Patent ID: 7860479

Claim:
An FM receiver, comprising: an intermediate signal generating circuit for subjecting a reception signal to frequency conversion in which a carrier frequency of a received target FM signal is shifted to a predetermined intermediate frequency, and generating an intermediate signal; a bandpass filter for allowing a transmission bandwidth to be variably set, and transmitting the received target FM signal that has been converted to the intermediate signal; a detection circuit for subjecting the received target FM signal that has passed through the bandpass filter to detection, and generating a detection output signal; a bandwidth controller for controlling the transmission bandwidth of the bandpass filter; a strength signal generating circuit for generating, on the basis of the intermediate signal, an electric field strength signal according to the strength of a reception electric field; and a fluctuation component signal generating circuit for generating a fluctuation component signal according to fluctuation in an amplitude of the intermediate signal; wherein the bandwidth controller comprises: a high-pass filter, which has a cut-off frequency that exceeds an audio band; a switch circuit for selecting either the detection output signal or the fluctuation component signal according to the electric field strength signal, and inputting the selected signal to the high-pass filter; and a control circuit for controlling the transmission bandwidth on the basis of whether a weak high-pass component state or a strong high-pass component state is in effect, with the weak high-pass component state occurring when the output level of the high-pass filter is equal to or less than a predetermined reference value, and the strong high-pass component state occurring when the output level exceeds the reference value; wherein the switch circuit outputs the fluctuation component signal when the reception electric field strength is in a predetermined weak electric field state, and outputs the detection output signal when the reception electric field strength exceeds the weak electric field state; and the control circuit sets the transmission bandwidth to a predetermined wide bandwidth in the weak high-pass component state, and sets the transmission bandwidth to a narrow bandwidth, which is narrower than the wide band width, in the strong high-pass component state.