System and technique for calibrating radar arrays

• US 20060132357A1
• Filed: 12/22/2004
• Published: 06/22/2006
• Est. Priority Date: 12/22/2004
• Status: Active Grant

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Dull, Wesley Thomas, Pozgay, Jerome Howard
• Granted Patent: US 7,183,969 B2
• Time in Patent Office: Days
• US Class Current: 342/174
• CPC Class Codes: G01S 13/003 Bistatic radar systems; Multistatic radar systems
• CPC Class Codes: G01S 13/723 by using numerical data
• CPC Class Codes: G01S 13/87 Combinations of radar systems, e.g. primary radar and secondary radar
• CPC Class Codes: G01S 7/4004 of parts of a radar system

Abstract

A system and technique for calibrating a plurality of radars provides a set of simultaneous equations derived from monostatic echo returns from a plurality of targets. A solution of the simultaneous equations provides relative position calibration factors and time delay calibration factors associated with the plurality of radars. The relative position calibration factors and the time delay calibration factors allow the plurality of radars to be coherently combined with only a small amount of processing gain loss compared with an ideal coherent processing gain.

Claims

1. A method of calibrating a plurality of radars, comprising;

selecting a reference radar from among the plurality of radars;

selecting one or more pairs of radars, each one of the pairs of radars including the reference radar and a respective paired radar from among the plurality of radars;

identifying at least three targets;

generating a first at least three target tracks associated with the at least three targets with the reference radar;

generating a second at least three target tracks associated with the at least three targets with the paired radar; and

relating the first at least three target tracks with the second at least three target tracks to provide a calibration indicative of a relative position and a relative time delay of the paired radar relative to the reference radar.

2. The method of claim 1, wherein the relating comprises:

generating a first equation associated with a first track point within a first one of the first at least three target tracks and associated with a first track point within a first one of the second at least three target tracks;

generating a second equation associated with a first track point within a second one of the first at least three target tracks and associated with a first track point within a second one of the second at least three target tracks;

generating a third equation associated with a first track point within a third one of the first at least three target tracks and associated with a first track point within a third one of the second at least three target tracks; and

solving at least the first, second and third equations simultaneously to provide the calibration indicative of the relative position of the paired radar relative to the reference radar.

3. The method of claim 2, further including:

solving at least the first, second and third equations simultaneously to provide the calibration indicative of the relative time delay of the paired radar relative to the reference radar, wherein the relative time delay is a total time delay including a sum of a relative transmit time delay and a relative receive delay.

4. The method of claim 2, further including:

solving at least the first, second and third equations simultaneously to provide the calibration indicative of the relative time delay of the paired radar relative to the reference radar, wherein the relative time delay includes a relative transmit time delay and a relative receive delay.

5. The method of claim 1, wherein the calibration is indicative of a relative position of the

paired radar relative to the reference radar in at least two dimensions.

6. The method of claim 1, wherein the calibration is indicative of a relative position of the paired radar relative to the reference radar in at least three dimensions.

7. The method of claim 1, wherein the relating the first at least three target tracks with the second at least three target tracks comprises relating a first respective track point within each of the first at least three target tracks with a corresponding first respective track point within each of the second at least three target tracks to provide a first calibration indicative of the relative position and the relative time delay of the paired radar relative to the reference radar.

8. The method of claim 7, further including:

relating a second respective track point within each of the first at least three target tracks with a corresponding second respective track point within each of the second at least three target tracks to provide a second calibration indicative of the relative position and the relative time delay of the paired radar relative to the reference radar; and

averaging the first calibration with at least the second calibration to provide an averaged calibration.

9. The method of claim 1, wherein the generating the first at least three target tracks comprises generating a respective monostatic target track associated with each of the at least three targets with the reference radar and the generating the second at least three target tracks comprises generating a respective monostatic target track associated with each of the at least three targets with the paired radar.

10. The method of claim 1, wherein the generating the first at least three target tracks comprises generating a respective monostatic target track and a respective bistatic target track associated with each of the at least three targets with the reference radar and the generating the second at least three target tracks comprises generating a respective monostatic target track and a respective bistatic target track associated with each of the at least three targets with the paired radar.

11. The method of claim 1, further including:

transmitting a first radar signal with the reference radar; and

transmitting a second radar signal with the paired radar, wherein the first radar signal is orthogonal to the second radar signal.

12. The method of claim 11, wherein the first radar signal and the second radar signal are transmitted concurrently.

13. The method of claim 1, wherein the selecting one or more pairs of radars results in each of the plurality of radars being included in a respective pair of radars.

