Noncoherent gain enhancement technique for non-stationary targets

• US 6,538,599 B1
• Filed: 11/16/2001
• Issued: 03/25/2003
• Est. Priority Date: 11/16/2001
• Status: Expired due to Term

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: David, George Thomas
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): ALSOMIRI, ISAM A
• Application Number:
  US09/992,459
• Time in Patent Office: 494 Days
• Field of Search: 342/93, 342/95, 342/96-97, 342/101, 342/106, 342/113, 342/115, 342/194-196, 342/159, 342/162
• US Class Current: 342/196
• CPC Class Codes: G01S 13/288 phase modulated
• CPC Class Codes: G01S 13/4463 using phased arrays
• CPC Class Codes: G01S 13/582 adapted for simultaneous range and velocity measurements
• CPC Class Codes: G01S 7/2926 by integration

Abstract

A radar system and radar processing method includes a number of aspects for providing improved function. The system and method may employ one or more of the following aspects: timely range-velocity (range-Doppler) compensation for target nonstationarity by integration along hypothesized range-Doppler trajectories, allowing noncoherent integration over an elongated time interval; noncoherent integration of an enlarged signal set obtained from overlapped coherent processing intervals (CPIs); hypothesized joint multiple accelerations used to generate multiple hypothesized range-Doppler trajectories; and sliding window integration to increase data output rates with use of large noncoherent integration intervals (NCIs). These aspects allow for improved signal-to-noise ratios, for acquisition and tracking of targets at longer ranges, and for improved target parameter estimation.

Claims

1. A method of processing data in a sensor system that receives signal returns from pulsed coherent transmitted signals, the method comprising:

forming a plurality of range-Doppler maps; and

noncoherently integrating the results of the range-Doppler maps along a hypothesized range-velocity trajectory that is a function of a hypothesized acceleration, thereby producing combined range-Doppler results.

2. The method of claim 1, wherein the hypothesized acceleration is a hypothesized target acceleration.

3. The method of claim 1, wherein the forming the range-Doppler maps includes:

range filtering the received signal returns to produce range-filtered data;

formatting the range-filtered data of a post detection integration interval into a plurality of data sequences;

performing Fast Fourier Transform (FFT) processing on the data sequences to provide transformed data sequences; and

producing the range-Doppler maps from the transformed data sequences.

4. The method of claim 3, wherein the formatting the range-filtered data includes formatting the data into a plurality of overlapping coherent processing interval (CPI) data sequences.

5. The method of claim 4, wherein the plurality of overlapping CPI data sequences are overlapped by a 50% overlap rate.

6. The method of claim 4, wherein the plurality of overlapping CPI data sequences are overlapped by a 75% overlap rate.

7. The method of claim 1, wherein the hypothesized range-velocity trajectory is also a function of a hypothesized velocity.

8. The method of claim 7, further comprising, prior to the noncoherently integrating, selecting the hypothesized initial velocity from one or more of the range-Doppler maps.

9. The method of claim 1, wherein the hypothesized range-velocity trajectory is also a function of a hypothesized initial range of the target object.

10. The method of claim 9, further comprising, prior to the noncoherently integrating, selecting the hypothesized initial range from one or more of the range-Doppler maps.

15. The method of claim 1, wherein the noncoherently integrating includes sliding window integrating, utilizing the range-Doppler maps in multiple integrations at multiple times.

16. The method of claim 1, wherein the hypothesized acceleration is a time-varying acceleration.

17. The method of claim 16, wherein the time-varying acceleration corresponds to a hypothesized target maneuver.

18. The method of claim 17, wherein the target maneuver includes a turning maneuver.

11. A method of processing data in a sensor system that received signal returns from pulsed coherent transmitted signals, the method comprising:

forming a plurality of range-Doppler maps; and

noncoherently integrating the results of the range-Doppler maps along a hypothesized range-velocity trajectory that is a function of a hypothesized acceleration, thereby producing combined range-Doppler results;

wherein the noncoherently integrating Includes multiple noncoherent integrations, using a variety of different hypothesized accelerations, and thereby producing a plurality of integrated results, and further comprising selecting among the plurality of the integrated results.

