RADAR CLUTTER SUPPRESSION SYSTEM

• US 20120293361A1
• Filed: 05/17/2012
• Published: 11/22/2012
• Est. Priority Date: 05/17/2011
• Status: Active Grant

• Current Assignee: Navico Incorporated (Brunswick Corporation)
• Original Assignee: Navico Holding A.S. (Brunswick Corporation)
• Inventors: Mowbray, Robert Stephen, Phillips, Roger
• Granted Patent: US 9,213,088 B2
• Time in Patent Office: Days
• US Class Current: 342/159
• CPC Class Codes: G01S 13/02 Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
• CPC Class Codes: G01S 13/5242 with means for platform motion or scan motion compensation, e.g. airborne MTI
• CPC Class Codes: G01S 13/5244 Adaptive clutter cancellation specially adapted for airborne MTI, G01S13/5242
• CPC Class Codes: G01S 7/2922 by using a controlled threshold
• CPC Class Codes: G01S 7/2925 by using shape of radiation pattern
• CPC Class Codes: G01S 7/2927 by deriving and controlling a threshold value
• CPC Class Codes: G01S 7/34 Gain of receiver varied automatically during pulse-recurrence period, e.g. anti-clutter gain control
• CPC Class Codes: G01S 7/414 Discriminating targets with respect to background clutter

Abstract

Sidelobe suppression methods and systems for use in processing radar video streams generated by rotational radar antenna scanners. The sidelobe suppression methods function in parallel with traditional Sensitivity Control (SC) processing by selectively reducing sensitivity where necessary depending on sidelobe suppression schemes that can be either directional, omni-directional (non-directional), or a combination of these.

Claims

1. A method of suppressing sidelobe clutter for a radar signal processing system that receives a radar video stream from a radar antenna scanner and applies Sensitivity Control (SC) processing to the radar video stream based on an SC threshold profile that defines an echo return intensity threshold over range, comprising:

determining estimates of the sidelobe clutter contribution levels (herein;

sidelobe estimates) based on a buffer of the radar video stream and an antenna beam pattern response model of the radar antenna; and

selectively modifying the SC threshold profile based on the determined estimates of the sidelobe clutter contribution levels.

2. A method according to claim 1 wherein the radar video stream comprises a stream of azimuthal vector data, each azimuthal vector representing the echo return intensities at a number of range samples for an azimuthal direction in the radar antenna scanner sweep.

3. A method according to claim 2 wherein determining sidelobe estimates comprises determining sidelobe estimates for each new azimuthal vector in the radar video stream such that each azimuthal vector has corresponding sidelobe estimates.

4. A method according to claim 3 wherein determining sidelobe estimates for each azimuthal vector comprises, for each azimuthal vector, determining the sidelobe estimates based on a buffer of the radar video stream centered about the azimuthal vector.

5. A method according to claim 4 wherein determining the sidelobe estimates for each azimuthal vector comprises, for each azimuthal vector, generating a sidelobe contribution vector representing the sidelobe estimates for the azimuthal vector, the sidelobe contribution vector comprising estimates of the maximum sidelobe contribution levels at each range sample calculated based on the buffer of the radar video stream and the antenna beam pattern response model.

6. A method according to claim 5 wherein determining the sidelobe estimates for each azimuthal vector comprises, for each azimuthal vector, generating a set of individual candidate sidelobe levels for each range by applying the antenna beam pattern response model to the cross-range samples within the azimuthal buffer range, and generating the sidelobe contribution vector by selecting at each range sample the maximum of the calculated set of individual candidate sidelobe levels for the range.

7. A method according to claim 1 wherein selectively modifying the SC threshold profile comprises increasing the threshold levels of the SC threshold profile in range regions where the determined sidelobe estimates exceed the original threshold levels.

8. A method according to claim 7 wherein increasing the threshold levels of the SC threshold profile comprises increasing the threshold level of the SC threshold profile to a level substantially equal to or above the corresponding sidelobe estimate at ranges where the original threshold levels are exceeded by the corresponding sidelobe estimate.