14. The method of claim 1, wherein the at least three targets include a first, second, and third target and the generating the respective target track for each of the reference radar and the respective paired radar and for each of the at least three targets comprises:

transmitting a first radar signal with the reference radar toward the first target;

receiving a first monostatic target echo from the first target associated with the first radar signal with the reference radar;

transmitting a second radar signal with the paired radar toward the first target;

receiving a second monostatic target echo from the first target associated with the second radar signal with the paired radar;

generating a first track point for a first monostatic target track associated with the first monostatic target echo;

generating a first track point for a second monostatic target track associated with the second monostatic target echo;

transmitting a third radar signal with the reference radar toward the second target;

receiving a third monostatic target echo from the second target associated with the third radar signal with the reference radar;

transmitting a fourth radar signal with the paired radar toward the second target;

receiving a fourth monostatic target echo from the second target associated with the fourth radar signal with the paired radar;

generating a first track point associated with a third monostatic target track associated with the third monostatic target echo;

generating a first track point associated with a fourth monostatic target track associated with the fourth monostatic target echo;

transmitting a fifth radar signal with the reference radar toward the third target;

receiving a fifth monostatic target echo from the third target associated with the fifth radar signal with the reference radar;

transmitting a sixth radar signal with the paired radar toward the third target;

receiving a sixth monostatic target echo from the third target associated with the sixth radar signal with the paired radar;

generating a first track point associated with a fifth monostatic target track associated with the fifth monostatic target echo; and

generating a first track point associated with a sixth monostatic target track associated with the sixth monostatic target echo.

15. The method of claim 14, wherein the first radar signal is orthogonal to the second radar signal, the third radar signal is orthogonal to the fourth radar signal, and the fifth radar signal is orthogonal to the sixth radar signal.

16. The method of claim 14, wherein the first radar signal is transmitted concurrently with the second radar signal, the third radar signal is transmitted concurrently with the fourth radar signal, and the fifth radar signal is transmitted concurrently with the sixth radar signal.

17. The method of claim 14, further including:

receiving a first bistatic target echo from the first target associated with the first radar signal with the reference radar;

receiving a second bistatic target echo from the first target associated with the second radar signal with the paired radar;

generating a first track point for a first bistatic target track associated with the first bistatic target echo;

generating a first track point for a second bistatic target track associated with the second bistatic target echo;

receiving a third bistatic target echo from the second target associated with the third radar signal with the reference radar;

receiving a fourth bistatic target echo from the second target associated with the fourth radar signal with the paired radar;

generating a first track point associated with a third bistatic target track associated with the third bistatic target echo;

generating a first track point associated with a fourth bistatic target track associated with the fourth bistatic target echo;

receiving a fifth bistatic target echo from the third target associated with the fifth radar signal with the reference radar;

receiving a sixth bistatic target echo from the third target associated with the sixth radar signal with the paired radar;

generating a first track point associated with a fifth bistatic target track associated with the fifth bistatic target echo; and

generating a first track point associated with a sixth bistatic target track associated with the fourth bistatic target echo.

18. The method of claim 1, wherein the at least three targets include at least three calibration targets adapted to provide the calibration.

19. The method of claim 1, wherein the at least three targets include at least one calibration target adapted to provide the calibration.

20. The method of claim 1, wherein the at least three targets include at least one target of opportunity.

21. The method of claim 1, wherein at least two of the at least three targets are located at a relative azimuthal angle of at least twenty degrees within the field of view of each of the plurality of radars.

22. The method of claim 1, wherein at least two of the at least three targets are located at a relative azimuthal angle of at least fifty-five degrees within the field of view of each of the plurality of radars.

23. The method of claim 1, wherein at least three of the at least three targets are located at mutually relative angles of at least twenty degrees within the field of view of each of the plurality of radars.

24. The method of claim 1, wherein at least three of the at least three targets are located at mutually relative angles of at least fifty-five degrees within the field of view of each of the plurality of radars.

25. A system for calibration of a plurality of radars, comprising:

a reference radar to transmit a first radar signal;

a paired radar associated with the reference radar selected from among the plurality of radars to transmit a second radar signal;

a first radar track processor coupled to the reference radar to generate a first at least three target tracks;

a second radar track processor coupled to the paired radar to generate a second at least three target tracks;

a track relating processor coupled to the first and second track processors to relate the first at least three target tracks generated by the first track processor with the second at least three target tracks generated by the second track processor; and

a simultaneous equation processor coupled to the track relating processor and adapted to further relate the first at least three target tracks to the second at least three target tracks to provide a calibration indicative of a relative position and a relative time delay of the paired radar relative to the reference radar.

26. The system of claim 25, wherein the simultaneous equation processor is adapted to relate the first at least three target tracks to the second at least three target tracks to provide first and second calibrations, each indicative of the relative position and the relative time delay of the paired radar relative to the reference radar.

27. The system of claims 26, wherein the relative time delay is a total time delay including a sum of a relative transmit time delay and a relative receive delay.

28. The system of claims 26, wherein the relative time delay includes a relative transmit time delay and a relative receive delay.

29. The system of claim 26, further including an averaging processor coupled to the simultaneous equation processor to average the first and second calibrations to provide an averaged calibration.

30. The system of claim 29, further including a coherency processor coupled to the averaging processor, the first radar track processor, and the second radar track processor to relate the first at least three target tracks, the second at least three target tracks, and the averaged calibration to provide at least three cohered target tracks.

31. The system of claim 25, wherein the first radar signal is orthogonal to the second radar signal.

32. The system of claim 31, wherein the first radar signal is transmitted concurrently with the second radar signal.

33. The system of claim 25, further including at least three calibration targets, each calibration target associated with a respective one of the first at least three target tracks and with a respective one of the second at least three target tracks.