Suppressed-carrier amplitude-modulation detector for use in an fm stereo multiplex receiver

Claim 1

A RECEIVER FOR USING A STEREOPHONIC PROGRAM COMPRISING A CARRIER FREQUENCY-MODULATED IN ACCORDANCE WITH THE SUM OF TWO AUDIO SIGNALS AND ALSO IN ACCORDANCE WITH A SUBCARRIER SIGNAL WHICH HAS BEEN SUPPRESSED-CARRIER AMPLITUDE-MODULATED WITH THE DIFFERENCE OF SAID TWO AUDIO SIGNALS, SAID RECEIVER COMPRISING: A FREQUENCY-MODULATION DETECTOR RESPONSIVE TO SAID CARRIER FOR DERIVING A COMPOSITE SIGNAL REPRESENTING THE MODULATION OF SAID CARRIER; A SUPPRESSED-CARRIER AMPLITUDE-MODULATION DETECTOR INCLUDING A SINGLE TRANSISTOR HAVING BASE, EMITTER AND COLLECTOR ELECTRODES, HAVING A BACKWARD CURRENT GAIN, AND HAVING A FORWARD CURRENT GAIN SUBSTANTIALLY GREATER THAN SAID BACKWARD CURRENT GAIN; SAID AMPLITUDE-MODULATION DETECTOR FURTHER INCLUDING A PAIR OF LOAD CIRCUITS COUPLED TO SAID EMITTER AND COLLECTOR ELECTRODES, RESPECTIVELY; A SIGNAL SOURCE, HAVING A SOURCE IMPEDANCE LESS THAN THE IMPEDANCE OF SAID LOAD CIRCUITS, FOR APPLYING AT LEAST THE SUPPRESSED-CARRIER AMPLITUDE-MODULATED COMPONENT OF SAID COMPOSITE SIGNAL TO SAID BASE ELECTRODE OF SAID TRANSISTOR; MEANS FOR APPLYING IN PUSH-PULL RELATION TO SAID EMITTE AND COLLECTOR ELECTRODES OF SAID TRANSISTOR A DEMODULATION SIGNAL CORRESPONDING TO THE CARRIER FREQUENCY OF SAID SUBCARRIER SIGNAL OF SAID COMPOSITE SIGNAL TO DEVELOP IN SAID LOAD CIRCUITS A DETECTED SIGNAL REPRESENTING THE DIFFERENCE OF SAID TWO AUDIO SIGNALS; AND MEANS FOR MATRIXING AT LEAST THAT PORTION OF SAID COMPOSITE SIGNAL WHICH REPRESENTS THE SUM OF SAID TWO AUDIO SIGNALS WITH SAID DETECTED SIGNAL REPRESENTING THE DIFFERENCE OF SAID TWO AUDIO SIGNALS TO DERIVE A PARTICULAR ONE OF SAID AUDIO SIGNALS SEPARATED FROM THE OTHER OF SAID AUDIO SIGNALS.