Method and apparatus for reducing the effects of scintillation and rejection of clutter in monopulse radars

• US 4,296,415 A
• Filed: 02/06/1974
• Issued: 10/20/1981
• Est. Priority Date: 02/06/1974
• Status: Expired due to Term

• Current Assignee: Calspan Corp (Transdigm Group Incorporated)
• Original Assignee: Calspan Corp (Transdigm Group Incorporated)
• Inventors: Leney, Thomas F., Pelton, Frank M., Miller, Clyde A.
• Primary Examiner(s): Tubbesing, T. H.
• Application Number:
  US05/441,201
• Time in Patent Office: 2,813 Days
• Field of Search: 343/7 A, 343/16 M
• US Class Current: 342/94
• CPC Class Codes: G01S 13/4427 with means for eliminating the target-dependent errors in angle measurements, e.g. glint, scintillation effects

Abstract

A method and apparatus for processing monopulse radar return signals to synthesize the imaginary component (β_I) of the complex angle of arrival. Scintillation errors in the real component (β_R) of the complex angle of arrival can then be reduced on a pulse-by-pulse basis by the criterion that |β_I | be small in magnitude and gating the β_R signal when this criterion is not met.

Claims

1. A method for processing radar return signals in a four horn monopulse radar system for reducing rain, sea and land clutter, for reducing errors due to scintillation and for identifying tall, narrow structures having a much greater angular extent in the elevation plane than in the azimuth plane including the steps of:

processing the radar return signals to obtain signals representing the real part of the complex angle of arrival in the elevation and azimuth planes;

applying a first set of thresholds and processing the radar return signals to obtain signals indicative of the imaginary part of the complex angle of arrival in the elevation plane;

applying a second set of thresholds and processing the radar return signals to obtain signals indicative of the imaginary part of the complex angle of arrival in the azimuth plane;

processing the signals representing the real part of the complex angle of arrival in response to the thresholded signals indicative of the imaginary part of the complex angle of arrival whereby clutter and errors due to scintillation may be reduced and tall, narrow structures may be identified.

2. The method of claim 1 wherein tall, narrow structures will be identified from the radar return signals when the imaginary part of the complex angle of arrival in the elevation plane is greater than the first set of thresholds and the imaginary part of the complex angle of arrival in the azimuth plane is less than the second set of thresholds.

3. A circuit for processing radar return signals in a four horn monopulse radar system for reducing rain, sea and land clutter, for reducing errors due to scintillation and for identifying tall, narrow structures having a much greater angular extent in the elevation plane than in the azimuth plane including:

means for processing radar return signals to obtain signals representing the real part of the complex angle of arrival;

means for applying threshold levels and for processing radar return signals to obtain thresholded signals indicative of the imaginary part of the complex angle of arrival;

means for processing the signals representing the real part of the complex angle of arrival in response to the thresholded signals indicative of the imaginary part of the complex angle of arrival whereby clutter and errors due to scintillation may be reduced and tall, narrow structures may be identified.

4. A circuit for reducing rain, sea and land clutter and the errors introduced into radar return signals due to scintillation in a two horn monopulse radar system including:

first means for receiving and amplifying a first signal representing the vector sum of the signals in the two horns;

second means for receiving and amplifying a second signal representing the vector difference of the signals in the two horns;

amplitude detector means for receiving the amplified first signal and producing an output signal;

first phase detector means for receiving the amplified first signal as a first input and the amplified second signal as a second input and producing an output signal;

divider means for receiving the output signal of the amplitude detector means as a first input and the output signal of the first phase detector means as a second input and producing a signal representing the real component of the complex angle of arrival;

phase shifting means for receiving as an input the amplified second signal and producing an output signal;

second phase detector means for receiving as a first input the amplified first signal and as a second input the output signal of the phase shifting means and for producing an output signal;

means for receiving the output signal of the amplitude detector as a first input and the output of the second phase detector and as a second input and for producing an output signal indicative of the imaginary component of the complex angle of arrival;

gating means for gating the signal representing the real component of the complex angle of arrival in response to the signal indicative of the corresponding imaginary component of the complex angle of arrival whereby each and every range cell of the received real part of the complex angle of arrival is sorted on a pulse-by-pulse basis so that only the more reliable data is retained which results in the producing of a more accurate target location and the reduction of clutter returns from angularly spread complex targets.

5. A circuit for processing radar return signals in a four horn monopulse radar system for reducing rain, sea and land clutter, for reducing errors due to scintillation and for identifying tall, narrow structures having a much greater angular extent in the elevation plane than in the azimuth plane including:

first means for receiving and amplifying a first signal representing the vector sum of the signals in the four horns;

second means for receiving and amplifying a second signal representing the vector difference in the elevation plane;

third means for receiving and amplifying a third signal representing the vector difference in the azimuth plane;

amplitude detector means for receiving the amplified first signal and producing an output signal;

first phase detector means for receiving the amplified first signal as a first input and the amplified second signal as a second input and producing an output signal;

first divider means for receiving the output signal of the amplitude detector means as a first input and the output signal of the first phase detector means as a second input and producing a signal representing the real component of the complex angle of arrival in the elevation plane;

first phase shifting means for receiving as an input the amplified second signal and producing an output signal;

second phase detector means for receiving as a first input the amplified first signal and as a second input the output signal of the first phase shifting means and for producing an output signal;

third phase detector means for receiving as a first input the amplified first signal and the amplified third signal as a second input and producing an output signal;

second phase shifting means for receiving as an input the amplified third signal and producing an output signal;

fourth phase detector means for receiving as a first input the amplified first signal and as a second input the output signal of the second phase shifting means and for producing an output signal;

second divider means for receiving the output signal of the amplitude detector means as a first input and the output signal of the third phase detector means as a second input and producing a signal representing the real component of the complex angle of arrival in the azimuth plane;

first comparator means for receiving the output signal of the amplitude detector means as a first input and the output signal of the second phase detector means as a second input and producing an output signal indicative of the imaginary component of the complex angle of arrival in the elevation plane;

second comparator means for receiving the output signal of the amplitude detector means as a first input and the output signal of the fourth phase detector means as a second input and producing an output signal indicative of the imaginary component of the complex angle of arrival in the azimuth plane; and

means for processing the output signals of the first and second divider means responsive to the output signals of the first and second comparator means whereby clutter and errors due to scintillation may be reduced and tall, narrow structures may be identified.