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.