Patent ID: 6633345
Filing Date: 2003-10-14
Classification: H04N

Abstract:
A receiver selectively receiving, demodulating, and outputting a television broadcast signal and an FM radio broadcast signal, the receiver comprising:a tuner which converts an FM radio broadcast signal to an intermediate frequency signal that has the same carrier frequency as a sound intermediate frequency subcarrier signal when receiving a television broadcast signal and outputs the intermediate frequency signal when receiving the FM radio broadcast signal; a band limit filter which passes only an intermediate frequency signal of a video intermediate frequency band of the television broadcast signal among intermediate frequency signals output by said tuner; an intermediate frequency amplifier which amplifies the intermediate frequency signal of the video intermediate frequency band output by said band limit filter; an oscillator which outputs a self-running oscillation signal having the same frequency as a video intermediate carrier signal of the video intermediate frequency band; a first switch selecting the video intermediate carrier signal output by said intermediate frequency amplifier when receiving the television broadcast signal and selecting the self-running oscillation signal when receiving the FM radio broadcast signal; a phase synchronizer which generates a signal that has a phase locked to the phase of one of the video intermediate carrier signal and the self-running oscillation signal selected by said first switch; a video detector which outputs one of a video signal containing a sound subcarrier signal and a sound subcarrier signal from the intermediate frequency signal of the video intermediate frequency band, amplified by said intermediate frequency amplifier, based on the signal output by said phase synchronizer; a sound band limit filter passing the sound subcarrier signal output by said video detector; a sound detector which detects and outputs one of a sound signal of the television broadcast signal and a sound signal of the FM radio broadcast signal based on the sound subcarrier signal output by said sound band limit filter; a first automatic gain controller which changes amplification of the intermediate frequency amplifier when receiving the television broadcast signal and controls the video signal output by said video detector to have a constant amplitude; a second automatic gain controller which changes the amplification of the intermediate frequency amplifier when receiving the FM radio broadcast signal and controls the sound subcarrier signal passed by said sound band limit filter to have a constant amplitude; and a second switch which selects between the control by the first automatic gain controller and control by the second automatic gain controller and outputs the control selected.