Artifact reduction within a SAR image

• US 10,018,718 B1
• Filed: 10/29/2015
• Issued: 07/10/2018
• Est. Priority Date: 10/29/2015
• Status: Active Grant

• Current Assignee: National Technology & Engineering Solutions Of Sandia LLC (Honeywell International Inc.)
• Original Assignee: National Technology & Engineering Solutions Of Sandia LLC (Honeywell International Inc.)
• Inventors: Musgrove, Cameron, Naething, Richard M., Ormesher, Richard C.
• Primary Examiner(s): Bythrow, Peter M
• Application Number:
  US14/927,130
• Time in Patent Office: 985 Days
• CPC Class Codes: G01S 13/904 SAR modes
• CPC Class Codes: G01S 7/023 Interference mitigation, e.g. reducing or avoiding non-intentional interference with other HF-transmitters, base station transmitters for mobile communication or other radar systems, e.g. using electro-magnetic interference [EMI] reduction techniques auxiliary means for detecting or identifying radar signals or the like G01S7/021; means for anti-jamming G01S7/36
• CPC Class Codes: G01S 7/292 Extracting wanted echo-signals
• CPC Class Codes: G01S 7/414 Discriminating targets with respect to background clutter

Abstract

The various technologies presented herein relate to reducing and/or filtering undesired artifacts in a SAR image, wherein the artifacts are generated by RF interference resulting from a communication signal being included in a radar return which also comprises radar clutter. The radar return is separated into two subapertures, a first subaperture comprising radar clutter only, and a second subaperture comprising radar clutter and the communication signal. The communication signal is extracted from the second subaperture and reapplied to the initially received radar return. Reapplication of the communication signal to the radar return enables any undesired artifacts arising from the communication signal to have their return strength reduced or minimized, while maintaining any desired radar returns in the SAR image.

Claims

1. A method, comprising:

extracting a communication signal from a received radar signal, wherein the radar signal comprises radar clutter and the communication signal is bandwidth limited according to at least one parameter associated with the radar clutter, wherein extracting the communication signal from the received radar signal comprises;

converting a first portion of the radar clutter to a first rectangular array forming a first subaperture; and

converting the communication signal and a second portion of the radar clutter to a second rectangular array forming a second subaperture, wherein the first subaperture and the second subaperture have the same area, and further wherein the communication signal is extracted from the received radar signal based upon the first subaperture and the second subaperture;

responsive to extracting the communication signal from the received radar signal, determining a spectral estimation of the communication signal; and

filtering the received radar signal with the communication signal spectral estimation, wherein the filtering removes from the received radar signal an artifact generated due to interference between the communication signal and the radar clutter.

2. The method of claim 1, wherein prior to extracting the communication signal from the received radar signal, the received radar signal is deramped and sampled.

3. The method of claim 1, wherein extracting the communication signal from the received radar signal further comprises:

determining a radar signature of the first subaperture, wherein the communication signal is extracted from the received radar signal based upon the radar signature of the first subaperture.

4. The method of claim 3, wherein extracting the communication signal from the received radar signal further comprises:

filtering the second subaperture with the radar signature of the first subaperture leaving a signal residue, wherein the signal residue is the communication signal.

5. The method of claim 1, wherein the communication signal is at least one of a preamble, a data symbol, or communication data.

6. The method of claim 1, wherein the communication signal has a shorter duration than the duration of the radar clutter.

7. The method of claim 1, wherein a bandwidth of the communication signal is less than a bandwidth of the radar clutter.

8. The method of claim 1, further comprising generating a radar image based upon the filtered received signal, wherein the radar image is a synthetic aperture radar image.

9. A system comprising:

at least one processor; and

memory that comprises instructions that, when executed by the at least one processor, cause the at least one processor to perform acts comprising;

receiving a signal comprising a combination of a communication signal and radar clutter, wherein the communication signal has a frequency configured in accordance with a frequency of a radar transmission signal originating the radar clutter;

extracting the communication signal from the received signal, wherein extracting the communication signal from the received signal comprises;

converting the received signal from a polar format to a rectangular grid having an X dimension and a Y dimension; and

separating the rectangular grid into two equally sized regions, a first region being a first subaperture comprising a first portion of the radar clutter and a second region being a second subaperture comprising a second portion of the radar clutter and the communication signal, wherein the communication signal is extracted from the received signal based upon the first subaperture and the second subaperture;

responsive to extracting the communication from the received signal, determining a spectral estimation of the communication signal; and

filtering the received signal with the communication signal spectral estimation, wherein the filtering removes from the received signal an artifact generated due to interference between the communication signal and the radar clutter.

10. The system of claim 9, wherein extracting the communication signal from the received signal further comprises:

determining a radar signature of the first portion of the radar clutter, wherein the communication signal is extracted from the received signal based upon the radar signature.

11. The system of claim 9, wherein a bandwidth of the communication signal is configured in accordance with at least one parameter associated with the radar clutter.

12. The system of claim 9, wherein the communication signal has a duration one half the duration of the radar clutter.

13. The system of claim 9, wherein the communication signal is at least one of a preamble, a data symbol, or communication data.

14. The system of claim 9, wherein the radar clutter being based at least in part on a chirp modulation.

15. A radar system comprising a computer-readable storage medium comprising instructions that, when executed by a processor of the radar system, cause the processor to perform acts comprising:

receiving a signal comprising radar clutter and a communication signal;

generating a first subaperture comprising a first portion of the radar clutter;

generating a second subaperture comprising the communication signal and a second portion of the radar clutter, wherein the first subaperture has a same area as the second subaperture;

responsive to generating the first subaperture and the second subaperture, determining a signature of the first portion of the radar clutter;

filtering the second subaperture with the first portion signature to facilitate removal of the second portion of the radar clutter from the second subaperture;

extracting the communication signal from the second aperture based upon removing the second portion of the radar clutter from the second aperture;

determining a spectral estimation of the communication signal based upon the communication signal extracted from the second subaperture;

filtering the received signal with the communication signal spectral estimation, wherein the filtering removes from the received signal an artifact generated due to interference between the communication signal and the radar clutter; and

generating a radar image based upon the filtered received signal.

16. The radar system of claim 15, wherein the communication signal comprising at least one of a preamble, a data symbol, or communication data.

17. The radar system of claim 15, wherein the communication signal being configured to be transmitted for half of a duration of the radar signal.