System and method for mitigating co-channel interference in passive coherent location applications

• US 6,703,968 B2
• Filed: 05/03/2002
• Issued: 03/09/2004
• Est. Priority Date: 05/04/2001
• Status: Active Grant

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Inventors: Baugh, Kevin W.
• Primary Examiner(s): Lobo, Ian J.
• Application Number:
  US10/137,646
• Publication Number:
  US 20020167440A1
• Time in Patent Office: 676 Days
• Field of Search: 342/55, 342/125, 342/453, 342/463, 342/464
• US Class Current: 342/125
• CPC Class Codes: G01S 13/003 Bistatic radar systems; Multistatic radar systems
• CPC Class Codes: G01S 13/878 Combination of several spaced transmitters or receivers of known location for determining the position of a transponder or a reflector G01S13/874 takes precedence
• CPC Class Codes: G01S 2013/0245 Radar with phased array antenna
• CPC Class Codes: G01S 7/023 Interference mitigation, e.g. reducing or avoiding non-intentional interference with other HF-transmitters, base station transmitters for mobile communication or other radar systems, e.g. using electro-magnetic interference [EMI] reduction techniques auxiliary means for detecting or identifying radar signals or the like G01S7/021; means for anti-jamming G01S7/36
• CPC Class Codes: G01S 7/0236 Avoidance by space multiplex
• CPC Class Codes: G01S 7/292 Extracting wanted echo-signals

Abstract

A system and method for mitigating co-channel interference is disclosed. A radar system detects targets from received signals at an antenna array. The received signals include direct signals and target signals transmitted from remote transmitters. An antenna array receives the signals. A signal processing system is coupled to the antenna array to perform processing operations on the received signals. The processing system includes a primary cancellation component and a secondary cancellation component. A primary illuminator signal is cancelled from the received signals by the primary cancellation component. An adaptive beam former obtains a secondary illuminator signal from the received signals. A reference regenerator regenerates the secondary illuminator signal. An adaptive cancellation filter removes noise from the secondary illuminator signal. The secondary cancellation component mitigates co-channel interference by canceling the secondary illuminator signal from the received signals.

Claims

1. A method for mitigating co-channel interference in co-channel signals in a bistatic radar, comprising:

identifying a primary illuminator signal from a primary illuminator, wherein said primary illuminator signal comprises a frequency modulated carrier at a given frequency;

regenerating said primary illuminator signal;

canceling said primary illuminator signal from said co-channel signals;

identifying a secondary illuminator signal from a secondary illuminator, wherein said secondary illuminator signal comprises a frequency modulated carrier at said given frequency;

regenerating said secondary illuminator signal; and

canceling said secondary illuminator signal from said co-channel signals.

2. The method of claim 1, further comprising performing adaptive beamforming to obtain said primary illuminator signal.

3. The method of claim 1, further comprising performing adaptive beamforming to obtain said secondary illuminator signal.

4. The method of claim 1, further comprising separating said primary illuminator signal and said secondary illuminator signal from said co-channel signals.

5. The method of claim 1, further comprising receiving said secondary illuminator signal over a greater distance than said primary illuminator signal.

6. The method of claim 1, further comprising receiving said co-channel signals at an antenna array coupled to said bi-static radar.

7. The method of claim 6, wherein said receiving includes receiving said co-channel signals transmitted from remote transmitters including said primary illuminator and said secondary illuminator.

8. The method of claim 6, further comprising transmitting signals as wideband signals from remote transmitters, wherein said signals correlate to said co-channel signals.

9. The method of claim 8, wherein said wideband signals are frequency-modulated broadcast signals.

10. The method of claim 8, wherein said wideband signals are high-definition television broadcast signals.

11. A method for mitigating co-channel interference in a bistatic radar receiving co-channel signals comprising target signals reflected by targets and direct signals transmitted by remote transmitters, comprising:

receiving said co-channel signals at an antenna coupled to said bi-static radar;

performing adaptive beamforming to obtain a primary illuminator reference signal from said direct signals and comprises a frequency modulated carrier at a given frequency;

regenerating said primary illuminator reference;

canceling said primary illuminator reference signal from said co-channel signals;

performing adaptive beamforming to obtain a secondary illuminator reference signal from said direct signals and comprises a frequency modulated carrier at said given frequency;

regenerating said secondary illuminator reference signal; and

canceling said secondary illuminator reference signal from said co-channel signals.

