Two stage radio frequency interference cancellation system and method

• US 8,977,223 B1
• Filed: 03/19/2013
• Issued: 03/10/2015
• Est. Priority Date: 08/07/2008
• Status: Active Grant

• Current Assignee: Hypres, Inc.
• Original Assignee: Hypres, Inc.
• Inventors: Gupta, Deepnarayan, Inamdar, Amol
• Primary Examiner(s): Nguyen, Duc M
• Application Number:
  US13/847,118
• Time in Patent Office: 721 Days
• Field of Search: 455/295, 455/296, 455/304, 455/305, 455310-312, 455/570
• US Class Current: 455/296
• CPC Class Codes: H04B 1/10 Means associated with receiver for limiting or suppressing noise or interference
• 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
• CPC Class Codes: H04B 7/15585 by interference cancellation
• CPC Class Codes: H04L 27/01 Equalisers baseband equalizers at the transmitter end H04L25/03343; in analogue transmission systems H04B3/04, H04B7/005

Abstract

A radio frequency receiver subject to a large in-band interferor employs active cancellation with coarse and at least one cancellation signals, each with a respective radio frequency combiner, in order to increase the effective dynamic range of the receiver for weak signals of interest. One or both can be digitally synthesized. This is particularly applicable for co-site interference, whereby the interfering transmit signal is directly accessible. A similar system and method may also be applied to external interferors such as those produced by deliberate or unintentional jamming signals, or by strong multipath signals. An adaptive algorithm may be used for dynamic delay and gain matching. In a preferred embodiment, a hybrid technology hybrid temperature system incorporates both superconducting and semiconducting components to achieve enhanced broadband performance.

Claims

1. An electromagnetic radiation receiving method, comprising:

generating at least one analog reference signal corresponding to a frequency and phase of at least one signal within an electromagnetic radiation band, the at least one analog reference signal being generated in dependence on a digital model of the at least one signal which is controlled for at least amplitude and delay;

combining a received waveform within the electromagnetic radiation band containing the at least one signal and a further signal modulated with information with the at least one corresponding analog reference signal in a first analog combiner to generate a first residue signal, at least the delay and magnitude being controlled such that a magnitude of the at least one signal within the first residue signal is reduced with respect to the received waveform and the further signal modulated with information is substantially undistorted;

generating at least one cancellation signal, selectively dependent on a residue of the at least one signal in the residue signal, controllable with respect to at least magnitude and delay based on a feedback input;

combining the first residue signal with the at least one cancellation signal in a second combiner to generate a second residue signal; and

generating the feedback input based on at least the second residue signal to control said generating the at least one cancellation signal with respect to at least magnitude, and delay, such that a magnitude of the at least one signal within the second residue signal is reduced with respect to the first residue signal; and

demodulating the information.

2. The method according to claim 1, wherein the at least one cancellation signal is an analog signal generated based on a second digital reference signal.

3. The method of claim 2, further comprising:

(a) digitally correlating the second residue signal with the second digital reference signal; and

(b) using a time-averaged digital correlation output to provide the feedback input as an adaptive feedback control of at least one of the magnitude and delay of the at least one cancellation signal.

4. The method of claim 3, further comprising applying an iterative algorithm to adjust at least one of the magnitude and delay of the at least one cancellation signal, in order to reduce the time-averaged digital correlation output toward zero.

5. The method of claim 1, wherein the digital model is provided by the source signal of the at least one signal.

6. The method of claim 5, wherein the at least one corresponding analog reference signal comprises a linear combination of plurality of representations of a signal having respectively different magnitudes and delays.

7. The method according to claim 1, wherein the at least one signal comprises a multipath interference signal, and wherein the at least one analog analog reference signal comprises a plurality of analog signals differing in respective magnitude and delay.

8. The method of claim 1, further comprising digitizing the second residue signal using a superconducting analog to digital converter.

9. The method of claim 1, wherein the at least one cancellation signal is generated based on a digital lookup table which is adaptively updated.

10. The method of claim 1, further comprising a limiter which limits a power of the first residue signal before it reaches the second combiner.

