Creating and processing universal radar waveforms

• US 8,378,878 B2
• Filed: 08/05/2010
• Issued: 02/19/2013
• Est. Priority Date: 08/05/2010
• Status: Active Grant

• Current Assignee: Arete Associates
• Original Assignee: Arete Associates
• Inventors: Burri, Jeremy Francis, Farris, Michael Howard, Pohlman, Matthew Michael, Potter, Randall Edward
• Primary Examiner(s): Keith, Jack W
• Assistant Examiner(s): BYTHROW, PETER M
• Application Number:
  US12/851,469
• Publication Number:
  US 20120032839A1
• Time in Patent Office: 929 Days
• Field of Search: 342134-137, 342/160, 342/196
• US Class Current: 342/25.R
• CPC Class Codes: G01S 13/222 using random or pseudorandom pulse repetition frequency
• CPC Class Codes: G01S 13/26 wherein the transmitted pulses use a frequency- or phase-modulated carrier wave
• CPC Class Codes: G01S 13/904 SAR modes
• CPC Class Codes: G01S 7/282 Transmitters

Abstract

A new approach to radar imaging is described herein, in which radar pulses are transmitted wi th an uneven sampling scheme and subsequently processed with novel algorithms to produce images of equivalent resolution and quality as standard images produced using standard synthetic aperture radar (SAR) waveforms and processing techniques. The radar data collected with these waveforms can be used to create many other useful products such as moving target indication (MTI) and high resolution terrain information (HRTI). The waveform and the correction algorithms described herein allow the algorithms of these other radar products to take advantage of the quality Doppler resolution.

Claims

1. A radar transmission system comprising:

a transmitter system configured to generate one or more radar signals; and

an antenna system having spatially-separated elements and configured to radiate the one or more radar signals from the spatially-separated elements,

wherein the transmitter system and/or the antenna system are configured such that the radiated radar signals include a pattern of spatially-separated radar pulses, each from a different one of the spatially-separated antenna elements, the pattern of pulses having;

at least two neighboring radar pulses that have a spatial separation that is substantially unequal to the spatial separation between at least two other neighboring radar pulses in the pattern of pulses;

a mainlobe radiation pattern with a width that is near or substantially equal to the minimum possible mainlobe width; and

sidelobe radiation patterns with substantially even energy distribution.

2. The radar transmission system of claim 1 further comprising a processing system configured to generate pulses using a Fourier transform which are used by the transmitter system to generate the one or more radar signals.

3. The radar transmission system of claim 1 wherein the radiated pattern of pulses has a quadratic residue (QR) pattern.

4. The radar transmission system of claim 1 wherein the radiated pattern of pulses has a pseudo-random pattern.

5. The radar transmission system of claim 1 wherein:

the elements of the antenna system are spatially-separated in two dimensions;

the pattern of radar pulses includes pulses spatially-separated in the two dimensions, and

the substantially unequal separation includes substantially unequal separation in the spatial locations from which the radar pulses are radiated by the antenna system in both of the two dimensions.

6. The radar transmission system of claim 1 wherein the transmitter system is configured such that the radiated radar signals include a pattern of time-separated radar pulses having at least two sequential radar pulses with a time separation that is substantially unequal to the time separation between at least two other sequential radar pulses in the pattern of pulses.

7. The radar transmission system of claim 1 wherein the antenna elements are unequally spaced.

8. The radar transmission system of claim 1 wherein the antenna elements are equally spaced, but the transmission system is configured to selectively drive the elements so as to cause the driven elements to have the substantially unequal spatial separations.

9. Non-transitory, tangible, computer-readable storage media containing programming code which, when executed by a computer system, causes an antenna system to radiate radar signals which include a pattern of pulses having:

at least two neighboring radar pulses that have a spatial separation that is substantially unequal to the spatial separation between at least two other neighboring radar pulses in the pattern of pulses; and

a mainlobe radiation pattern with a width that is near or substantially equal to the minimum possible mainlobe width; and

sidelobe radiation patterns with substantially even energy distribution.

