Method for improving monopulse processing of aperture segment outputs

• US 5,986,605 A
• Filed: 04/06/1998
• Issued: 11/16/1999
• Est. Priority Date: 05/23/1997
• Status: Expired due to Term

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Priebe, Leslie A., Holmes, Jerry D.
• Primary Examiner(s): Blum, Theodore M.
• Application Number:
  US09/056,070
• Time in Patent Office: 589 Days
• Field of Search: 342/427, 342/149
• US Class Current: 342/427
• CPC Class Codes: G01S 13/44 Monopulse radar, i.e. simultaneous lobing
• CPC Class Codes: G01S 13/4418 with means for eliminating radar-dependent errors in angle measurements, e.g. multipath effects
• CPC Class Codes: G01S 3/32 derived from different combinations of signals from separate antennas, e.g. comparing sum with difference

Abstract

A system and method for estimating azimuth angle, elevation angle and signal detection and which includes an antenna system having a plurality of elements, each element receiving a different concurrent portion of an incoming analog signal having a real and an imaginary portion. A converter is provided for each antenna element for converting each analog signal to digital form. A processor is provide for multiplying the sum of the real parts of the signals from a first group of the elements with the conjugate of the sum of the remainder of the elements to provided an estimated azimuth, elevation of signal detection measurement. In the case of a four element antenna, AzEst=Angle((A+B)*(C+D)Conjugate))=(x_A +iy_A +x_B +iy_B)*(x_C -iy_C +x_D -iy_D), ElEst=Angle((A+D)*(B+C)Conjugate))=(x_A +iy_A +x_D +iy_D)*(x_B -iy_B +x_C -iy_C) and Magnitude ((A+B*(C+D)Conjugate)) or Magnitude ((A+D*(B+C)Conjugate)). When the antenna system includes four antenna quadrants A, B, C and D, false detections due to responses coming from the sidelobe regions are suppressed by subtracting the offset OffsetAz=ScaleFactor*Magnitude(DeltaAz), where the offset is a scale factor to make the numbers come out correctly to provide a synthetic beam response: SyntheticAz=Magnitude((A+B)*(C+D)Conjugate)-OffsetAz the processor further including a comparator for comparing the Synthetic Az to a threshold to determine validity of the signal.

Claims

1. A system for estimating azimuth angle which comprises:

(a) an antenna system having a plurality of elements, each of said elements receiving a different concurrent portion of an incoming analog signal having a real and an imaginary portion;

(b) a converter for each said antenna element for converting each said analog signal to digital form; and

(c) a processor for multiplying the sum of the real and imaginary parts of said signals from a first group of said elements with the sum of the conjugates of the real and imaginary parts of said signals from the remainder of said elements to provide an estimated azimuth measurement;

where "group" includes one and where "angle" is defined as the angle relative to boresight.

2. The system of claim 1 wherein said antenna system includes four antenna elements A, B, C and D and where AzEst=Angle((A+B)*(C+D)Conjugate))=Angle)(x_A +iy_A +x_B +iy_B)*(x_C -iy_C +x_D -iy_D)).

3. A system for estimating elevation angle which comprises:

(a) an antenna system having a plurality of elements, each of said elements receiving a different concurrent portion of an incoming analog signal having a real and an imaginary portion;

(b) a converter for each said antenna element for converting each said analog signal to digital form; and

(c) a processor for multiplying the sum of the real and imaginary parts of said signals from a first group of said elements with the sum of the conjugate of the real and imaginary parts of said signals from the remainder of said elements to provide an estimated elevation measurement;

where "group" includes one and where "angle" is defined as the angle relative to boresight.

4. The system of claim 3 wherein said antenna system includes four antenna elements A, B, C and D and where ElEst=Angle((A+D)*(B+C)Conjugate))=Angle((x_A +iY_A +x_D +iY_D)*(x_B -iY_B +x_C -iY_C)).

