Ground clutter suppression technique
First Claim
1. In a pulsed Doppler radar, a ground clutter identification circuit comprising:
- a bifurcated parallel return signal processing circuit, one branch having a signal delay capability and both branches having linear-to-logarithmic conversion capability and respective outputs;
a deviation generator circuit for generating at least one deviation input functionally related to apparatus limitations for each signal received; and
means for summing said outputs of said processing circuit, coupled to both branches and to said deviation generator circuit.
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Abstract
A ground clutter suppression technique is disclosed utilizing two parallel return signal processing paths, both utilizing linear-to-logarithmic conversion capability and one having a signal delay capability for one pulse repetition. The outputs are subtracted and are subsequently compared with a factor related to the root-mean-square (rms) of two deviation inputs, one input functionally related to apparatus limitations and one deviation input functionally related to antenna position (step between samples) for each signal received. The Doppler frequency standard deviation inputs are then summed rms and used to select an amplitude standard deviation which is compared with the amplitude difference between successive return signals. Thereafter, the logic decision output is operated on utilizing a digital filter to essentially eliminate ground clutter or small variance (PRF to PRf) return signals from the display.
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Citations
17 Claims
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1. In a pulsed Doppler radar, a ground clutter identification circuit comprising:
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a bifurcated parallel return signal processing circuit, one branch having a signal delay capability and both branches having linear-to-logarithmic conversion capability and respective outputs; a deviation generator circuit for generating at least one deviation input functionally related to apparatus limitations for each signal received; and means for summing said outputs of said processing circuit, coupled to both branches and to said deviation generator circuit. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. In a pulsed Doppler radar, a ground clutter indication circuit comprising:
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a deviation generator for generating in parallel at least one deviation input functionally related to apparatus limitations for each signal received, and for generating at least one deviation input functionally related to antenna scan position and rate for each signal received; and means coupled to said deviation generator for summing and correlating said deviation inputs. - View Dependent Claims (9, 10, 11, 12, 13)
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14. A digital pulse radar apparatus for use with an antenna and having a ground clutter suppression circuit and a plurality of range cells comprising in combination:
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a. first means for receiving a first sequentially ordered plurality of returned signals, said signals received in a cyclic manner controlled by the pulse repetition rate of said apparatus; b. second means, coupled to said first means, for converting said first ordered plurality of signals from a linear to a logarithmic representation; c. third means, coupled to said first means, for delaying said first ordered plurality of signals for one pulse repetition; d. fourth means, coupled to said third means, for converting said delayed plurality of signals from a linear to a logarithmic representation; e. fifth means, coupled to said second means and to said fourth means, for summing said converted first ordered plurality of signals and said converted delayed plurality of signals; f. sixth means, coupled to said first means, for generating a signal deviation as a fixed function of the capability of said apparatus and providing a first deviation output; g. seventh means for coupling to said antenna and for generating a signal deviation as a variable function of antenna scan position, scan rate and antenna beamwidth for each of said plurality of range cells, and providing a second deviation output; h. an eighth means, coupled to said sixth means and to said seventh means, for summing said first deviation output and said second deviation output; i. ninth means, coupled to said eighth means, for correlating the Doppler frequency standard deviation of said summed deviations to the amplitude standard deviation; and j. tenth means, coupled to said fifth means and to said ninth means, for summing said summed converted signals with said summed deviations to provide binary outputs indicating which of said received signals exceed a predetermined threshold. - View Dependent Claims (15, 16, 17)
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Specification