Single transmit multi-receiver modulation radar, multi-modulation receiver and method

• US 7,277,046 B2
• Filed: 07/08/2005
• Issued: 10/02/2007
• Est. Priority Date: 07/08/2005
• Status: Active Grant

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Dwelly, Wesley, Adams, Vinh
• Primary Examiner(s): Sotomayor; John B
• Application Number:
  US11/177,712
• Publication Number:
  US 20070018884A1
• Time in Patent Office: 816 Days
• Field of Search: 342/147, 342/189, 342/126, 342/133, 342/139, 342/140, 342/146, 342/56, 342417-419, 342/443, 342/444, 342/450, 342463-465
• US Class Current: 342/147
• CPC Class Codes: G01S 13/003 Bistatic radar systems; Multistatic radar systems
• CPC Class Codes: G01S 13/325 using transmission of coded signals, e.g. P.S.K. signals
• CPC Class Codes: G01S 13/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S13/46
• CPC Class Codes: G01S 3/30 derived directly from separate directional systems
• CPC Class Codes: G01S 7/35 Details of non-pulse systems

Abstract

A single transmit multi-receiver modulation radar modulates radar return signals received through an associated receive-signal path with one of a plurality of differing modulation waveforms having low-cross correlation products. Each receive-signal path may be associated with a different receive direction. The differently modulated return signals from each receive-signal path may be combined and correlations may be performed on the combined and differently modulated radar return signals using the modulation waveforms to locate a target. In some embodiments, the trajectory of the target may be extrapolated and the target'"'"'s source location may be determined.

Claims

1. A receiver comprising:

a plurality of modulators, each modulator to modulate signals received through an associated receive-signal path with one of a plurality of differing modulation waveforms having a low-cross correlation product;

combining circuitry to combine the modulated signals from each receive-signal path; and

signal processing circuitry to perform correlations on the modulated combined signals using the modulation waveforms.

2. The receiver of claim 1 wherein the modulation waveforms comprise a plurality of substantially-orthogonal waveforms.

3. The receiver of claim 1 wherein the modulation waveforms comprise a family of pseudo-orthogonal waveforms generated from pseudo-orthogonal codes.

4. The receiver of claim 3 wherein the modulators comprise phase modulators to phase-modulate signals received through the associated receive-signal path with one of the pseudo-orthogonal waveforms.

5. The receiver of claim 4 wherein a dot product of any two of the pseudo-orthogonal codes used to generate the family of pseudo-orthogonal waveforms is substantially zero.

6. The receiver of claim 4 wherein the phase modulators comprise bi-phase modulators to phase modulate signals received through the associated receive-signal path with a phase of either zero degrees or one-hundred eighty degrees in accordance with ones and zeros of one of the pseudo-orthogonal codes.

7. The receiver of claim 1 wherein the modulators comprise polyphase modulators, and

wherein the modulation waveforms are generated from a series of phase states of a quadratic polyphase waveform, wherein each modulator applies one of the phase states to received signals of the associated receive-signal path.

8. The receiver of claim 7 wherein the polyphase modulators modulate the received signals with a quadratic phase code associated with the quadratic polyphase waveform.

9. The receiver of claim 1 wherein the modulators comprise amplitude modulators to amplitude-modulate the signals received through each receive-signal path with a differing waveform.

10. The receiver of claim 1 wherein the modulators comprise pulse-position modulators to pulse-position modulate signals received through the associated receive-signal path with the substantially orthogonal pulse-position waveforms.

11. The receiver of claim 1 wherein each receive-signal path receives signals from an associated one of a plurality of spatially-separated antennas, the antennas positioned to receive signals from at least slightly different directions.

12. The receiver of claim 11 wherein the antennas are positioned circumferentially to receive signals over about a 360 degree detection zone in azimuth and a detection angle of up to about 60 degrees in elevation.

13. The receiver of claim 11 wherein the signals received through the receive-signal paths comprise radar returns from a target, and

wherein signal processing circuitry further comprises a trajectory calculator to interpolate between correlation output signals associated with different antennas to estimate an azimuth angle of the target.

14. The reciver of claim 13 wherein the plurality of antennas comprise a first set of antenna elements positioned with respect to a first elevation and a second set of antenna elements positioned with respect to a second elevation, and

wherein the trajectory calculator is to further estimate an elevation angle of the target based on differences between outputs of the correlations associated with the differing modulation waveforms used to modulate signals received from the antenna elements of the first and second sets.

15. The receiver of claim 13 wherein signal processing circuitry comprises:

one or more correlators to correlate combined modulated radar return signals with each of the modulation waveforms; and

fast-Fourier transform (FFT) circuitry to perform fast-Fourier transforms (FFTs) on correlation output signals from the one or more correlators for use in estimating a trajectory of the target.

16. The receiver of claim 15 wherein the trajectory calculator is to further estimate a velocity of the target based on frequency-domain samples provided by the FFT circuitry and a range of the target based on a sample rate of analog-to-digital conversion circuitry used to digitize the combined return signals.

17. The reciver of claim 13 wherein the target comprises at least one of an incoming projectile, a bullet, a rocket, a rocket-propelled grenade (RPG), a mortar shell, a missile and networked munitions.

