Low angle radar processing means

• US 4,316,191 A
• Filed: 04/14/1980
• Issued: 02/16/1982
• Est. Priority Date: 04/14/1980
• Status: Expired due to Term

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: The Bendix Corporation (Honeywell International Inc.)
• Inventors: Sawatari, Takeo, Mueller, Rolf K., Keating, Patrick N., Steinberg, Ronald F.
• Primary Examiner(s): Tubbesing, T. H.
• Application Number:
  US06/140,032
• Time in Patent Office: 673 Days
• Field of Search: 343/5 NQ, 343/16 R, 343/16 M
• US Class Current: 342/91
• CPC Class Codes: G01S 3/10 Means for reducing or compensating for quadrantal, site, or like errors
• CPC Class Codes: G01S 7/28 Details of pulse systems

Abstract

The elevation angle of a low angle target is accurately measured by subtracting from the received radar signal signals derived from an estimated value of target elevation which reduces the resulting signal to a minimum. The estimated value is an accurate measure of target elevation.

Claims

1. Radar equipment for processing electromagnetic signals from a low elevation target including radar means for receiving said electromagnetic signals from said low elevation target directly and via ground bounce comprising:

an N element array antenna for receiving said electromagnetic signals;

a set of N detectors of the received electromagnetic signals, each said detector being arranged in a separate channel;

demodulator means for converting the detected electromagnetic signals into a set of N complex electrical signals X_m, one said electrical signal being contained in each said channel;

a matrix of complex weights M_mn responsive to said set of N complex electrical signals X_m for generating a set of N complex electrical signals X_n '"'"' where;

##EQU8## means for determining the total power represented by said set of N complex electrical signals X_n '"'"'; and

,

means for iteratively adjusting said complex weights M_mn to minimize said total power.

2. The equipment of claim 1 wherein:

##EQU9## where r and s correspond to the elevation angles of two signals from said low elevation target, respectively the direct-path signal (r, s=1) and the ground multipath signal (r, s=2) so that the set of H_rs values (H₁₁, H₁₂, H₂₁, H₂₂) forms a 2×

2 matrix H, the inverse of which is;

##EQU10## and wherein;

##EQU11## λ

=the wavelength of the electromagnetic signals A_n is the position of the n^th detector, and the normalized complex amplitude of the electromagnetic signals incident on the n^th detector due to said low elevation target at an angle θ

_s is defined as d_sn where;

##EQU12## and, wherein said complex weights are factorable into a real weighting factor W_mn and a real phase shift φ

_mn, said matrix being comprised of means for weighting said complex electrical signals by W_mn and for shifting the phase thereof by φ

_mn.

3. The equipment of claim 1 or 2 wherein said means for determining the total power represented by said set of N complex electrical signals X_n '"'"' comprises:

means for squaring each of the signals X_n '"'"' to produce a set of power signals, each of which represents the power content of its parent signal X_n '"'"'; and

,

means for summing said power signals.

4. The equipment of claim 1 or 2 wherein said means for determining the total power represented by said set of N complex electrical signals X_n '"'"' comprises:

means for summing said N complex electrical signals X_n '"'"'; and

,

means for squaring the sum of said N complex electrical signals X_n '"'"'.