Receiver and transmitter-receiver having variable attenuator to avoid

Abstract

There are provided a receiver and a transmitter-receiver in which an automatic gain control loop is promptly performed and even in the case of a modulated wave having information in its amplitude, wave distortion can be eliminated. A received signal is received by an antenna and is amplified by a power amplifier. The gain of the received signal is attenuated by a variable attenuator in accordance with an output voltage of a holding circuit. After the signal is converted to an intermediate-frequency signal and amplified through a common procedure and detected, a comparator compares an output signal of the detector and a reference voltage V.sub.ref, and obtains a signal indicating whether the output signal exceeds a reference voltage or a differential voltage therebetween. When the output signal or the differential voltage is brought to a positive level, a timing signal generating section generates a timing signal T.sub.m, and the holding circuit holds a detection signal. In the variable attenuator, the signal is attenuated in accordance with the detection signal. Thereafter, output of the detector is integrated in a time constant circuit, and addition of respective outputs of the time constant circuit and the holding circuit is performed in a computing unit.