5. A system for signal detection which comprises:

(a) an antenna system having a plurality of elements, each of said elements receiving a different concurrent portion of an incoming analog signal having a real and an imaginary portion;

(b) a converter for each said antenna element for converting each said analog signal to digital form; and

(c) a processor for multiplying the sum of the real and imaginary parts of said signals from a first group of said elements with the sum of the conjugates of the real and imaginary parts of said signals from the remainder of said elements to provide a signal detection measurement;

where "group" includes one.

6. The system of claim 5 wherein said antenna system includes four antenna elements A, B, C and D and where the magnitude of said signal is Magnitude ((A+B)*(C+D)Conjugate)).

7. The system of claim 5 wherein said antenna system includes four antenna elements A, B, C and D and where the magnitude of said signal is Magnitude ((A+D)*(B+C) Conjugate)).

8. The system of claim 5 wherein said antenna system includes four antenna elements A, B, C and D and wherein false detections due to responses coming from the sidelobe regions are suppressed by using the offset OffsetAz=ScaleFactor*Magnitude(DeltaAz), where the offset is a scale factor, to determine a synthetic beam response:

SyntheticAz=Magnitude((A+B)*(C+D)Conjugate)-OffsetAz, said processor further including a comparator for comparing said SyntheticAz to a threshold to determine validity of said SyntheticAz.

9. A method for estimating azimuth angle which comprises:

(a) providing an antenna system having a plurality of elements, each of said elements receiving a different concurrent portion of an incoming analog signal having a real and an imaginary portion;

(b) providing a converter for each said antenna element for converting each said analog signal to digital form; and

(c) multiplying the sum of the real and imaginary parts of said signals from a first group of said elements with the sum of the conjugates of the real and imaginary parts of said signals from the remainder of said elements to provide an estimated azimuth measurement;

where "group" includes one and where "angle" is defined as the angle relative to boresight.

10. The method of claim 9 wherein said antenna system is provided with four antenna elements A, B, C and D and where AzEst=Angle((A+B)*(C+D)Conjugate))=Angle((x_A +iy_A +x_B +iy_B)*(x_C -iy_C +x_D -iy_D)).

11. A method for estimating elevation angle which comprises:

(a) providing an antenna system having a plurality of elements, each of said elements receiving a different concurrent portion of an incoming analog signal having a real and an imaginary portion;

(b) providing a converter for each said antenna element for converting each said analog signal to digital form; and

(c) multiplying the sum of the real and imaginary parts of said signals from a first group of said elements with the sum of the conjugates of the real and imaginary parts of said signals from the remainder of said elements to provide an estimated elevation measurement;

where "group" includes one and where "angle" is defined as the angle relative to boresight.

12. The method of claim 11 wherein said antenna system is provided with four antenna elements A, B, C and D and where ElEst=Angle((A+D)*(B+C)Conjugate))=Angle((x_A +iy_A +x_D +iy_D)*(x_B -iY_B +x_C iy_C)).

13. A method for signal detection which comprises:

(a) providing an antenna system having a plurality of elements, each of said elements receiving a different concurrent portion of an incoming analog signal having a real and an imaginary portion;

(b) providing a converter for each said antenna element for converting each said analog signal to digital form; and

(c) multiplying the sum of the real and imaginary parts of said signals from a first group of said elements with the sum of the conjugates of the real and imaginary parts of said signals from the remainder of said elements to provide an estimated signal detection measurement;

where "group" includes one.

14. The method of claim 13 wherein said antenna system is provided with four antenna elements A, B, C and D and where the magnitude of said signal is Magnitude ((A+B)*(C+D)Conjugate).

15. The method of claim 13 wherein said antenna system is provided with four antenna elements A, B, C and D and where the magnitude of said signal is Magnitude ((A+D)*(B+C)Conjugate).

16. The method of claim 13 wherein said antenna system is provided with four antenna elements A, B, C and D and wherein false detections due to responses coming from the sidelobe regions are suppressed by using the offset OffsetAz=ScaleFactor*Magnitude(DeltaAz), where the offset is a scale factor, to determine a synthetic beam response:

SyntheticAz=Magnitude((A+B)*(C+D)Conjugate)-OffsetAz, said processor further including a comparator for comparing said SyntheticAz to a threshold to determine validity of said SyntheticAz.

