Backscatter transponder interrogation device

• US 6,611,224 B1
• Filed: 05/14/2002
• Issued: 08/26/2003
• Est. Priority Date: 08/18/1997
• Status: Expired due to Fees

• Current Assignee: X-Cyte Inc.
• Original Assignee: X-Cyte Inc.
• Inventors: Skeie, Halvor, Nysen, Paul A.
• Primary Examiner(s): Gregory, Bernarr E.
• Application Number:
  US10/145,646
• Time in Patent Office: 469 Days
• Field of Search: 342/42-51, 342/175, 342/192, 342/193-197, 342/36-41, 342/82-103, 340/10-- 1, 340/505
• US Class Current: 342/42
• CPC Class Codes: G01S 13/343 using sawtooth modulation
• CPC Class Codes: G01S 13/755 using delay lines, e.g. acoustic delay lines
• CPC Class Codes: G06K 19/0672 with resonating marks
• CPC Class Codes: G06K 19/0675 the resonating marks being of the surface acoustic wave [SAW] kind SAW devices per se H03H9/64
• 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
• CPC Class Codes: H03H 9/02795 Multi-strip couplers as track changers
• CPC Class Codes: H03H 9/44 Frequency dependent delay lines, e.g. dispersive delay lines
• CPC Class Codes: H03H 9/6406 Filters characterised by a particular frequency characteristic

Abstract

A backscatter transponder interrogator, comprising a transmitter, emitting an interrogation signal for interacting with a backscatter transponder within an interrogation field, a plurality of antennas, each having a different and complementary property, such that a backscatter response from a backscatter transponder is likely to be preferentially received by at least one of said at least two antennas, a receiver, selecting an output from a selected antenna, and demodulating the backscatter response to produce an information signal, and a digitally controlled oscillator, producing an output controlling said transmitter and employed by said receiver to demodulate the backscatter response. The interrogator may have a plurality of transmit antennas. The antennas may have respectively different polarization properties, e.g., horizontal and vertical polarization. The interrogator may implement null steered polarization cancellation to distinguish between backscatter transponders within the interrogation field.

Claims

1. A backscatter transponder interrogator, comprising:

(a) a transmitter, emitting an interrogation signal for interacting with a backscatter transponder within an interrogation field;

(b) at least two antennas, each having a different and complementary property, such that a backscatter response from a backscatter transponder is likely to be preferentially received by at least one of said at least two antennas;

(c) a receiver, selecting an output from a selected antenna, and demodulating the backscatter response to produce an information signal; and

(d) a digitally controlled oscillator, producing an output controlling said transmitter and employed by said receiver to demodulate the backscatter response.

2. The interrogator according to claim 1, further comprising a control for selecting a subset of said at least two antennas to receive a signal to be demodulated by said receiver.

3. The interrogator according to claim 1, further comprising at least two transmit antennas, each having a different and complementary property, such that a backscatter transponder is likely to be preferentially excited by at least one of said at least two transmit antennas.

4. The interrogator according to claim 3, further comprising a control for selecting a subset of said at least two transmit antennas to receive a signal to be emitted by said transmitter.

5. The interrogator according to claim 1, wherein said at least two antennas differ in polarization property.

6. The interrogator according to claim 1, wherein a first antenna is horizontally polarized and a second antenna is vertically polarized.

7. The interrogator according to claim 1, wherein said receiver is a heterodyne receiver, said interrogator comprising a signal generator and at least two mixers, for extracting the backscatter response from the backscatter signal via an intermediate frequency.

8. The interrogator according to claim 1, further comprising an analog to digital converter for digitizing the backscatter response while preserving amplitude and phase response information.

9. The interrogator according to claim 1, wherein the backscatter response represents a phase-amplitude modulated signal.

10. The interrogator according to claim 1, wherein the backscatter response is produced by a surface acoustic wave device.

11. The interrogator according to claim 1, wherein an information signal is a modulated on said interrogation signal.

12. The interrogator according to claim 1, wherein the backscatter response is produced by an active backscatter tag.

13. The interrogator according to claim 12, wherein the active backscatter tag produces a backscatter response modulated using a quadrature amplitude modulation scheme.

14. The interrogator according to claim 1, wherein said receiver comprises a phase locked oscillator generating quadrature outputs, and a pair of mixers, each receiving a separate phase of said quadrature outputs.

15. The interrogator according to claim 1, wherein said receiver~comprises a matched filter for extracting information from the demodulated backscatter response.

16. The interrogator according to claim 1, wherein said receiver comprises a clock and data recovery subsystem.

17. The interrogator according to claim 1, wherein said receiver is responsive to demodulate the backscatter response from a backscatter transponder having a backscatter response having at least three sequential modulations of said interrogation signal, each of said sequential modulations conveying at least 4 bits of information and being separated by a time gap.

18. The interrogator according to claim 1, wherein said transmitter emits an interrogation signal which varies in frequency, phase and/or amplitude over time.

19. The interrogator according to claim 1, wherein said interrogation signal is a spread spectrum signal.

20. The interrogator according to claim 19, wherein said digitally controlled oscillator generates a spread spectrum output.

21. The interrogator according to claim 1, wherein the backscatter response is modulated on a spread spectrum carrier, said receiver correlating a received response with a representation of said spread spectrum carrier to demodulate the backscatter response.

22. The interrogator according to claim 1, wherein said interrogator is adapted to perform null steered polarization cancellation to differentiate between two backscatter transponders within the interrogation field.