Adaptive coherent RFID reader carrier cancellation

• US 20060183454A1
• Filed: 04/04/2005
• Published: 08/17/2006
• Est. Priority Date: 02/14/2005
• Status: Active Grant

• Current Assignee: Zest Labs, Inc.
• Original Assignee: Intelleflex Corporation
• Inventors: Al-Mahdawi, Tareef Ibrahim
• Granted Patent: US 7,526,266 B2
• Time in Patent Office: Days
• US Class Current: 455/296
• CPC Class Codes: G06K 7/10346 the antenna being of the far field type, e.g. HF types or dipoles
• CPC Class Codes: H04B 1/109 by improving strong signal performance of the receiver when strong unwanted signals are present at the receiver input
• CPC Class Codes: H04B 1/525 with means for reducing leakage of transmitter signal into the receiver

Abstract

Systems and methods for adaptive cancellation of carrier content includes receiving a signal, adaptively detecting an amount of carrier content in the received signal, generating a feedback signal for canceling out the carrier content in the incoming signal, and introducing the feedback signal for canceling out a majority of carrier content in the signal being received

Claims

1. A method for adaptive cancellation of carrier content, comprising:

receiving a signal;

adaptively detecting an amount of carrier content in the received signal;

generating a feedback signal for canceling out the carrier content in the incoming signal; and

introducing the feedback signal for canceling out a majority of carrier content in the signal being received.

2. The method of claim 1, wherein the carrier content includes a reader carrier signal and phase noise associated with the reader carrier signal.

3. The method of claim 1, wherein the feedback signal is derived in part from an outgoing carrier signal.

4. The method of claim 1, wherein detecting an amount of carrier content in the received signal includes performing I-Q detection on the received signal.

5. The method of claim 1, wherein the method is performed by a radio frequency identification (RFID) reader.

6. The method of claim 1, wherein the feedback signal is an analog signal.

7. The method of claim 1, wherein the feedback signal is an analog fraction of an outgoing carrier signal.

8. The method of claim 1, wherein the signal being received is amplified by an amplifier, wherein the feedback signal is introduced to the signal being received at a point prior to the amplifier.

9. The method of claim 1, wherein automatic gain control is performed on the signal being received, wherein the feedback signal is introduced to the signal being received prior to performing automatic gain control thereon.

10. The method of claim 1, wherein downconversion is performed on the signal being received, wherein the feedback signal is introduced to the signal being received prior to performing downconversion thereon.

11. A system for adaptive cancellation of carrier content, comprising:

an antenna for receiving a signal;

a mechanism for adaptively detecting the amplitude of the carrier content in the received signal;

a mechanism for generating a feedback signal for canceling carrier content from the signal being received, the feedback signal being generated based at least in part on the detected amplitude of the carrier content in the received signal.

12. The system of claim 11, wherein the vector multiplier also receives a portion of an outgoing carrier signal, wherein the feedback signal is generated based at least in part on the portion of the outgoing carrier signal.

13. The system of claim 11, wherein the carrier content includes a reader carrier signal and phase noise associated with the reader carrier signal.

14. The system of claim 11, wherein the phase of the carrier content is also detected, wherein the feedback signal is generated based at least in part on the phase of the carrier content.

15. The system of claim 11, wherein the mechanism for adaptively detecting the amplitude of the carrier content includes a processor running a cancellation algorithm.

16. The system of claim 11, wherein the mechanism for generating the feedback signal includes a vector multiplier.

17. The system of claim 11, wherein the mechanism for adaptively detecting the amplitude of the carrier content and the mechanism for generating the feedback signal form part of a closed loop.

18. The system of claim 11, wherein the feedback signal is an analog signal.

19. The system of claim 11, wherein the feedback signal is combined with the signal being received.

20. The system of claim 11, further comprising an analog device for combining the feedback signal with the signal being received.

21. The system of claim 11, wherein the system is embodied in a radio frequency identification (RFID) reader.

22. A method for adaptive cancellation of carrier content, comprising:

receiving an incoming signal comprising a backscatter signal, the backscatter signal including a data signal from a remote device, a reader carrier signal, and phase noise associated with the reader carrier signal;

analyzing the backscatter signal; and

canceling a majority of the reader carrier signal and the phase noise associated with the carrier signal from the incoming signal based in part on the analysis of the backscatter signal.

23. The method of claim 22, wherein the reader carrier signal and associated phase noise is canceled by introducing a second signal derived in part from the reader carrier signal.

24. The method of claim 23, wherein the second signal is a replica of the reader carrier signal and phase noise associated therewith.

25. The method of claim 23, wherein the second signal is an analog signal, wherein the analog signal is combined with the incoming signal.

26. The method of claim 22, wherein the reader carrier signal and associated phase noise is cancelled by generating a feedback signal derived in part from an outgoing carrier signal and in part from the incoming reader carrier signal and phase noise associated therewith.

27. The method of claim 22, wherein the method is performed by a radio frequency identification (RFID) reader.

28. A method for adaptive cancellation of carrier content in a feedback loop with variable response times, comprising:

at a first speed defined by a response time of the feedback loop;

outputting a carrier signal;

receiving an incoming signal;

generating a feedback signal for canceling out carrier content from the incoming signal; and

feeding the feedback signal back into the incoming signal;

at a second speed slower than the first speed;

receiving the incoming signal;

detecting variations in the carrier content of the incoming signal;

continuously adjusting the feedback signal based on the variations in the carrier content in the incoming signal for canceling the carrier content in the incoming signal.

29. The method of claim 28, wherein the carrier content includes the carrier signal and phase noise associated with the carrier signal.

30. The method of claim 28, further comprising feeding a portion of the outgoing carrier signal into the incoming signal during processing of the incoming signal at the first speed.

31. The method of claim 28, wherein the detecting variations in the carrier content includes identifying a Doppler frequency shift characteristic of the carrier content.

32. The method of claim 28, wherein the method is repeated each time a frequency is changed.

33. The method of claim 28, wherein the second speed portion of the method is performed when the incoming signal includes a desired signal.

34. The method of claim 33, wherein the desired signal is a response from a remote device responding to the carrier signal.

35. The method of claim 34, wherein the remote device is a backscattering RFID tag.

36. The method of claim 28, wherein the second speed portion of the method begins after the carrier signal instructs RFID tags to respond to the carrier signal.

37. The method of claim 28, further comprising freezing the feedback loop during modulation of the outputted carrier signal.

38. The method of claim 28, wherein the method is performed by a radio frequency identification (RFID) reader.

39. A system for adaptive cancellation of carrier content, comprising:

an input for receiving an incoming signal from an antenna; and

an analog mechanism for subtracting a carrier signal and its associate phase noise from the incoming signal at the input.

40. The system of claim 39, further comprising a transmitter for transmitting an outgoing signal, wherein the system has an active mode and a suspended mode, operation of the analog mechanism being suspended in the suspended mode, wherein the suspended mode is invoked during modulation by the transmitter.

41. The system of claim 39, wherein the system is embodied in a radio frequency identification (RFID) reader.