9. A method according to claim 2 wherein selectively modifying the SC threshold profile comprises selectively modifying the SC threshold profile for each new azimuthal vector in the radar video stream prior to SC processing of that new azimuthal vector, and then subsequently restoring the original SC threshold profile after each azimuthal vector has been SC processed.

10. A sidelobe clutter suppression system for a radar signal processing system that receives a radar video stream from a radar antenna scanner and applies Sensitivity Control (SC) processing to the radar video stream based on an SC threshold profile that defines an echo intensity threshold over range, comprising:

a module configured to generate estimates of the sidelobe clutter contribution levels (herein;

sidelobe estimates) based on a buffer of the radar video stream and an antenna beam pattern response model of the radar antenna; and

a module configured to selectively modify the SC threshold profile based on the estimates of the sidelobe clutter contribution levels.

11. A method of suppressing sidelobe clutter for a radar signal processing system that receives a radar video stream from a radar antenna scanner and applies Sensitivity Control (SC) processing to the radar video stream based on an SC threshold profile that defines an echo return intensity threshold over range, comprising:

determining the peak echo return intensity level (herein;

peak return level) at each range based on radar video stream representing a full scanner sweep; and

selectively modifying the SC threshold profile based on the determined peak echo return intensity levels from the full scanner sweep.

12. A method according to claim 11 wherein the radar video stream comprises a stream of azimuthal vector data, each azimuthal vector representing the echo return intensities at a number of range samples for an azimuthal direction in the radar antenna scanner sweep.

13. A method according to claim 12 wherein determining the peak return level at each range comprises determining the peak return level for each range based on the maximum echo return intensity from all or a sample of azimuthal vectors in a full sweep of the radar antenna scanner.

14. A method according to claim 12 wherein determining the peak return level at each range comprises, for each azimuthal vector, generating a peak return level vector comprising the peak return levels at each range sample based on a buffer of the radar video stream comprising azimuthal vectors within an azimuthal buffer range of 360°

centered about or preceding the azimuthal vector, and selectively modifying the SC threshold profile comprises, for each azimuthal vector, selectively modifying the SC threshold profile based on the generated peak return level vector for the azimuthal vector prior to SC processing of the azimuthal vector.

15. A method according to claim 12 wherein determining the peak return level at each range comprises generating a peak return level vector once for each full sweep, the peak return level vector comprising the peak return levels at each range based on a buffer of the radar video stream comprising azimuthal vectors within an azimuthal buffer range of 360°

preceding the sweep, and selectively modifying the SC threshold profile comprises selectively modifying the SC profile once for each full sweep based on the generated peak return level vector for that sweep prior to SC processing of the radar video stream of the sweep.

16. A method according to claim 11 further comprising modifying the determined peak return levels based on a selected antenna sidelobe margin factor to generate modified peak return levels and selectively modifying the SC threshold profile comprises selectively modifying the SC threshold profile based on the modified peak return levels, and wherein the sidelobe margin factor is selected based on the antenna characteristics of the radar antenna scanner.

17. A method according to claim 11 wherein selectively modifying the SC threshold profile based on the determined peak return levels comprises increasing the threshold levels of the SC threshold profile in range regions where the peak return levels exceeds the original threshold levels.

18. A method according to claim 17 wherein increasing the threshold levels of the threshold profile comprises increasing the threshold level of the SC threshold profile to a level subsequently equal to or above the corresponding peak return level at ranges where the original threshold levels are exceeded by their corresponding peak return level.

19. A method according to claim 12 wherein selectively modifying the SC threshold profile comprises selectively modifying the SC threshold profile for each new azimuthal vector in the radar video stream prior to SC processing of that new azimuthal vector, and then subsequently restoring the original SC threshold profile after each azimuthal vector has been SC processed.

20. A radar signal processing system that receives a radar video stream from a radar antenna scanner and applies Sensitivity Control (SC) processing to the radar video stream based on an SC threshold profile that defines an echo intensity threshold over range and which is configured to carry out the method according to claim 11, comprising:

a module configured to determine the peak echo return intensity level (herein;

peak return level) at each range based on radar video stream representing a full scanner sweep; and

a module configured to selectively modify the SC threshold profile based on the determined peak echo return intensity levels from the full scanner sweep.