Radar receiver having clutter and large signal reduction

• US 3,916,408 A
• Filed: 01/18/1974
• Issued: 10/28/1975
• Est. Priority Date: 01/18/1974
• Status: Expired due to Term

• Current Assignee: Norol T. Evans, Richard F. Hyneman
• Original Assignee: Norol T. Evans, Richard F. Hyneman
• Inventors: Evans, Norol T., Hyneman, Richard F.
• Primary Examiner(s): Wilbur, Maynard R.
• Assistant Examiner(s): Berger, Richard E.
• Application Number:
  US05/436,270
• Time in Patent Office: 648 Days
• Field of Search: 343/1LE,1CL,18E
• US Class Current: 342/379
• 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 3/2629 Combination of a main antenna unit with an auxiliary antenna unit

Abstract

An improved radar receiver including coherent side-lobe cancellation in which a difference pattern is utilized in azimuth by the auxiliary antenna to reduce the clutter return signal on the auxiliary channel and to also cause the clutter signal to be decorrelated with the clutter received on the main antenna. The two effects of reducing the clutter return and the decorrelation considerably reduces the degradation in coherent side-lobe cancellation operation of jamming signals characteristically caused by clutter on the auxiliary channel over most of the surveillance volume. Also, by providing substantial attenuation of the large target return in the auxiliary channel by the null in the direction of the principle response of the main antenna, large target signal returns are unable to capture the coherent side-lobe canceller loops and inhibit the coherent cancellation of jamming signals.

Claims

1. A coherent radar receiver system responsive to target signals and jamming signals comprising:

main antenna means for receiving energy and having a predetermined lobe pattern along a reception axis;

auxiliary antenna means for receiving energy and having a pattern with a difference pattern symmetry relative to the reception axis of said main antenna means, said difference antenna pattern being centered at a null axis substantially parallel to the reception axis of said predetermined lobe pattern so clutter signals received from opposite sides of said null axis are decorrelated relative to clutter received by said main antenna means; and

coherent side lobe canceller means coupled to said main antenna means and to said auxiliary antenna means.

2. The receiver system of claim 1 in which said predetermined lobe pattern is a sum lobe pattern.

3. The receiver system of claim 2 in which said auxiliary antenna means is selected to develop a maximum gain pattern with peaks along the azimuth dimension that are less than the peak of a miximum gain pattern developed by said main antenna means.

4. The receiver system of claim 3 in which said auxiliary antenna means includes an antenna and a difference network coupled thereto.

5. A coherent radar receiver system responsive to target signals, jamming signals and clutter signals comprising:

a main receiver channel including main antenna means having a relatively narrow sum antenna beam along the antenna axis;

an auxiliary receiver channel including auxiliary antenna means having an axis substantially parallel and co-incident to the axis of said main antenna means and having a difference pattern substantially symmetrical and having a null on said axis; and

a coherent side-lobe canceller circuit coupled to said main and to said auxiliary receiver channels to cancel jamming signals.

6. The system of claim 5 in which said auxiliary antenna means includes an antenna and a difference network coupled thereto.

7. The system of claim 5 in which said auxiliary antenna means is selected to develop a maximum gain pattern with peaks along the azimuth dimension that are less than the peak of a maximum gain pattern developed by said main antenna means.