Arrangement for discriminating clutter signals from target signals in a radar system

Claim 2

In a radar system having an antenna, an arrangement for discriminating clutter reception signals from target reception signals, said arrangement comprising: means for supplying signals indicating the angular divergence between the direction from which are received said reception signals and at least one plane of symmetry of the antenna; means for generating two signals + xo and - xo of opposite sign; first comparing means for comparing said angular divergence signals with said signal + xo; first sampling and counting means for sampling and counting the output signals of said first comparing means; second comparing means for comparing said angular divergence signals with said signal - xo; second sampling and counting means for sampling and counting the output signals of said second comparing means; means for periodically resetting the first and second counting means to zero after a predetermined repetition period, and; means for producing a clutter presence signal when the contents of the two counting means both exceed a predetermined value during the said repetition period.

Claim 3

An arrangement according to claim 1, wherein the means for producing a clutter presence signal comprise an AND circuit which has two inputs connected respectively to the outputs of the first and second sampling and counting means, and an RS flip-flop circuit having an input connected to the output of the AND circuit and a zero-reset input connected to the output of the periodically resetting means.

Claim 4

An arrangement according to claim 1, wherein the first comparing means has a non inverting input which receives the said angular divergence signals and an inverting input which receives the threshold signal + xo and wherein the second comparing means has a non inverting input which receives the threshold signal - xo and an inverting input which receives the angular divergence signals.

Claim 5

An arrangement according to claim 1, further including a clock and a first counter for receiving pulses from said clock and wherein said first and second sampling and counting means each include a bistable flip-flop circuit of the RS type connected respectively to the first and second comparing means, the said flip-flop circuits having a zero reset input which receives the pulses from the clock, and a further counter which is connected respectively to the outputs of the flip-flop circuit, and further including means for resetting the said first, and further counters to zero when the first counter has reached its maximum capacity.

Claim 6

An arrangement according to claim 4, further comprising means for resetting each RS flip-flop to zero when one of the respective further counters has reached its maximum capacity.

Claim 7

In a radar system having an antenna, an arrangement for discriminating clutter reception signals from target reception signals, said arrangement comprising: means for supplying signals indicating the angular divergence between the direction from which are received said reception signals and at least one plane of symmetry of the antenna; first comparing means connected to said receiving means for comparing the said angular divergence signals with a first positive threshold + xo; first measuring means for measuring the probability P1 with which the threshold + xo is positively exceeded by said divergence signal, and second comparing means connected to said receiving means for comparing the said angular divergence signals with a second negative threshold + xo, second measuring means for measuring the probability P2 with which the threshold - xo is negatively exceeded by said divergence signal, and comparing means for comparing said probabilities P1 and P2 with a predetermined value Po, and means for producing a clutter presence signal when said probabilities P1 and P2 are simultaneously greater than Po.

Claim 8

In a radar system having an antenna, an arrangement for discriminating clutter reception signals from target reception signals, said arrangement comprising: means for supplying signals indicating the angular divergence between the direction from which are received said reception signals and at least one plane of symmetry of the antenna; first comparing means connected to said receiving means for comparing the said angular divergence signals with a first positive threshold + xo; first measuring means for measuring the probability P1 with which the threshold + xo is positively exceeded by said divergence signal, and second comparing means connected to said receiving means for comparing the said angular divergence signals with a second negative threshold + xo, second measuring means for measuring the probability P2 with which the threshold - xo is negatively exceeded by said divergence signal, and comparing means for comparing said probabilities P1 and P2 with a predetermined value Po, and means for producing a clutter presence signal when said probabilities P1 and P2 are simultaneously greater than Po.