Method and system for sharpening impulse response in a synthetic aperture radar

• US 5,334,980 A
• Filed: 08/02/1993
• Issued: 08/02/1994
• Est. Priority Date: 08/02/1993
• Status: Expired due to Fees

• Current Assignee: Northrop Grumman Corporation
• Original Assignee: Westinghouse Electric Company LLC (Brookfield Asset Management Incorporated)
• Inventors: Decker, Martin J.
• Primary Examiner(s): Barron, Jr., Gilberto
• Application Number:
  US08/100,825
• Time in Patent Office: 365 Days
• Field of Search: 342/25
• US Class Current: 342/25.00C
• CPC Class Codes: G01S 13/9092 combined with monopulse techniques

Abstract

A synthetic aperture radar system performing two dimensional monopulse measurement of the return data.

Claims

1. A method of sharpening impulse response of synthetic aperture return data of a synthetic aperture radar system, comprising:

collecting computed range and azimuth return data;

forming three apertures of the collected computed data, one of the three apertures generating data corresponding to SUM weighting in range and azimuth, a second of the apertures generating data corresponding to SUM weighting in range and DELTA weighting in azimuth, and a third of the apertures generating data corresponding to SUM weighting in azimuth and DELTA weighting in range;

transforming the generated data in each of the three apertures into a two dimensional map format;

performing two dimensional monopulse measurement of a combined transformed generated data in the map format, having bins corresponding to range and azimuth;

calculating the DELTA data in range and the DELTA data in azimuth for each of the bins; and

displaying the return energy in the individual range and azimuth bins in accordance with a monopulse measurement ratio of the SUM data of the range and the DELTA data of the range in the range bins and a ratio of the SUM data of the azimuth and the DELTA data of the range in each azimuth bin.

2. The method of claim 1 wherein the step of performing the monopulse measurement in two dimension comprises:

computing the power of the SUM data in range and azimuth, the DELTA data in range, and the DELTA data in azimuth, for the respective apertures;

comparing the power of the DELTA data in azimuth and the DELTA data in range with the power of the SUM data in range and azimuth; and

setting the respective DELTA data in range and azimuth to zero at times when the corresponding DELTA data is greater than a predetermined amount above the power of the SUM data.

3. The method of claim 1 wherein the step of performing the monopulse measurement in two dimensions comprises:

computing for each return cell the monopulse measurement of range in accordance with the expression ##EQU3## computing for each return cell the monopulse measurement of azimuth in accordance with the expression ##EQU4## where Δ

A is the DELTA azimuth data Δ

R is the DELTA range data; and

Σ

is the SUM data.

4. The method of claim 3 wherein the step of performing monopulse measurement includes;

shifting the transformed DELTA path in the map format to selected bins in accordance with the computed monopulse measurement in range and azimuth.

5. The method of claim 3 wherein the step of performing monopulse measurement includes converting monopulse measurement to specific Δ

R bins and Δ

A bins in accordance with a look up table.

6. The method of claim 1 wherein the step of performing the monopulse measurement includes calculating off boresight angles in accordance with a ratio of the SUM and DELTA data.

7. A synthetic aperture radar system, comprising:

means for collecting complex range and azimuth return data during each look of the synthetic aperture antenna;

means for storing the collected data in three memories;

means including the three memories including the three memories for generating data corresponding to sum weighting in range and azimuth, sum weighting in range and delta weighting in azimuth, and sum weighting in azimuth and delta weighting in range;

means for transforming the generated data in each of the three memories into a two dimensional map format;

means for performing two dimensional monopulse measurement of combined transformed generated data in the map format, the map format including bins corresponding to range azimuth;

means for calculating the DELTA data in range and the DELTA data in azimuth for each of the bins; and

displaying the return energy in the individual range and azimuth bins in accordance with the ratio of the SUM data in range and the DELTA data in range in the range bins, and a ratio of the SUM data in azimuth and the DELTA data in range in each azimuth bin.

8. The system of claim 7 wherein the means for performing the monopulse measurement in two dimensions comprises,

means for computing the power of the SUM data in range and azimuth, the DELTA data in range, and the DELTA data in azimuth, for the respective memories;

means for comparing the power of the DELTA data in azimuth and the DELTA data in range with the power of the SUM data in range and azimuth; and

setting the respective DELTA data in range and azimuth to zero at times when the corresponding DELTA data is greater than a predetermined amount above the power of the SUM data.

9. The system of claim 7 wherein the means for performing the monopulse measurement comprises:

means for computing the monopulse measurement of range in accordance with the expression ##EQU5## and means for computing the monopulse measurement of azimuth in accordance with the expression ##EQU6## where ∇

A is the azimuth DELTA, Δ

R is the range DELTA data and Σ

is the SUM data.

10. The system of claim 9 wherein the means for performing monopulse measurement comprises means for shifting the transformed DELTA data in the map format to selected bins in accordance with the computed monopulse measurement in range and azimuth.

11. The system of claim 9 wherein the means for performing monopulse measurement comprises means for converting the monopulse measurement to specific Δ

R bins and specific Δ

A bins in accordance with a look up table.

12. The system of claim 7 wherein the means for performing the monopulse measurement includes means for calculating off boresight angles in accordance with the ratio of the SUM and DELTA data.