18. The receiver of claim 11 wherein the signals received through the receive-signal paths comprise signals from a radio-frequency (RF) signal source;

wherein signal processing circuitry comprises;

one or more correlators to correlate the combined signal with each of the modulation waveforms; and

fast-Fourier transform (FFT) circuitry to perform fast-Fourier transforms (FFTs) on correlation output signals from the one or more correlators for use estimating a direction to the signal source.

19. A radar system comprising:

a plurality of modulators, each modulator to modulate radar return signals received through an associated receive-signal path with one of a plurality of differing modulation waveforms;

combining circuitry to combine the differently modulated return signals from each receive-signal path, each receive-signal path being associated with a different direction; and

signal processing circuitry to perform correlations on the combined and differently modulated radar return signals using the modulation waveforms to determine a location of a target.

20. The radar system of claim 19 wherein each receive-signal path receives signals from an associated one of a plurality of spatially-separated antennas, the antennas positioned to receive signals from at least slightly different directions, and

wherein the system further comprises a transmitter to simultaneously transmit a radar signal in each of the at least slightly different directions.

21. The radar system of claim 20 wherein the signal processing circuitry comprises one or more correlators to correlate combined modulated radar return signals with each of the modulation waveforms;

and

fast-Fourier transform (FFT) circuitry to perform fast-Fourier transforms (FFTs) on correlation output signals from the one or more correlators for use in estimating a trajectory of the target.

22. The radar system of claim 21 wherein the modulation waveforms comprise a plurality of waveforms generated from substantially orthogonal code sequences.

23. The radar system of claim 22 wherein signal processing circuitry further comprises a trajectory calculator to interpolate between correlation output signals associated with different antennas to estimate an azimuth angle and an elevation angle of the target.

24. The radar system of claim 21 wherein the modulation waveforms comprise either pseudo-orthogonal waveforms or quadratic-polyphase waveforms.

25. A method of operating a radar system comprising:

modulating radar return signals received through an associated receive-signal path with one of a plurality of differing modulation waveforms having a low cross-correlation product;

combining the differently modulated return signals from each receive-signal path, each receive-signal path being associated with a different direction; and

performing correlations on the combined and differently modulated radar return signals using the modulation waveforms to determine a location of a target.

26. The method of claim 25 wherein each receive-signal path receives signals from an associated one of a plurality of spatially-separated antennas, the antennas positioned to receive signals from at least slightly different directions, and

wherein the method further comprises simultaneously transmitting a radar signal in each of the at least slightly different directions.

27. The method of claim 26 performing correlations comprises correlating the combined modulated radar return signals with each of the modulation waveforms, and

wherein the method further comprises performing fast-Fourier transforms (FFTs) on correlation output signals from the one or more correlations for use in estimating a trajectory of the target.

28. The method of claim 27 wherein the modulation waveforms comprise a plurality of waveforms generated from substantially orthogonal code sequences.

29. The method of claim 28 further comprising interpolating between correlation output signals associated with different antennas to estimate an azimuth angle and an elevation angle of the target.

30. The method of claim 27 wherein the modulation waveforms comprise either pseudo-orthogonal waveforms or quadratic-polyphase waveforms.

31. A passive direction-finding system comprising:

a plurality of modulators, each modulator to modulate signals received from a signal source through an associated receive-signal path with one of a plurality of differing modulation waveforms having a low cross-correlation product;

combining circuitry to combine the modulated signals from each receive-signal path, each receive-signal path being associated with a different direction; and

signal processing circuitry to perform correlations on the combined modulated signals using the modulation waveforms to determine a direction to the signal source.

32. The passive direction-finding system of claim 31 wherein each receive-signal path receives signals from an associated one of a plurality of spatially-separated antennas, the antennas positioned to receive signals from at least slightly different directions.

33. The passive direction-finding system of claim 32 wherein the signal processing circuitry comprises one or more correlators to correlate combined modulated signals with each of the modulation waveforms;

and

fast-Fourier transform (FFT) circuitry to perform fast-Fourier transforms (FFTs) on correlation output signals from the one or more correlators for use in estimating the direction to and a frequency of the signal source.

34. The passive direction-finding system of claim 33 wherein the modulation waveforms comprise a plurality of waveforms generated from substantially orthogonal code sequences.

35. The passive direction-finding system of claim 34 wherein the modulation waveforms comprise either pseudo-orthogonal waveforms or quadratic-polyphase waveforms.

36. A method of locating a signal source comprising:

modulating signals received from a signal source through an associated receive-signal path with one of a plurality of differing modulation waveforms having a low cross-correlation product;

combining circuitry to combine the modulated signals from each receive-signal path, each receive-signal path being associated with a different direction; and

performing correlations on the combined modulated signals using the modulation waveforms to determine a direction to the signal source.

37. The method of claim 36 wherein each receive-signal path receives signals from an associated one of a plurality of spatially-separated antennas, the antennas positioned to receive signals from at least slightly different directions.

38. The method of claim 37 wherein performing correlations comprises correlating the combined modulated signals with each of the modulation waveforms, and

wherein the method further comprises performing fast-Fourier transforms (FFTs) on correlation output signals from the one or more correlators for use in estimating the direction to and a frequency of the signal source.

39. The method of claim 38 wherein the modulation waveforms comprise a plurality of waveforms generated from substantially orthogonal code sequences.

40. The method of the 38 wherein the modulation waveforms comprise either pseudo-orthogonal waveforms or quadratic-polyphase waveforms.