Method and system for moving target elimination and indication using smoothing filters
First Claim
1. In a monopulse radar system, a null command generator fed by the in-phase and quadrature sum and difference signals derived from target reflections received at monopulse antennas comprising:
- a. a first subtracting circuit fed by the in-phase sum and difference signals;
b. a second subtracting circuit fed by the quadarature sum and difference signals;
c. a first summing circuit fed by the in-phase sum and difference signals;
d. a second summing circuit fed by the quadrature sum and difference signals;
e. a third summing circuit fed by the first and second subtracting circuits;
f. a fourth summing circuit fed by the first and second summing circuits;
g. means for delaying the output of the third summing circuit by a time value τ
d, where τ
d is a value equal to the distance between the antenna phase center divided by the product of 4 times the product of the aircraft velocity and the target azimuth;
h. means for advancing the output of the fourth summing circuit by τ
d ;
i. a first bank of narrow band filters fed by the delaying means;
j. a second bank of narrow band filters identical to that of the first bank fed by the advancing means;
k. means for phase differencing corresponding filters of the first and second banks of narrow band filters;
l. a plurality of means for smoothing the outputs of the phase differencing means; and
m. means for averaging the outputs of the smoothing means.
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Abstract
In-phase sum and difference signals and quadrature sum and difference signals from a monopulse radar system are processed to form the sum of the in-phase signals, the sum of the quadrature signals, the difference of the in-phase signals, and the difference of the quadrature signals. The processed sum signals and the processed difference signals are then combined to form complex signals one of which is advanced and the other retarded by pedetermined time. The complex signals are then divided into sequences of frequencies of identical banks of narrow band filters. The differences between the outputs of corresponding filters from each bank are smoothed by low pass filters, averaged and then divided by a constant to form a beam pointing error value.
16 Citations
7 Claims
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1. In a monopulse radar system, a null command generator fed by the in-phase and quadrature sum and difference signals derived from target reflections received at monopulse antennas comprising:
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a. a first subtracting circuit fed by the in-phase sum and difference signals; b. a second subtracting circuit fed by the quadarature sum and difference signals; c. a first summing circuit fed by the in-phase sum and difference signals; d. a second summing circuit fed by the quadrature sum and difference signals; e. a third summing circuit fed by the first and second subtracting circuits; f. a fourth summing circuit fed by the first and second summing circuits; g. means for delaying the output of the third summing circuit by a time value τ
d, where τ
d is a value equal to the distance between the antenna phase center divided by the product of 4 times the product of the aircraft velocity and the target azimuth;h. means for advancing the output of the fourth summing circuit by τ
d ;i. a first bank of narrow band filters fed by the delaying means; j. a second bank of narrow band filters identical to that of the first bank fed by the advancing means; k. means for phase differencing corresponding filters of the first and second banks of narrow band filters; l. a plurality of means for smoothing the outputs of the phase differencing means; and m. means for averaging the outputs of the smoothing means. - View Dependent Claims (2, 4, 6)
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3. d. a second bank of means for obtaining the square of the absolute value of the outputs of the first bank of narrow band filters;
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e. a third bank of means for obtaining the square of the absolute value of the outputs of the second bank of filters; f. means for adding the outputs of corresponding absolute value squaring means of the second and third banks thereof; g. a bank of means for multiplying a constant to the output of the bank of adding means forming a threshold signal; h. means or comparing the threshold signals with the corresponding output of the first bank of absolute squaring means for selection control, the output of the comparing means being fed to the averaging means; and i. means for dividing the output of the averaging means by a value equal to the product of π
times the distance between the phase centers of the antennas divided by the wavelength of the radar signal.
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5. A method of generating an error signal from inphase and quadrature sum signals and in-phase and quadrature difference signals derived from a monopulse radar system comprising:
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a. subtracting the in-phase signals forming a first difference; b. adding the in-phase signals forming a first sum; c. subtracting the quadrature signals forming a second difference; d. adding the quadrature signals forming a second sum; e. adding the first and second sums forming a first complex signal; f. adding the first and second differences forming a second complex signal; g. advancing the first complex signal by a predetermined value; h. delaying the second complex signal by said predetermined value; i. narrow band filtering the delayed complex signal into a first sequence of frequency bands; j. narrow band filtering the advanced complex signal into a second sequence of frequency bands corresponding to the first sequence; k. phase differencing the signals from corresponding frequency bands of the first and second sequences forming a sequence of phase difference signals; l. smoothing each of the sequence of the phase difference signals; and m. averaging the smoothed phase difference signals. - View Dependent Claims (7)
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Specification