An apparatus for suppressing noise pulses in a impulsdopplerradars receiver.

摘要

1490751 Radar TELEFONAKTTEBOLAGET L M ERICSSON 10 Jan 1975 [15 Jan 1974] 1205/75 Heading H4D In a pulse Doppler radar, of the type wherein the echo signals are quadrature phase detected to give quadrature signals i, q. circuitry to stop large amplitude interference being passed to further processing circuitry, comprises an amplitude former 7 receiving the quadrature signals and producing a signal (comparison signal) representing the amplitude of the echo signal, and a comparator 8 comparing the 'comparison signal' instantly occurring with that which was produced from a previous echo period and causing the operation of switches 4, 4SP1/SP such that the instant signal is blocked, when the instant comparison signal is significantly larger than the previous comparison signal. The digital quadrature signal i, is first filtered at 1, and then passed to a circuit 4, 5, 6 comprising the twoway switch 4a, one p.r.p. delay 5 and an adder 6 which gives (with switch 4 in the position shown) signal i 1 , being the sum of the instant quadrature signal and that of the previous p.r.p., which sum signal i 1 used for the amplitude former 7 is freer from ground echo interference. The output from comparator 8 switches over switch 4 and also a switch 9 such that with interference being received, the comparison signal which is tapped to the upper input of the comparator is continuously the last received non-interference or low comparison signal. Likewise the provision of delay 5 and the closed loop formed by switch 4 ensures that it is the last received low quadrature signal which is continuously fed to the processing circuits. The amplitude of the instant comparison signal may be monitored in a threshold detector 10 to provide an output signal which, together with the comparator output, enables an AND gate 12. The amplitude former may perform either of the calculations: