IMPROVEMENTS IN AND RELATING TO RADAR

• US 20160161604A1
• Filed: 07/02/2014
• Published: 06/09/2016
• Est. Priority Date: 07/10/2013
• Status: Active Grant

• Current Assignee: BAE Systems Plc
• Original Assignee: BAE Systems Plc
• Inventors: CLARK, MARCUS EDWARD
• Granted Patent: US 10,459,075 B2
• Time in Patent Office: Days
• CPC Class Codes: G01S 13/424 Stacked beam radar
• CPC Class Codes: G01S 13/4418 with means for eliminating radar-dependent errors in angle measurements, e.g. multipath effects
• CPC Class Codes: G01S 7/2813 Means providing a modification of the radiation pattern for cancelling noise, clutter or interfering signals, e.g. side lobe suppression, side lobe blanking, null-steering arrays specially adapted to secondary radar systems G01S13/762; aerials or aerials systems H01Q21/29, H01Q25/00
• CPC Class Codes: H01Q 3/2617 Array of identical elements

Abstract

A radar apparatus (5) for detecting multipath signal propagation when determining an elevation angle of an object, comprising an antenna array with which the radar apparatus is arranged to form at least three separate antenna beams (11, 12, 13) comprising a first antenna beam (11) having an angle of elevation above horizontal, and a separate second antenna beam (12) having an angle of elevation at or above horizontal which is less than that of the first antenna beam, and a separate third antenna beam (13) having an angle of elevation below horizontal. The apparatus is arranged to transmit radio pulses from the antenna array; to receive return radio signals within the first, second and third antenna beams; to calculate a measure of the magnitude of a return radio signal received within the third antenna beam using all of said received radio signals collectively; and, to detect multipath signal propagation using said measure.

Claims

1. A radar apparatus for detecting multipath signal propagation when determining an elevation angle of an object, comprising an antenna array with which the radar apparatus is arranged:

to form at least three separate antenna beams comprising a first antenna beam having an angle of elevation above horizontal, and a separate second antenna beam having an angle of elevation at or above horizontal which is less than that of the first antenna beam, and a separate third antenna beam having an angle of elevation below horizontal;

to transmit radio pulses from the antenna array;

to receive return radio signals within the first, second and third antenna beams;

to calculate a measure of the magnitude of a return radio signal received within the third antenna beam using all of said received radio signals collectively; and

,

to detect multipath signal propagation using said measure.

2. A radar apparatus according to claim 1 wherein said measure is the magnitude of an eigenvalue of the cross-correlation matrix of return radio signals received within the at least three separate antenna beams.

3. A radar apparatus according to claim 2 further arranged to determine an elevation of a said object using eigenvectors of the cross-correlation matrix other than an eigenvector thereof associated with said eigenvalue if said magnitude of the eigenvalue exceeds a threshold value.

4. A radar apparatus according to claim 2, further arranged to beam-form one or more of said antenna beams to locate a null in the beam pattern of the antenna array at the angular location associated with said detected multi-path signal propagation if said magnitude of the eigenvalue exceeds a threshold value.

5. A radar apparatus according to claim 1, arranged such that the angular separation in elevation between the first and second antenna beams is substantially the same as the angular separation in elevation between the second and third antenna beams.

6. A radar apparatus according to claim 1, in which one, some or each of the first, second and third radar beams is a pencil beam.

7. A radar apparatus according to claim 1, in which the antenna array comprises a first antenna unit arranged to form independently said first antenna beam, a second antenna unit arranged to form independently said second antenna beam, and a third antenna unit arranged to form independently said third antenna beam.

8. A radar apparatus according to claim 1 in which the antenna array comprises a phased array of antennas which the radar apparatus is arranged to control collectively to form said first antenna beam, said second antenna beam, and said third antenna beam.

9. A mono-pulse radar apparatus comprising the radar apparatus of claim 1.

10. A method for detecting multipath signal propagation when determining an elevation angle of an object using radar, the method comprising:

forming, with an antenna array, at least three separate antenna beams comprising a first antenna beam having an angle of elevation above horizontal, and a separate second antenna beam having an angle of elevation at or above horizontal which is less than that of the first antenna beam, and a separate third antenna beam having an angle of elevation below horizontal;

transmitting radio pulses from the antenna array;

receiving return radio signals within the first, second and third antenna beams;

calculating a measure of the magnitude of a return radio signal received within the third antenna beam using all of said received radio signals collectively; and

,

detecting multipath signal propagation using said measure.

11. A method according to claim 10 wherein said measure is the magnitude of an eigenvalue of the cross-correlation matrix of return radio signals received within the at least three separate antenna beams.

12. A method according to claim 11 including determining an elevation of a said object using eigenvectors of the cross-correlation matrix other than an eigenvector thereof associated with said eigenvalue if said magnitude of the eigenvalue exceeds a threshold value.

13. A method according to claim 11 including beam-forming one or more of said antenna beams to locate a null in the beam pattern of the antenna array at the angular location associated with said detected multi-path signal propagation if said magnitude of the eigenvalue exceeds a threshold value.

14. A method according to claim 10 including forming said antenna beams such that the angular separation in elevation between the first and second antenna beams is substantially the same as the angular separation in elevation between the second and third antenna beams.

15. A method according to claim 10 including forming one, some or each of the first, second and third radar beams as a pencil beam.

16. (canceled)

17. (canceled)

18. A radar apparatus, configured to:

form, with an antenna array, at least three separate antenna beams comprising a first antenna beam having an angle of elevation above horizontal, and a separate second antenna beam having an angle of elevation at or above horizontal which is less than that of the first antenna beam, and a separate third antenna beam having an angle of elevation below horizontal;

transmit radio pulses from the antenna array;

receive return radio signals within the first, second and third antenna beams;

calculate a measure of the magnitude of a return radio signal received within the third antenna beam using all of said received radio signals collectively; and

,

detect multipath signal propagation using said measure.

19. A radar apparatus according to claim 18 wherein said measure is the magnitude of an eigenvalue of the cross-correlation matrix of return radio signals received within the at least three separate antenna beams, wherein the apparatus is further configured to:

determine an elevation of a said object using eigenvectors of the cross-correlation matrix other than an eigenvector thereof associated with said eigenvalue if said magnitude of the eigenvalue exceeds a threshold value; and

beam-form one or more of said antenna beams to locate a null in the beam pattern of the antenna array at the angular location associated with said detected multi-path signal propagation if said magnitude of the eigenvalue exceeds a threshold value.

20. A radar apparatus according to claim 18, wherein the angular separation in elevation between the first and second antenna beams is substantially the same as the angular separation in elevation between the second and third antenna beams.

21. A radar apparatus according to claim 18, in which one, some or each of the first, second and third radar beams is a pencil beam.

22. A mono-pulse radar apparatus comprising the radar apparatus of claim 18.