Intercarrier signal detection circuit for a television receiver

In a television receiver having a tuner responsive to a received television signal for developing an IF signal including a sound IF component comprising a frequency modulated sound carrier and a picture IF component comprising an amplitude modulated picture carrier, an improved sound processing circuit comprising:

• filter means receiving said IF signal for developing a single filtered IF output signal comprising a representation of said sound IF component symmetrically processed about said sound carrier and a representation of said picture IF component symmetrically processed about said picture carrier;
• means for controllably amplifying said single filtered IF output signal;
• means for separating said amplified single filtered IF output signal into first and second signals, said first signal comprising said symmetrically processed representation of said picture IF component and said second signal comprising said symmetrically processed representation of said sound IF component, said second signal including an attenuated form of said symmetrically processed representation of said picture IF component;
• automatic gain control means receiving said first signal for controlling the gain of said amplifying means;
• a synchronous detector;
• signal generating means receiving said first signal for generating a substantially unmodulated reference signal having a frequency substantially equal to said picture carrier and a phase substantially in quadrature relationship with the phase of said attenuated form of said picture IF component characterizing said second signal;
• and
• means for coupling said second signal and said reference signal to respective inputs of said synchronous detector for developing an intercarrier sound signal.

In a television receiver including means developing an IF signal including a symmetrically processed picture IF component and a sound IF component and an IF amplifier processing said IF signal for equally amplifying said picture and sound IF components, an improved sound processing circuit comprising:

• signal generating means responsive to said amplified IF signal for generating a reference signal having a frequency substantially equal to the frequency of the carrier of said picture IF component;
• automatic gain control means responsive to said amplified IF signal for developing a control signal for controlling the gain of said IF amplifier;
• a synchronous detector;
• and
• means for coupling said reference signal and said amplified IF output signal to respective inputs of said synchronous detector for developing an intercarrier sound signal.

In a television receiver including means developing an IF signal including a symmetrically processed picture IF component and a sound IF component, an IF amplifier processing said IF signal for equally amplifying said picture and sound IF components and means for separating said amplified IF signal into first and second signals, said first signal comprising said amplified picture component and said second signal comprising said amplified sound component and an attenuated representation of said amplified picture component, an improved sound processing circuit comprising:

• signal generating means receving said first signal for generating a substantially unmodulated reference signal having a frequency substantially equal to the carrier of said picture IF component and a phase substantially in quadrature relationship with the phase of said attenuated representation of said amplified picture component;
• automatic gain control means responsive to said first signal for developing a control signal for controlling the gain of said IF amplifier;
• a synchronous detector;
• and
• means for coupling said reference signal and said second signal to respective inputs of said synchronous detector for developing an intercarrier sound signal.

A television receiver comprising:

• tuning means for developing an IF signal having a sound IF component comprising a frequency modulated sound carrier and a picture IF component comprising an amplitude modulated picture carrier;
• first IF means responsive to said IF signal for developing a vestigial sideband compensated IF signal;
• detecting means having a first input connected for receiving said vestigial sideband compensated IF signal;
• second IF means responsive to said IF signal and having a symmetrical response centered about said picture carrier and having a response centered about said sound carrier for developing a symmetrically processed IF signal;
• means for controllably amplifying said symmetrically processed IF signal;
• a synchronous detector;
• means coupling the output of said amplifying means to a first input of said synchronous detector;
• automatic gain control means responsive to said amplified symmetrically processed IF signal for controlling the gain of said amplifying means;
• signal generating means receiving said amplified symmetrically processed IF signal for generating a first reference signal having a frequency substantially equal to the frequency of said picture carrier and a phase substantially in quadrature relationship with the phase of the picture component of said amplified symmetrically processed IF signal and a second reference signal having a frequency substantially equal to the frequency of said picture carrier and a phase in substantial alignment with the phase of said vestigial sideband compensated IF signal;
• and
• means coupling said first reference signal to a second input of said synchronous detector for developing an intercarrier sound signal and coupling said second reference signal to a second input of said detecting means for developing a composite baseband video signal.

A television receiver comprising:

• tuning means for developing an IF signal having a sound IF component comprising a frequency modulated sound carrier and a picture IF component comprising an amplitude modulated picture carrier;
• first IF means responsive to said If signal for developing a vestigial sideband compensated IF signal;
• detecting means having a first input connected for receiving said vestigial sideband compensated IF signal;
• second IF means receiving said IF signal for developing a single filtered IF output signal comprising a representation of said sound IF component symmetrically processed about said sound carrier and a representation of said picture IF component symmetrically processed about said picture carrier;
• means for controllably amplifying said single filtered IF output signal;
• means for separating said amplified single filtered IF output signal into first and second signals, said first signal comrising said symmetrically processed representation of said picture IF component and said second signal comprising said symmetrically processed representation of said sound IF component;
• automatic gain control means receiving said first signal for controlling the gain of said amplifying means;
• a synchronous detector;
• signal generating means receiving said first signal for generating substantially unmodulated first and second reference signals each having a frequency substantially equal to said picture carrier;
• and
• means coupling said second signal and said first reference signal to respective inputs of said synchronous detector for developing an intercarrier sound signal and coupling said vestigial sideband compensated IF signal and said second reference signal respectively to said first and a second inputs of said detecting means for developing a composite baseband video signal.