17. A system comprising:

an antenna section having a plurality of segments which each produce a respective analog signal in response to an incoming signal, each of said analog signals including real and imaginary information;

an analog to digital converter section operative to convert each of said analog signals into a respective digital signal which includes real and imaginary information; and

a processor operative to identify first and second subsets of said digital signals which are different, and operative to multiply first digital information by second digital information in order to obtain third digital information, said first digital information being a function of each said digital signal in said first subset, and said second digital information being a function of the conjugate of each said digital signal in said second subset.

18. A system according to claim 17, wherein said processor is further operative to determine an angle as a function of said third digital information.

19. A system according to claim 17, wherein said processor is further operative to carry out sidelobe suppression as a function of said third digital information.

20. A system according to claim 17, wherein said segments include first and second segments, and said digital signals include first and second digital signals which correspond respectively to said first and second segments, said first subset including said first digital signal, said first digital information being said first digital signal, said second subset including said second digital signal, and said second digital information being a conjugate of said second digital signal.

21. A system according to claim 17, wherein said segments include first, second, third and fourth segments, and wherein said digital signals include first, second, third and fourth digital signals which respectively correspond to said first, second, third and fourth segments, said first subset including said first and second digital signals, said first digital information being a sum of said first and second digital signals, said second subset including said third and fourth digital signals, and said second digital information being a sum of the conjugates of said third and fourth digital signals.

22. A system according to claim 21, wherein said processor is further operative to determine an angle as a function of said third digital information.

23. A system according to claim 21, wherein said processor is further operative to multiple fourth digital information by fifth digital information in order to obtain sixth digital information, said fourth digital information being a sum of said first and fourth digital signals, and said fifth digital information being a sum of the conjugates of said second and third digital signals.

24. A system according to claim 23, wherein said processor is further operative to determine a first angle as a function of said third digital information, and to determine a second angle as a function of said sixth digital information.

25. A method, comprising the steps of:

producing from each of a plurality of segments of an antenna a respective analog signal in response to an incoming signal, each of said analog signals including real and imaginary information;

converting each of said analog signals into a respective digital signal which includes real and imaginary information;

identifying first and second subsets of said digital signals which are different; and

multiplying first digital information by second digital information in order to obtain third digital information, said first digital information being a function of each said digital signal in said first subset, and said second digital information being a function of the conjugate of each said digital signal in said second subset.

26. A method according to claim 25, further including the step of determining an angle as a function of said third digital information.

27. A method according to claim 25, further including the step of carrying out sidelobe suppression as a function of said third digital information.

28. A method according to claim 25, wherein said segments include first and second segments, wherein said digital signals include first and second digital signals which correspond respectively to said first and second segments, and wherein said identifying step is carried out by including said first digital signal in said first subset and said second digital signal in said second subset, said first digital information being said first digital signal, and said second digital information being the conjugate of said second digital signal.

29. A method according to claim 25, wherein said segments include first, second, third and fourth segments, wherein said digital signals include first, second, third and fourth digital signals which respectively correspond to said first, second, third and fourth segments, and wherein said identifying step is carried out by including said first and second digital signals in said first subset and by including said third and fourth digital signals in said second subset, said first digital information being a sum of said first and second digital signals, and said second digital information being a sum of the conjugates of said third and fourth digital signals.

30. A method according to claim 29, including the step of determining an angle as a function of said third digital information.

31. A method according to claim 29, including the further step of multiplying fourth digital information by fifth digital information in order to obtain sixth digital information, said fourth digital information being a sum of said first and fourth digital signals, and said fifth digital information being a sum of the conjugates of said second and third digital signals.

32. A method according to claim 31, including the steps of determining a first angle as a function of said third digital information, and determining a second angle as a function of said sixth digital information.