Abstract 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.
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 decrease with the distance to the targets, the arrangement comprising: a pulse generator; a pulse transmitter controlled by said pulse generator; a transmitter antenna connected to said pulse transmitter; an onoff circuit controlled by said pulse generator which emits to the on-off circuit an on pulse in conjunction with the termination of each transmitted pulse; and a low-pass filter having an output connected to the input of said on-off circuit and having an input connected to the output of the receiver part of the arrangement, the low-pass filter increasing the duration of the trailing edge of the received pulse for causing a compensation of the distancedependent amplitude of the output signal of the on-off circuit for reflections directly from targets, so that the sensitivity of the arrangement is in the main constant within said range and in the main equal to zero outside said range.
Claim 2
Dependent Claim
176 words
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 decrease with the distance to the targets, the arrangement comprising: a pulse generator; a pulse transmitter controlled by said pulse generator; a transmitter antenna connected to said pulse transmitter; an onoff circuit controlled by said pulse generator which emits to the on-off circuit an on pulse in conjunction with the termination of each transmitted pulse; and a low-pass filter having an output connected to the input of said on-off circuit and having an input connected to the output of the receiver part of the arrangement, the low-pass filter increasing the duration of the trailing edge of the received pulse for causing a compensation of the distancedependent amplitude of the output signal of the on-off circuit for reflections directly from targets, so that the sensitivity of the arrangement is in the main constant within said range and in the main equal to zero outside said range.
Claim 3
Dependent Claim
23 words
Arrangement according to claim 1, the on-off circuit being kept on during a time which is essentially shorter than the transmitter pulse width.
Claim 4
Dependent Claim
42 words
Arrangement according to claim 1 wherein the pulse transmitter is so constituted, that the transmitted pulse has a gradually decreasing amplitude, whereby a further compensation of the distanCe dependence of the signal obtained at the output of the on-off circuit is obtained.