11. The method of claim 1, wherein a dynamic range of the second residue signal with respect to a lowest information carrying amplitude of the further signal modulated with information is reduced with respect to the received waveform.

12. The method of claim 1, wherein the second combiner comprises a superconducting transformer having at least three coils.

13. An electromagnetic radiation receiver, comprising:

at least one signal processor configured to generate at least one analog reference signal corresponding to at least one signal within an electromagnetic radiation band, wherein at least a delay and a magnitude of the at least one analog reference signal are digitally controllable in dependence on a digital model of the at least one signal;

a first analog combiner configured to combine a received waveform within the electromagnetic radiation band containing the at least one signal and an information carrier, with the at least one analog reference signal, to generate a first residue signal, at least the delay and magnitude of the at least one analog reference signal being controllable such that a magnitude of the at least one signal within the first residue signal is reduced with respect to the received waveform and the information carrier is substantially undistorted;

a second combiner configured to combine the first residue signal with at least one cancellation signal to generate a second residue signal; and

at least one digital processor configured to generate the at least one cancellation signal, corresponding to a residue of the at least one signal in the residue signal, controlled with respect to at least magnitude and delay based on a feedback input from the second residue signal, such that a magnitude of the at least one signal within the second residue signal is reduced with respect to the first residue signal and the information carrier is substantially undistorted.

14. The system of claim 13, further comprising:

(a) a digitizer configured to digitize the second residue signal;

(b) a digital correlator configured to correlate the digitized second residue signal with the second digital reference signal;

the at least one digital processor being further configured to receive an output of the digital correlator, and to adaptively adjust at least one of the magnitude and delay of the at least one cancellation signal.

15. The receiver of claim 14, wherein the at least one digital processor is further configured to perform an iterative algorithm to adjust at least one of the magnitude and delay of the at least one cancellation signal, in order to reduce toward zero a time-averaged digital output of the digital correlator.

16. The receiver according to claim 13, wherein the at least one signal comprises a multipath interference signal, and wherein the at least one digital processor generates at least one digital reference signal as a plurality of representations of a common digital reference signal differing in respective magnitude and delay.

17. The receiver of claim 13, further comprising a limiter configured to restrict at least a portion of a power of the first residue signal from the first analog combiner when the power of the first residue signal exceeds a threshold, wherein the first analog combiner comprises a superconducting transformer with at least three coils, and wherein the at least one digital processor comprises an adaptively updated a digital lookup table for generation of the at least one cancellation signal, wherein the digitizer comprises a superconducting analog to digital converter having a dynamic range, the dynamic range being insufficient to extract all information from the information carrier, wherein the magnitude and delay of the digital reference signal and the at least one cancellation signal are adjusted such that the dynamic range of the digitizer is sufficient to demodulate the information from the information carrier in the second residue signal.

18. A receiver, comprising:

(a) an input configured to receive an analog signal comprising an information carrier and at least one signal within an electromagnetic radiation band;

(b) a first combiner configured to combine the analog signal with a first signal to produce a first combined signal with a reduced power of the at least one signal with respect to the input, substantially without non-linear distortion of the information carrier;

(c) a second combiner configured to combine the first combined signal, received by the second combiner substantially without introduction of intermodulation products of the analog signal and the first signal, with a second signal to produce a second combined signal with a reduced power of the at least one signal with respect to the first combined signal, substantially without distortion of the information carrier;

(d) a digitizer, configured to digitize the second combined signal while substantially retaining information corresponding to the information carrier; and

(e) a feedback controlled signal generator, configured to receive a representation of the digitized second combined signal, and control a generation of at least one of the first signal and the second signal effective increase a magnitude ratio of the information carrier to the at least one signal in the second combined signal.

19. The receiver of claim 18, further comprising at least one superconducting device selected from the group consisting of a digital processor, a digital correlator, an analog to digital converter, and a transformer.

20. The receiver of claim 18, wherein the feedback controlled signal generator comprises a digital correlator which is configured to determine a characteristic delay of the at least one signal, and to control a delay of a component of the second signal with respect to the characteristic delay to the at least one signal.