DK130558C

Transmitter- and receiver arrangement for detection of targets situated within a limited range next to the arrangement by means of transmitted and target reflected pulses, whereby the amplitude of the reflected pulses decreases with the distance to the target. A pulsed transmitter is connected to the transmitter antenna of the transmitter and receiver arrangement and is controlled from a pulse generator so that pulses are fed periodically to the transmitter antenna. The pulse generator also controls an on-off circuit in the receiver part of the arrangement, the input of which circuit via a low-pass filter is connected to a receiver which in its turn is connected to a receiver antenna. During a certain short time interval in conjunction with the trailing edge of the transmitted pulse the pulse generator opens the on-off circuit allowing a received signal to be fed to the signal processing circuit of the receiver. By selecting the cut-off frequency of the low-pass filter and the time interval during which the gate is open in a suitable manner a compensation of the distance dependent amplitude of the echo signal can be achieved.