Patent ID: 7151577
Filing Date: 2006-12-19
Classification: H04N

Abstract:
1. A broadcast receiving system comprising: a high frequency amplifier circuit which receives and amplifies a broadcasting radio wave corresponding to a desired frequency and which provides an amplified output; a local oscillator circuit which produces and outputs in a PLL circuit a local oscillation signal having a local oscillation frequency corresponding to the desired frequency of the broadcasting radio wave; a mixing circuit which mixes the output provided from the high frequency amplifier circuit with the local oscillation signal provided from the local oscillator circuit to make conversion into an intermediate frequency signal and which outputs the intermediate frequency signal; a variable filter circuit which allows the intermediate frequency signal to pass therethrough, the variable filter circuit having a band-pass filter circuit which limits the frequency band of the signal passing therethrough and a switching circuit capable of switching whether the intermediate frequency signal outputted from the mixing circuit is to pass through or bypass the band-pass filter; an SAW filter which allows the intermediate frequency signal having passed through the variable filter circuit to pass therethrough; an intermediate frequency amplifier circuit for intermediate frequency amplification of the intermediate frequency signal having passed through the SAW filter; a VCO circuit which generates an oscillation signal and which can change the oscillation frequency of the oscillation signal; a detector circuit which, on the basis of the oscillation frequency of the oscillation signal, detects the intermediate frequency signal amplified by the intermediate frequency amplifier circuit and which outputs a video signal and an audio signal; and a microcomputer which, when receiving a broadcasting radio wave in voice FM broadcast, makes control for causing the switching circuit to switch over to the side where the intermediate frequency signal is allowed to pass through the band-pass filter circuit and for causing the VCO circuit to change the oscillation frequency of the oscillation signal into an oscillation frequency corresponding to the broadcasting radio wave in the voice FM broadcast.