10. The computer-readable storage media of claim 9 wherein the programming code, when executed by a computer system, causes the computer system to generate pulses using a Fourier transform which are converted into the radar signals by a transmitter system.

11. The computer-readable storage media of claim 9 wherein the pattern of radar pulses has a quadratic residue (QR) pattern.

12. The computer-readable storage media of claim 9 wherein the pattern of radar pulses has a pseudo-random pattern.

13. The computer-readable storage media of claim 9 wherein

the pattern of radar pulses includes pulses spatially-separated in two dimensions;

and

the substantially unequal separation includes substantially unequal separation in both of the two dimensions.

14. The computer-readable storage media of claim 9 wherein the programming code, when executed by the computer system, causes the radiated radar signals to include a pattern of time-separated radar pulses having at least two sequential radar pulses with a time separation that is substantially unequal to the time separation between at least two other sequential radar pulses in the pattern of pulses.

15. A radar reception system comprising:

a receiver configured to receive a radar signal which includes a first data set having a plurality of values based on a radar waveform return from a set of transmitted radar pulses; and

a processing system configured to create a second data set comprising the first data set minus at least one significant value from the first data set and its effects on other values within the first data set when the set of transmitted radar pulses was transmitted with;

a spatial separation between at least two neighboring pulses that is substantially unequal to the spatial separation between at least two other neighboring pulses in the set;

a mainlobe radiation pattern with a width that is near or substantially equal to the minimum possible width; and

sidelobe radiation patterns with a substantially even distribution of energy.

16. The radar reception system of claim 15 wherein the processing system is configured to:

create a third data set comprising the at least one significant value from the first data set; and

combine the second and third datasets.

17. The radar reception system of claim 15 wherein the first data set includes a plurality of transformed values.

18. The radar reception system of claim 17 wherein the plurality of transformed values are frequency values.

19. The radar reception system of claim 15 wherein the at least one significant value includes a peak value in a frequency domain.

20. The radar reception system of claim 15 wherein the second data set includes a number of peak values from the first data set chosen based on predetermined selection criteria.

21. The radar reception system of claim 15 wherein the processing system is configured to determine the effects of the at least one significant value by calculating a plurality of propagated effects from the at least one significant value.

22. The radar reception system of claim 15 wherein the processing system is configured to create the second data set by:

identifying at least one peak value in the first data set;

creating a peak correction function approximation using the at least one peak value; and

removing the peak correction function approximation from the first data.

23. The radar reception system of claim 15 wherein:

the pattern of radar pulses includes pulses spatially-separated in two dimensions; and

the substantially unequal separation includes substantially unequal separation in both of the two dimensions.

24. The radar reception system of claim 15 wherein the radiated radar signals include a pattern of time-separated radar pulses having at least two sequential radar pulses with a time separation that is substantially unequal to the time separation between at least two other sequential radar pulses in the pattern of pulses.

25. Non-transitory, tangible, computer-readable storage media containing programming code which, when executed by a computer system, creates a second data set comprising a first data set having a plurality of values based on a radar waveform return from a set of transmitted radar pulses minus at least one significant value from the first data set and its effects on other values within the first data set when the set of transmitted radar pulses has:

a spatial separation between at least two neighboring pulses that is substantially unequal to the spatial separation between at least two other neighboring pulses in the set;

a mainlobe radiation pattern with a width that is near or substantially equal to the minimum possible width; and

sidelobe radiation patterns with a substantially even distribution of energy.

26. The computer-readable storage media of claim 25 wherein the programming code, when executed by the computer system:

creates a third data set comprising the at least one significant value from the first data set; and

combines the second and third datasets.

27. The computer-readable storage media of claim 25 wherein the first data set includes a plurality of transformed values.

28. The computer-readable storage media of claim 27 wherein the plurality of transformed values are frequency values.

29. The computer-readable storage media of claim 25 wherein the at least one significant value includes a peak value in a frequency domain.

