Stereophonic decoder
AssigneeKabushiki Kaisha Toshiba
InventorsAtsusi Ogawa, Tsuneyuki Murayama
Life of this patent
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Abstract
A compatible quadrature type AM sterophobic decoder including an enveolpe detector for providing a current output signal and a combination of a VCA and a synchronous detector for providing a current output signal. The combination of the VCA and the synchronous detector is controlled by a feedback signal from an adder which adds the current output signal of the envelope detector and the inverting current output signal of the conbination of the VCA and the synchronous detector.
Claims7
A compatible quadrature AM stereophonic decoder, comprising:
- an envelope detector for detecting an IF signal of a compatible AM signal and providing a compatible monophonic (1+L+R) signal to a matrix circuit;
- and
- a combination of a VCA circuit and a synchronous detector for detecting the IF signal and providing a quadrature monophonic (L-R) signal to the matrix circuit for separating and demodulating left and right channel signals;
- wherein:
- the envelope detector is comprised of a current output type detector and the combination of the VCA circuit and the synchronous detector is also comprised so as to provide current output signals;
- and
- the VCA circuit is controlled by a feedback signal which comes from an adder for adding the current output of the envelope detector and the current output of the combination of the VCA circuit and another synchronous detector in order to maintain a same current level between the signals to the matrix circuit.
A compatible quadrature type AM stereophonic decoder for processing a received AM stereophonic signal and providing a pair of L and R signals through a matrix circuit, comprising:
- an envelope detector;
- an amplifying stage for providing an IF signal of the received AM stereophonic signal to the envelope detector and a VCA circuit;
- the envelope detector for supplying a compatible monophonic (1+L+R) current signal which corresponding to a modulated component of the IF signal;
- the VCA circuit for supplying a voltage control amplifying signal in response to an input of the IF signal;
- an in-phase synchronous detector for detecting a carrier signal of the IF signal with a first reference signal which is in-phase to the carrier signal of IF signal and supplying an inverted -(1+L+R) current signal;
- a quadrature synchronous detector for detecting a carrier signal of the IF signal with a second reference signal which is quadrature to the carrier signal of IF signal and supplying a quadrature (L-R) current signal;
- an adder for adding the output current signal of the envelope detector and the output current signal of the in-phase synchronous detector;
- and
- an integrator for supplying a feedback voltage signal of the output current from the adder to the VCA.
A compatible quadrature type AM stereophonic decoder for processing a received AM stereophonic signal and providing a pair of L and R signals through a matrix circuit, comprising:
- an amplifying stage for providing an IF signal of the received AM stereophonic signal;
- an envelope detector for supplying a compatible monophonic (1+L+R) current signal which corresponding to a modulated component of the IF signal;
- a VCA circuit for supplying a voltage control amplifying signal in response to an input of the IF signal;
- an in-phase synchronous detector for detecting a carrier signal of the IF signal with a first reference signal which is in-phase to the carrier signal of IF signal;
- a first VCA circuit for receiving an output of the in-phase synchronous detector and supplying an inverted -(1+L+R) current signal;
- a quadrature synchronous detector for detecting a carrier signal of the IF signal with a second reference signal which is quadrature to the carrier signal of IF signal;
- a second VCA circuit for receiving an output of the quadrature synchronous detector and supplying a quadrature (L-R) current signal;
- an adder for adding the output current signal of the envelope detector and the output current signal of the first VCA circuit;
- and
- an integrator for supplying a feedback voltage signal of the output current from the adder to the first and second VCA circuits.
Dependencies are inferred from the claim text.