tag of claim 1, wherein the tag oscillator is powered by the radio frequency signal received at the antenna.

4. The tag of claim 2, wherein the tag oscillator further comprises a uni-junction transistor oscillator.

5. A microwave radio-frequency identification system, comprising:

a radio frequency identification tag configured to operate at microwave radio frequencies and formed on a silicon die, comprising;

an antenna configured to receive a continuous wave radio frequency signal;

a rectification circuit having a first input coupled to the antenna, a second input, and an output; and

a single-transistor R-C tag oscillator having an input coupled to the output of the rectification circuit and an output coupled to the second input of the rectification circuit, the tag oscillator structured to modulate the radio frequency signal received at the antenna with a subcarrier single-frequency signal and to apply the modulated radio frequency signal to the antenna;

and further comprising an interrogator that includes;

a radio frequency oscillator configured to generate the continuous wave radio frequency signal;

an antenna coupled to the radio frequency oscillator; and

the means for recovering the subcarrier single-frequency signal generated by the tag oscillator from the modulated radio frequency signal.

6. A microwave radio frequency identification system, comprising:

a radio frequency identification tag configured to operate at microwave frequencies and formed on a silicon die, comprising;

an antenna configured to receive a continuous wave radio frequency signal;

a rectification circuit having a first input coupled to the antenna, a second input, and an output; and

a single-transistor R-C tag oscillator having an input coupled to the output of the rectification circuit and an output coupled to the second input of the rectification circuit, the tag oscillator structured to modulate the radio frequency signal received at the antenna with a subcarrier single-frequency signal and to apply the modulated radio frequency signal to the antenna;

and further comprising an interrogator that includes;

an antenna configured to transmit and receive continuous wave radio frequency signals;

a radio frequency oscillator configured to generate a continuous wave radio frequency signal and coupled to the antenna by a strip line;

a first terminal on the strip line phase shifted from a second terminal on the strip line by ninety degrees; and

a comparator coupled between the first and second terminals on the strip line.

7. A radio frequency identification system, comprising:

(a) a radio frequency transceiver including;

(i) a radio frequency oscillator generating a radio frequency interrogation signal,

(ii) an antenna coupled to the radio frequency oscillator, and

(iii) a detector coupled between the radio frequency oscillator and the antenna for recovering a subcarrier radio frequency signal from the interrogation signal; and

(b) an identification tag formed on a silicon die, including;

(i) a radio frequency antenna configured to receive the radio frequency interrogation signal,

(ii) a rectifier having a first input coupled to the radio frequency antenna, a second input, and an output, and

(iii) at least one single-transistor R-C tag oscillator having an input coupled to the output of the rectifier and an output coupled to the second input of the rectifier, the tag oscillator generating a single-frequency output signal for frequency modulating the radio frequency interrogation signal with at least one subcarrier radio frequency signal configured to operate at microwave radio frequencies and formed on a silicon die.

8. The radio frequency identification system of claim 7, wherein the at least one tag oscillator is further configured to generate the output signal in response to the radio frequency interrogation signal received at the radio frequency antenna.

9. The radio frequency identification system of claim 7, wherein the rectifier is further configured to transform energy in the radio frequency interrogation signal received at the radio frequency antenna to power the tag oscillator.

10. The radio frequency identification system of claim 7, wherein the radio frequency transceiver further comprises a processor coupled to an output of the detector and configured to sample the recovered subcarrier radio frequency signal and determine a frequency of the recovered subcarrier radio frequency signal.

11. The radio frequency identification system of claim 10, wherein the processor is further configured to output a signal indicative of the frequency of the recovered subcarrier radio frequency signal.

12. The radio frequency identification system of claim 7, wherein the tag oscillator further comprises a plurality of single-transistor oscillator.

13. The radio frequency identification system of claim 7, wherein the tag oscillator further comprises a uni-junction transistor as the single transistor R-C tag oscillator.

14. A method for performing radio frequency identification, the method comprising:

generating a microwave radio frequency interrogation signal;

detecting the radio frequency interrogation signal in a radio frequency identification tag;

responsively detecting the radio frequency interrogation signal and frequency modulating the radio frequency interrogation signal in the radio frequency identification tag with a subcarrier signal-frequency signal using at least one single-transistor R-C oscillator formed on a silicon die; and

returning the modulated radio frequency interrogation signal.

15. The method of claim 14, wherein the generating a radio frequency interrogation signal further comprises generating a continuous wave radio frequency interrogation signal.

16. The method of claim 14, wherein frequency modulating the radio frequency interrogation signal comprises generating a frequency modulating signal in the radio frequency identification tag that further comprises operating the oscillator in the radio frequency identification tag, and the sending modulated radio frequency interrogation signal further comprises applying the modulated radio frequency interrogation signal to an antenna portion of the radio frequency identification tag.

17. The method of claim 16, wherein the oscillator in the radio frequency identification tag further comprises a plurality of single-transistor oscillators.

18. The method of claim 14, further comprising detecting the transmitted modulated radio frequency interrogation signal in an interrogator generating the radio frequency interrogation signal.

19. The method of claim 18, further comprising recovering the subcarrier single-frequency signal from the modulated radio frequency interrogation signal.

20. The method of claim 19, further comprising determining a frequency of the recovered subcarrier single-frequency signal.

21. The method of claim 20, further comprising generating in the interrogator a signal indicative of the frequency of the recovered subcarrier single-frequency signal.