Abstract: A protective system for a vehicle-borne tracking radar, designed to counter the effect of an off-target jammer whose interfering signals are picked up by a directive antenna together with echoes from an actual target, comprises a receiver with a sum channel and a difference channel. In the absence of a jammer, the sum channel is connected via a signal processor to telemetric circuitry in the radar associated with the vehicular guidance system which keeps the antenna axis trained upon the target as the vehicle homes in on same. When a strong jamming signal is detected, a switching device in the processor cuts off the sum channel from the telemetric circuitry and supplies the latter, instead, with rectified error signals from the difference channel, these error signals being also delivered prior to rectification to a tracking-control circuit which energizes an antenna rotator to hold its axis in line with the jammer.

Abstract: An arrangement for protecting radars against unwanted echos such as "clutter" using an angular divergence measuring signal. This signal is compared with two predetermined thresholds + xo and - xo. When the probability of the two thresholds being exceeded by the divergence signal is greater than a predetermined value Po, the arrangement generates a logic signal which is used to prevent the tracking circuits of the radar from locking on to the received echo.

Abstract: The invention relates to an arrangement for suppressing the echos received in the side lobes of a main antenna of a radar system. An auxiliary antenna, whose diagram overlaps with the side lobes of the main antenna, supplies a signal B which is compared with the signal A from the main antenna. The comparison is performed between microwave signals or intermediate frequency signals by means of an operating circuit which emits signals S.sub.1 = A + k.sub.1 B and S.sub.2 = k.sub.2 (A - k.sub.1 B) where k.sub.1 and k.sub.2 are amplitude and phase modifying complex coefficients, and an amplitude and phase demodulating circuit which receives S.sub.1 and S.sub.2, one of which may possibly be in phase quadrature. The presence of an off-center echo, for example, results in a threshold being exceeded by the filtered demodulated signal.

Abstract: A band-compressor devices designed to match to one another two systems having different pass bands, comprises means for coding input signals in the form of N digital signals corresponding, at any instant, to the amplitude of the input signal with respect to N quantizing levels. N bistable trigger stages of RS or JK type, followed by as many D-type bistable stages, are provided to receive said digital signals on the one hand and pulses furnished by a clock on the other. The output signals from the bistable stages of type D are then recombined in an adder in order to furnish analog signals or in a coder for furnishing signals in binary form.

Abstract: A radar system emitting a recurrent sequence of n equispaced bursts of carrier frequency, varying from one burst to the next, has a transmitter including a carrier-frequency generator with a frequency-varying motor driven by a synchronizing circuit to produce a repetitive frequency pattern recurring a whole number of times in a program cycle of n pulse periods.