Radar system and method

• US 6,650,272 B2
• Filed: 01/16/2002
• Issued: 11/18/2003
• Est. Priority Date: 01/16/2002
• Status: Expired due to Fees

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Rosen, Robert A., Krikorian, Kapriel V.
• Primary Examiner(s): Sotomayor, John B.
• Application Number:
  US10/050,481
• Publication Number:
  US 20030132874A1
• Time in Patent Office: 671 Days
• Field of Search: 342/25, 342/73, 342/82, 342/83, 342/88, 342/109, 342/111, 342/159, 342/162, 342/191, 342/192, 342/194, 342/195, 342/196
• US Class Current: 342/25.00R
• CPC Class Codes: G01S 13/524 based upon the phase or frequency shift resulting from movement of objects, with reference to the transmitted signals, e.g. coherent MTi
• CPC Class Codes: G01S 13/89 for mapping or imaging
• CPC Class Codes: G01S 7/292 Extracting wanted echo-signals

Abstract

A method for exciting an antenna with a waveform having a burst width and pulse width scaled proportionately with a selected range scale and a temporal filter to address any ambiguities in range resulting from the transmission of a signal in accordance with the novel waveform. The inventive filtering method includes the step of scanning a beam including a plurality of pulses of electromagnetic energy. The step of scanning the beam includes the step of outputting a beam excited by a waveform having a burst width and pulse width scaled proportionately with a selected range scale. Reflections of these pulses are received as return signals. The returns are processed to extract range in range rate measurements. The range and range rate measurements are compressed to form a plurality of range bins. The pulses are selectively weighted to reduce sidelobes resulting from a subsequent Fast Fourier transform (FFT) operation. The FFT operation is then performed for a predetermined number of pulses in at least one of the range bins at at least one frequency. A second FFT operation is then performed for pixels of azimuth data across the range bins. Finally, ambiguity nulling weights are provided and applied to each pixel of data in each range bin.

Claims

1. A data-processing system adapted for use with a system for scanning a beam including a plurality of pulses of electromagnetic energy, receiving reflections of the pulses in the beam as return signals, processing the return signals to extract range and range rate measurements, processing the range and range rate measurements to form a plurality of range bins, and selecting and weighting return pulses in the range bins, the data-processing system comprising:

first means for performing a Fast Fourier Transform for a predetermined number of pulses in at least one of the range bins at at least one frequency;

second means for performing a Fast Fourier Transform for pixels of azimuth data across the range bins; and

third means for applying ambiguity nulling weights to each pixel of data in each range bin.

2. The invention of claim 1 wherein the third means includes means for applying nulling weights to each pixel of data in each range bin based on beam scan geometry.

3. The invention of claim 1 wherein the third means includes means for applying nulling weights to each pixel of data in each range bin based on scan history.

4. The invention of claim 1 wherein the third means includes means for applying nulling weights to each pixel of data in each range bin based on range.

5. The invention of claim 1 wherein the third means includes means for applying nulling weights to each pixel of data in each range bin based on range ambiguity.

6. The invention of claim 1 wherein the third means includes means for applying nulling weights to each pixel of data in each range bin based on Doppler ambiguity.

7. The invention of claim 6 wherein the third means includes means for applying nulling weights to each pixel of data in each range bin based on pulse repetition frequency.

8. The invention of claim 1 wherein the third means includes means for applying nulling weights to each pixel of data in each range bin at each of a plurality of predetermined frequencies.

9. The invention of claim 8 further including fourth means for performing pulse detection integration across each of the frequencies of the beam.

10. A system comprising:

first means for scanning a beam including a plurality of pulses of electromagnetic energy;

second means for receiving reflections of the pulses in the beam as return signals;

third means for processing the return signals to extract range and range rate measurements therefrom;

fourth means for processing the range and range rate measurements to form a plurality of range bins;

fifth means for selecting and weighting return pulses in the range bins;

sixth means for performing a Fast Fourier Transform for a predetermined number of pulses in at least one of the range bins at at least one frequency;

seventh means for performing a Fast Fourier Transform for pixels of azimuth data across the range bins; and

eighth means for applying nulling weights to each pixel of data in each range bin.

11. The invention of claim 10 wherein the beam is a radar beam.

12. The invention of claim 10 wherein said first means includes means for outputting a beam excited by a waveform having a burst width and pulse width scaled proportionately with a selected range scale.

13. The invention of claim 10 wherein the fifth means for selecting and weighting return pulses in the range bins includes means for selecting and weighting the return pulses to reduce sidelobes resulting from the Fast Fourier transform of the predetermined number of pulses.

14. The invention of claim 10 wherein the fifth means includes means for selecting the pulses based on antenna scan weight.

15. The invention of claim 10 wherein the fifth means includes means for selecting the pulses based on a pulse repetition frequency of the pulses.

16. The invention of claim 10 wherein the seventh means includes means for selecting Fast Fourier Transform weighting windows.

17. The invention of claim 10 wherein the seventh means further includes means for performing a fast Fourier transform for pixels of azimuth data across the range bins based on scan geometry.

18. The invention of claim 17 wherein the seventh means further includes means for performing a fast Fourier transform for pixels of azimuth data across the range bins based on a scan history of the beam.

19. The invention of claim 10 wherein the eighth means includes means for applying nulling weights to each pixel of data in each range bin based on beam scan geometry.

20. The invention of claim 10 wherein the eighth means includes means for applying nulling weights to each pixel of data in each range bin based on scan history.

21. The invention of claim 10 wherein the eighth means includes means for applying nulling weights to each pixel of data in each range bin based on range.

22. The invention of claim 10 wherein the eighth means includes means for applying nulling weights to each pixel of data in each range bin based on range ambiguity.

23. The invention of claim 10 wherein the eighth means includes means for applying nulling weights to each pixel of data in each range bin based on Doppler ambiguity.

24. The invention of claim 23 wherein the eighth means includes means for applying nulling weights to each pixel of data in each range bin based on pulse repetition frequency.

25. The invention of claim 10 wherein the eighth means includes means for applying nulling weights to each pixel of data in each range bin at each of a plurality of predetermined frequencies.

26. The invention of claim 25 further including ninth means for performing pulse detection integration across each of the frequencies of the beam.

27. A method including the steps of:

scanning a beam including a plurality of pulses of electromagnetic energy;

receiving reflections of the pulses in the beam as return signals;

processing the return signals to extract range and range rate measurements therefrom;

processing the range and range rate measurements to form a plurality of range bins;

selecting and weighting return pulses in the range bins;

performing a Fast Fourier Transform for a predetermined number of pulses in at least one of the range bins at at least one frequency;

performing a Fast Fourier Transform for pixels of azimuth data across the range bins; and

applying nulling weights to each pixel of data in each range bin.

28. The invention of claim 27 wherein the step of scanning the beam includes the step of outputting a beam excited by a waveform having a burst width and pulse width scaled proportionately with a selected range scale.

29. The invention of claim 27 wherein the step of selecting and weighting return pulses in the range bins includes the step of selecting and weighting the return pulses to reduce sidelobes resulting from the Fast Fourier transform of the predetermined number of pulses.

30. The invention of claim 27 wherein the step of selecting and weighting return pulses in the range bins includes the step of selecting the pulses based on antenna scan weight.

31. The invention of claim 27 wherein the step of selecting and weighting return pulses in the range bins includes the step of selecting the pulses based on a pulse repetition frequency of the pulses.

32. The invention of claim 27 wherein the step of performing a Fast Fourier Transform for pixels of azimuth data across the range bins includes the step of selecting Fast Fourier Transform weighting windows.

33. The invention of claim 27 wherein the step of performing a Fast Fourier Transform for pixels of azimuth data across the range bins further includes the step of performing a fast Fourier transform for pixels of azimuth data across the range bins based on scan geometry.

34. The invention of claim 33 wherein the step of performing a Fast Fourier Transform for pixels of azimuth data across the range bins further includes the step of performing a fast Fourier transform for pixels of azimuth data across the range bins based on a scan history of the beam.

35. The invention of claim 27 wherein the step of applying nulling weights to each pixel of data in each range bin includes the step of applying nulling weights to each pixel of data in each range bin based on beam scan geometry.

36. The invention of claim 27 wherein the step of applying nulling weights to each pixel of data in each range bin includes the step of applying nulling weights to each pixel of data in each range bin based on scan history.

37. The invention of claim 27 wherein the step of applying nulling weights to each pixel of data in each range bin includes the step of applying nulling weights to each pixel of data in each range bin based on range.

38. The invention of claim 27 wherein the step of applying nulling weights to each pixel of data in each range bin includes the step of applying nulling weights to each pixel of data in each range bin based on range ambiguity.

39. The invention of claim 27 wherein the step of applying nulling weights to each pixel of data in each range bin includes the step of applying nulling weights to each pixel of data in each range bin based on Doppler ambiguity.

40. The invention of claim 39 wherein the step of applying nulling weights to each pixel of data in each range bin includes the step of applying nulling weights to each pixel of data in each range bin based on pulse repetition frequency.

41. The invention of claim 27 wherein the step of applying nulling weights to each pixel of data in each range bin includes the step of applying nulling weights to each pixel of data in each range bin at each of a plurality of predetermined frequencies.

42. The invention of claim 41 further including the step of performing pulse detection integration across each of the frequencies of the beam.