Abstract: A noise reducing circuit for a receiver such as an FM receiver which is improved in noise reducing effect while reducing an unfamiliar feeling to and an erroneous operation of the receiver. The noise reducing circuit comprises fuzzy inference means for fuzzy inferring, using an input vector consisting of several factors defining a receiving input condition as a prerequisite, in accordance with fuzzy production rules provided by membership functions of the factors of the input vector, and a fuzzy controlling signal generating circuit for generating a fuzzy controlling signal for controlling a control object amount of any one of a separation control circuit, a frequency characteristic control circuit and muting circuit or each of any combination of the circuits in accordance with a result of inference produced by the fuzzy inference means.

Abstract: A noise suppressing circuit has a gate for controlling a composite signal applied to a stereo demodulator of an FM tuner, and a detector for detecting a noise included in the composite signal and for producing a noise dependent signal for controlling the gate to close it. A pilot signal detector is provided for detecting a pilot signal included in the composite signal for producing a pilot dependent pulses. In response to the noise dependent signal and to the pilot dependent pulses, gate control pulses are applied to the gate, thereby closing the gate in synchronism with the pilot signal.

Abstract: A multipath detector circuit is in a form of a differential amplifier and has a first level dependent on strength of a received signal and a second level set to a lower level than the first level. The circuit produces a multipath level signal when the first level reduces below a threshold represented by a difference between the first level and the second level increases with an increase of the first level. The multipath detector circuit is arranged so that the threshold increases with an increase of the first level.