INTERCARRIER SIGNAL DETECTION CIRCUIT FOR A TELEVISION RECEIVER

An intercarrier signal detection circuit for a television receiver sound system comprises a SAW (Surface Acoustic Wave) filter coupled to the output of a tuner, the SAW filter having a response characteristic including two symmetrical lobes centered about 41.25 MHz and 45.75 MHz respectively. The signal developed at the output of the SAW filter is applied to an AGC-controlled IF amplifier and then separated into a 41.25 MHz sound IF component and a 45.75 MHz picture IF component. The 41.25 MHz sound IF component is applied to one input of a synchronous detector whose other input is injected with a carrier signal developed by a phase lock loop operated in response to the 45.75 MHz picture IF component. The synchronous cetector thereby produces a relatively clean 4.5 MHz intercarrier sound signal which is preferably enhanced by causing the injected carrier signal to exhibit a quadrature phase relationship with any 45.75 MHz picture IF remnants characterizing the separated 41.25 MHz sound IF component. The 45.75 MHz picture IF component and an amplitude limited representation thereof developed by the phase lock loop, are coupled to respective inputs of an additional detector for developing a baseband video signal which is used by an AGC circuit for controlling the gain of the IF amplifier.