12. The method of claim 11, further comprising determining said primary illuminator reference signal is from a primary illuminator of said remote transmitters.

13. The method of claim 11, further comprising determining said secondary illuminator reference signal is from a secondary illuminator of said remote transmitters.

14. A system for mitigating co-channel interference in a bistatic radar system that detects targets from received signals at an antenna, wherein said received signals include direct signals transmitted from remote transmitters and target signals, the co-channel interference mitigation system comprising:

an antenna array to receive signals;

a primary cancellation component to cancel a primary illuminator reference signal from said received signals; and

a secondary cancellation component to cancel a secondary illuminator reference signal from said received signals, whereby, the secondary cancellation component comprises;

an adaptive beamformer to obtain a secondary illuminator signal from said received signals,

a reference regenerator to regenerate said secondary illuminator signal, and

an adaptive cancellation filter to mitigate co-channel interference by canceling said secondary illuminator signal.

15. The system of claim 14, wherein said primary illuminator reference signal and said secondary illuminator reference signal operate at a given frequency.

16. The system of claim 14, wherein said primary cancellation component includes a reference regenerator to obtain said primary illuminator reference signal.

17. The system of claim 16, wherein said primary cancellation component further includes an adaptive beamformer coupled to said antenna array and said reference regenerator.

18. The system of claim 14, wherein said primary cancellation component includes an adaptive cancellation filter.

19. The system of claim 14, wherein said primary illuminator reference signal is received from a primary illuminator and said secondary illuminator reference signal is received from a secondary illuminator.

20. The system of claim 19, wherein said secondary illuminator is located at a greater distance from said antenna array than said primary illuminator.

21. The system of claim 14, wherein said primary illuminator reference signal comprises a direct signal.

22. The system of claim 14, wherein said primary illuminator reference signal comprises a frequency-modulated broadcast signal.

23. The system of claim 14, wherein said primary illuminator reference signal comprises a high-definition television broadcast signal.

24. The system of claim 14, wherein said secondary illuminator reference signal comprises a direct signal.

25. The system of claim 14, wherein said secondary illuminator reference signal comprises a frequency-modulated broadcast signal.

26. The system of claim 14, wherein said secondary illuminator reference signal comprises a high-definition television broadcast signal.

27. A method for detecting targets by a bi-static radar system using transmitted signals from a plurality of remote transmitters, comprising:

receiving said transmitted signals and reflected signals from said targets;

converting said received signals into co-channel signals;

adaptive beamforming a secondary illuminator signal from said co-channel signals;

regenerating said secondary illuminator signal; and

canceling said secondary illuminator signal from said co-channel signals and mitigating co-channel interference.

28. The method of claim 27, further comprising canceling a primary illuminator signal from said co-channel signal, wherein said primary illuminator signal comprises the frequency of said secondary illuminator signal.

29. The method radar system of claim 28, wherein said secondary illuminator signal is a direct signal transmitted from a secondary illuminator.

30. A bistatic radar system that detects targets from received signals at an antenna, wherein said received signals include direct signals transmitted from remote transmitters and target signals, comprising:

an adaptive beamformer to obtain a secondary illuminator signal from said received signals;

a reference regenerator to regenerate said secondary illuminator signal; and

an adaptive cancellation filter to mitigate co-channel interference by canceling said secondary illuminator signal.

31. The bistatic radar system of claim 30, further comprising co-channel signals generated from said received signals, wherein said secondary illuminator signal is obtained from said co-channel signals.

32. The bistatic radar system of claim 30, further comprising a primary illuminator signal comprising the same frequency as said secondary illuminator signal, wherein said primary illuminator signal is cancelled from said received signals.