30. The computer-readable storage media of claim 25 wherein the second data set includes a number of peak values from the first data set chosen based on predetermined selection criteria.

31. The computer-readable storage media of claim 25 wherein the programming code, when executed by the computer system, determines the effects of the at least one significant value by calculating a plurality of propagated effects from the at least one significant value.

32. The computer-readable storage media of claim 25 wherein the programming code, when executed by the computer system, creates the second data set by:

identifying at least one peak value in the first data set;

creating a peak correction function approximation using the at least one peak value; and

removing the peak correction function approximation from the first data.

33. The computer-readable storage media of claim 25 wherein:

the set of radar pulses are spatially-separated in two dimensions; and

the substantially unequal separation includes substantially unequal separation in both of the two dimensions.

34. The computer-readable storage media of claim 25 wherein the set of radar pulses include a pattern of time-separated radar pulses having at least two sequential radar pulses with a time separation that is substantially unequal to the time separation between at least two other sequential radar pulses in the pattern of pulses.

35. A radar transmission system comprising:

a transmitter system configured to generate one or more radar signals; and

an antenna system having spatially-separated elements and configured to radiate the one or more radar signals from the spatially-separated elements,

wherein the transmitter system and/or the antenna system are configured such that the radiated radar signals include a pattern of spatially-separated radar pulses, each from a different one of the spatially-separated antenna elements, the pattern of radar pulses having at least two neighboring radar pulses that have a spatial separation that is at least twice the shortest spatial separation between at least two other neighboring radar pulses in the pattern of pulses.

36. The radar transmission system of claim 35 further comprising a processing system configured to generate pulses using a Fourier transform which are used by the transmitter system to generate the one or more radar signals.

37. The radar transmission system of claim 35 wherein the radiated pattern of pulses has a quadratic residue (QR) pattern.

38. The radar transmission system of claim 35 wherein the radiated pattern of pulses has a pseudo-random pattern.

39. The radar transmission system of claim 35 wherein:

the elements of the antenna system are spatially-separated in two dimensions;

the pattern of radar pulses includes pulses spatially-separated in the two dimensions, and

the substantially unequal separation includes substantially unequal separation in the spatial locations from which the radar pulses are radiated by the antenna system in both of the two dimensions.

40. The radar transmission system of claim 35 wherein the transmitter system is configured such that the radiated radar signals include a pattern of time-separated radar pulses having at least two sequential radar pulses with a time separation that is substantially unequal to the time separation between at least two other sequential radar pulses in the pattern of pulses.

41. The radar transmission system of claim 35 wherein the antenna elements are unequally spaced.

42. The radar transmission system of claim 35 wherein the antenna elements are equally spaced, but the transmission system is configured to selectively drive the elements so as to cause the driven elements to have the substantially unequal spatial separations.

43. Non-transitory, tangible, computer-readable storage media containing programming code which, when executed by a computer system, causes an antenna system to radiate radar signals which include a pattern of pulses having at least two neighboring radar pulses that have a spatial separation that is at least twice the shortest spatial separation between at least two other neighboring radar pulses in the pattern of pulses.

44. The computer-readable storage media of claim 43 wherein the programming code, when executed by a computer system, causes the computer system to generate pulses using a Fourier transform which are converted into the radar signals by a transmitter system.

45. The computer-readable storage media of claim 43 wherein the pattern of radar pulses has a quadratic residue (QR) pattern.

46. The computer-readable storage media of claim 43 wherein the pattern of radar pulses has a pseudo-random pattern.

47. The computer-readable storage media of claim 43 wherein

the pattern of radar pulses includes pulses spatially-separated in two dimensions;

and

the substantially unequal separation includes substantially unequal separation in both of the two dimensions.