12. The method of claim 11, wherein the selecting includes selecting the integrated result that has the highest magnitude in a range-Doppler bin.

13. The method of claim 11, wherein the noncoherently integrating further includes selecting the hypothesized accelerations from a predetermined acceleration range.

14. The method of claim 13, wherein the acceleration range is bounded by a predetermined maximum acceleration.

29. The method of claim 11, wherein the hypothesized accelerations includes hypothesized target accelerations.

30. The method of claim 11, wherein the forming the range-Doppler maps includes:

range filtering the received signal returns to produce range-filtered data;

formatting the range-filtered da(a of a post detection integration interval into a plurality of data sequences;

performing Fast Fourier Transform (FFT) processing on the data sequences to provide transformed data sequences; and

producing the range-Doppler maps from the transformed data sequences.

31. The method of claim 30, wherein the formatting the range-filtered data includes formatting the data into a plurality of overlapping coherent processing interval (CPI) data sequences.

32. The method of claim 31, wherein the plurality of overlapping CPI data sequences are overlapped by a 50% overlap rate.

33. The method of claim 31, wherein the plurality of overlapping CPI data sequences are overlapped by a 75% overlap rate.

34. The method of claim 11, wherein the hypothesized range-velocity trajectory is also a function of a hypothesized velocity.

35. The method of claim 34, further comprising, prior to the noncoherently integrating, selecting the hypothesized initial velocity from one or more of the range-Doppler maps.

36. The method of claim 11, wherein the hypothesized range-velocity trajectory is also a function of a hypothesized initial range of the target object.

37. The method of claim 36, further comprising, prior to the noncoherently integrating, selecting the hypothesized initial range from one or more of the range-Doppler maps.

38. The method of claim 11, wherein the noncoherently integrating includes sliding window integrating, utilizing the range-Doppler maps in multiple integrations at multiple times.

39. The method of claim 11, wherein the hypothesized acceleration is a time-varying acceleration.

40. The method of claim 39, wherein the time-varying acceleration corresponds to a hypothesized target maneuver.

41. The method of claim 40, wherein the target maneuver includes a turning maneuver.

19. A method of processing data in a sensor system that receives signal returns from pulsed coherent transmitted signals, the method comprising:

generating range-Doppler data from the signal returns;

determining multiple hypothetical target range-velocity trajectories, wherein the trajectories utilize different hypothesized accelerations; and

noncoherently integrating the range-Doppler data along the multiple hypothesized range-velocity trajectories, thereby producing multiple combined range-Doppler results.

20. The method of claim 19, further comprising selecting among the multiple range-Doppler results.

21. The method of claim 20, wherein the selecting includes evaluating the range-Doppler results using a constant false alarm rate detection algorithm.

22. The method of claim 19, wherein the determining further includes selecting the hypothesized accelerations from a predetermined acceleration range.

23. The method of claim 22, wherein the acceleration range is bounded by a predetermined maximum acceleration.

24. The method of claim 19, wherein the noncoherently integrating includes sliding window integrating of the range-Doppler data in multiple integrations at multiple times.

25. The method of claim 19, wherein the hypothesized accelerations include time-varying accelerations.

26. The method of claim 25, wherein at least some of the time-varying accelerations correspond to one or more hypothesized target maneuvers.

27. The method of claim 26, wherein the one or more target maneuvers includes a turning maneuver.

28. A method of processing data in a sensor system that receives signal returns from pulsed coherent transmitted signals reflected by a target, the method comprising:

generating range-Doppler data from the signal returns;

determining multiple hypothetical target range-velocity trajectories;

noncoherently integrating the range-Doppler data along the multiple hypothesized range-velocity trajectories, thereby producing multiple combined range-Doppler results; and

selecting among the multiple range-Doppler results for providing information regarding the target;

wherein the trajectories utilize different hypothesized accelerations;

wherein the hypothesized accelerations include time-varying accelerations; and

wherein at least some of the time-varying accelerations correspond to one or more hypothesized target maneuvers of the target.