Sea clutter suppression radar

• US 4,928,131 A
• Filed: 09/07/1988
• Issued: 05/22/1990
• Est. Priority Date: 09/17/1987
• Status: Expired due to Term

• Current Assignee: OKI Electric Industry Company Limited
• Original Assignee: OKI Electric Industry Company Limited
• Inventors: Onozawa, Kazuo
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): Sotomayor, John B.
• Application Number:
  US07/241,236
• Time in Patent Office: 622 Days
• Field of Search: 342/188, 342/159
• US Class Current: 342/188
• CPC Class Codes: G01S 7/024 using polarisation effects in waveguides H01P1/165; for aerials H01Q, e.g. H01Q15/22, H01Q15/24, H01Q19/195

Abstract

A sea clutter suppression radar is capable of effectively suppressing the reflected signal using RF waves of a single frequency by simultaneously sending the RF waves each having horizontal and vertical polarizations, and detecting, from a reflected signal from a target, horizontally and vertically polarized components and the vector sum and the vector difference signals between these components, and then processing these signals to suppress the reflected signal from the sea surface. The radar includes at least one antenna for simultaneously sending horizontally and vertically polarized RF waves, first and second detectors each for detecting intermediate frequency signals or horizontally and vertically polarized components of reflected RF waves, third and fourth detectors each for detecting IF signals of the vector sum and vector difference between the horizontally and vertically polarized components and a polar signal generator for generating a polar signal based upon the difference between the addition of both outputs of the first and second detectors, and the absolute value of the difference between said both outputs and the difference between the outputs of the third and fourth detectors.

Claims

1. Sea clutter suppression radar comprising:

(a) at least one antenna for simultaneously sending horizontally and vertically polarized RF waves;

(b) first and second detectors for respectively detecting IF signals of horizontally and vertically polarized components of reflected RF waves and for providing outputs corresponding thereto;

(c) third and fourth detectors for respectively detecting IF signals of the vector sum and vector difference between said horizontally and vertically polarized components and for providing outputs corresponding thereto;

(d) a first subtracter for subtracting an absolute value of a difference between said outputs from said first and second detectors, from a sum of said outputs from said first and second detectors;

(e) a second subtracter for subtracting said output from said fourth detector, from said output from said third detector;

(f) a polarity signal generator for generating an output which is a binary signal according to a selected logic combination of results of a plurality of comparisons between;

(1) each of a plurality of voltages proportional to a fraction of said output of said first subtracter and a plurality of voltages proportional to a fraction of an inverted output of said first subtracter and;

(2) said output from said second subtracter;

(g) a first means for providing an output equal to an absolute value of a difference between said outputs of said first and second detectors;

(h) a third subtracter for providing an output equal to a difference between said output of said first means and said output of said third detector;

(i) a fourth subtracter for providing an output equal to a difference between said output of said first means and said output of said fourth detector;

(j) an adder for adding said outputs of said third and fourth subtracters; and

(k) a polarity conversion circuit for selectively converting a polarity of an output from said adder in accordance with said output from said polarity signal generator.

2. Sea clutter suppression radar comprising:

(a) at least one antenna for simultaneously sending horizontally and vertically polarized RF waves;

(b) first and second detectors for respectively detecting IF signals of horizontally and vertically polarized components of reflected RF waves;

(c) third and fourth detectors for respectively detecting IF signals of the vector sum nd vector difference between said horizontally and vertically polarized components;

(d) a first subtracter for subtracting an absolute value of a difference between said outputs from said first and second detectors, from a sum of said outputs from said first and second detectors;

(e) a second subtracter for subtracting said output from said fourth detector, from said output from said third detector;

(f) a polarity signal generator for generating an output which is a binary signal according to a selected logic combination of results of a plurality of comparisons between;

(1) each of a plurality of voltages proportional to a fraction of said output of said first subtracter and a plurality of voltages proportional to a fraction of an inverted output of said first subtracter and;

(2) said output from said second subtracter;

(g) a first means for providing an output equal to an absolute value of a difference between said outputs of said first and second detectors;

(h) a third subtracter for providing an output equal to a difference between said output of said first means and said output of said third detector;

(i) a fourth subtracter for providing an output equal to a difference between said output of said first means and said output of said fourth detector;

(j) an adder for adding said outputs of said third and fourth subtracters;

(k) a mean level elimination circuit for subtracting a DC value from said output of said adder; and

(l) a polarity conversion circuit for selectively converting a polarity of an output of said mean level elimination circuit in accordance with said output from said polarity signal generator.

3. A sea clutter suppression radar according to claim 2, wherein said mean level elimination circuit includes delay circuits, filter and subtracters.

4. A sea clutter suppression radar according to claim 2, wherein said polarity conversion circuit includes switching circuits.