48. The computer-readable storage media of claim 43 wherein the programming code, when executed by the computer system, causes the radiated radar signals to include a pattern of time-separated radar pulses having at least two sequential radar pulses with a time separation that is substantially unequal to the time separation between at least two other sequential radar pulses in the pattern of pulses.

49. A radar reception system comprising:

a receiver configured to receive a radar signal which includes a first data set having a plurality of values based on a radar waveform return from a set of transmitted radar pulses; and

a processing system configured to create a second data set comprising the first data set minus at least one significant value from the first data set and its effects on other values within the first data set when the set of transmitted radar pulses was transmitted with a pattern of radar pulses having at least two neighboring radar pulses that have a spatial separation that is at least twice the shortest spatial separation between at least two other neighboring radar pulses in the pattern of pulses.

50. The radar reception system of claim 49 wherein the processing system is configured to:

create a third data set comprising the at least one significant value from the first data set; and

combine the second and third datasets.

51. The radar reception system of claim 49 wherein the first data set includes a plurality of transformed values.

52. The radar reception system of claim 51 wherein the plurality of transformed values are frequency values.

53. The radar reception system of claim 49 wherein the at least one significant value includes a peak value in a frequency domain.

54. The radar reception system of claim 49 wherein the second data set includes a number of peak values from the first data set chosen based on predetermined selection criteria.

55. The radar reception system of claim 49 wherein the processing system is configured to determine the effects of the at least one significant value by calculating a plurality of propagated effects from the at least one significant value.

56. The radar reception system of claim 49 wherein the processing system is configured to create the second data set by:

identifying at least one peak value in the first data set;

creating a peak correction function approximation using the at least one peak value; and

removing the peak correction function approximation from the first data.

57. The radar reception system of claim 49 wherein:

the pattern of radar pulses includes pulses spatially-separated in two dimensions; and

the substantially unequal separation includes substantially unequal separation in both of the two dimensions.

58. The radar reception system of claim 49 wherein the radiated radar signals include a pattern of time-separated radar pulses having at least two sequential radar pulses with a time separation that is substantially unequal to the time separation between at least two other sequential radar pulses in the pattern of pulses.

59. Non-transitory, tangible, computer-readable storage media containing programming code which, when executed by a computer system, creates a second data set comprising a first data set having a plurality of values based on a radar waveform return from a set of transmitted radar pulses minus at least one significant value from the first data set and its effects on other values within the first data set when the set of transmitted radar pulses has at least two neighboring radar pulses that have a spatial separation that is at least twice the shortest spatial separation between at least two other neighboring radar pulses in the pattern of pulses.

60. The computer-readable storage media of claim 59 wherein the programming code, when executed by the computer system:

creates a third data set comprising the at least one significant value from the first data set; and

combines the second and third datasets.

61. The computer-readable storage media of claim 59 wherein the first data set includes a plurality of transformed values.

62. The computer-readable storage media of claim 61 wherein the plurality of transformed values are frequency values.

63. The computer-readable storage media of claim 59 wherein the at least one significant value includes a peak value in a frequency domain.

64. The computer-readable storage media of claim 59 wherein the second data set includes a number of peak values from the first data set chosen based on predetermined selection criteria.

65. The computer-readable storage media of claim 59 wherein the programming code, when executed by the computer system, determines the effects of the at least one significant value by calculating a plurality of propagated effects from the at least one significant value.

66. The computer-readable storage media of claim 59 wherein the programming code, when executed by the computer system, creates the second data set by:

identifying at least one peak value in the first data set;

creating a peak correction function approximation using the at least one peak value; and

removing the peak correction function approximation from the first data.

67. The computer-readable storage media of claim 59 wherein:

the set of radar pulses are spatially-separated in two dimensions; and

the substantially unequal separation includes substantially unequal separation in both of the two dimensions.

68. The computer-readable storage media of claim 59 wherein the set of radar pulses include a pattern of time-separated radar pulses having at least two sequential radar pulses with a time separation that is substantially unequal to the time separation between at least two other sequential radar pulses in the pattern of pulses.