Multibeam single frequency synthetic aperture radar processor for imaging ...

United States Patent [19]

Jain

[ii] 4,355,311 [45] Oct. 19,1982

[54] MULTIBEAM SINGLE FREQUENCY
SYNTHETIC APERTURE RADAR
PROCESSOR FOR IMAGING SEPARATE
RANGE SWATHS

[76] Inventor: Robert A. Frosch, Administrator of the National Aeronautics and Space Administration, with respect to an invention of Atul Jain, La Canada, Calif.

[21] Appl. No.: 165,910
[22] Filed: Jul. 3, 1980

Related U.S. Application Data

[63] Continuation-in-part of Ser. No. 17,885, Mar. 6, 1979, abandoned.

[51] Int. CI.3 G01S 13/00; GO IS 13/90

[52] U.S. CI 343/5 CM; 343/9 PS;

367/88

[58] Field of Search 343/5 CM, 9 PS; 367/88

[56] References Cited

U.S. PATENT DOCUMENTS

3,184,736 5/1965 Badewitz 343/5 CM

3,191,170 6/1965 Lustig et al 343/5 CM

3,353,177 11/1967 Wilmot 343/5 VQ

3,548,642 12/1970 Flaherty et al 343/5 CM

3,560,973 2/1971 Kazel 343/5 CM

3,725,915 4/1973 Herman et al 343/5 CM

3,727,219 4/1973 Graham 343/5 CM

3,905,031 9/1975 McCord 343/5 CM

4,101,891 7/1978 Fletcher et al 343/5 CM

4,164,738 8/1979 Swerling 343/5 CM

4,184,154 1/1980 Albanese et al 343/9 R

OTHER PUBLICATIONS

C. Wu, "A Digital System To Produce Imagery From SAR Data", Proc. of AIAA Systems Design Driven By Sensors Conference, Paper No. 79-768, Oct. 18-20, 1976.

H. Jensen, et al., Scientific American, Oct. 1977, vol. 237, No. 4, pp. 84-95.

Primary Examiner—S. C. Buczinski

Attorney, Agent, or Firm—Monte F. Mott; John R.

Manning; Paul F. McCaul

[57] ABSTRACT

A single-frequency multibeam synthetic aperture radar for large swath imaging is disclosed. Each beam illuminates a separate "footprint" (i.e., range and azimuth interval). The distinct azimuth intervals for the separate beams produce a distinct Doppler frequency spectrum for each beam. After range correlation of raw data, an optical processor develops image data for the different beams by spatially separating the beams to place each beam of different Doppler frequency spectrum in a different location in the frequency plane as well as the imaging plane of the optical processor. Selection of a beam for imaging may be made in the frequency plane by adjusting the position of an aperture, or in the image plane by adjusting the position of a slit. The raw data may also be processed in digital form in an analogous manner.

15 Claims, 5 Drawing Figures