Stabilized phase-sensitive servo loop demodulators

Claim 1

IN A PHASE SENSITIVE SERVO LOOP DEMODULATOR, INCLUDING A PHASE SENSITIVE DETECTOR HAVING AN INPUT ARRANGED TO BE IMPRESSED WITH FREQUENCY MODULATED CARRIER TO BE DEMODULATED, AND HAVING AN OUTPUT, AND A FREQUENCY MODULATED VARIABLE-FREQUENCY OSCILLATOR HAVING A MODULATION INPUT AND HAVING AN OUTPUT CONNECTED TO SAID PHASE SENSITIVE DETECTOR FOR COMBINING THEREIN WITH THE MODULATED CARRIER, MODULATOR CIRCUIT MEANS FOR APPLYING OUTPUT FROM SAID PHASE SENSITIVE DETECTOR AS A REACTANCE MODULATION SIGNAL TO THE INPUT OF SAID VARIABLE-FREQUENCY OSCILLATOR TO VARY THE FREQUENCY OF THE LATTER AND FORM A SERVO LOOP WHEREIN OSCILLATOR FREQUENCY TRACKS THE INCOMING CARRIER FREQUENCY, SAID MODULATOR CIRCUIT MEANS COMPRISING OPPOSING INPUT TERMINALS ACROSS WHICH IS IMPRESSED OUTPUT SIGNAL FROM SAID DETECTOR, A PAIR OF VOLTAGE-CONTROLLED VARIABLE REACTANCE ELEMENTS EACH HAVING ANODE AND CATHODE TERMINALS, THE ANODE TERMINAL OF ONE SUCH ELEMENT AND THE CATHODE TERMINAL OF THE OTHER SUCH ELEMENT BEING CONNECTED TO ONE SIDE OF THE OSCILLATOR INPUT SEPARATE CONNECTIONS FROM THE REMAINING TERMINALS OF SAID ELEMENTS TO THE OPPOSITE SIDE OF THE OSCILLATOR INPUT, SIMILAR CONSTANT-REACTANCE ELEMENTS INTERPOSED IN THE RESPECTIVE CONNECTIONS BETWEEN THE REMAINING TERMINALS OF SAID VARIABLE REACTANCE ELEMENTS AND SAID REMAINING SIDE OF THE OSCILLATOR MODULATION INPUT, AND SEPARATE CIRCUIT MEANS CONNECTED BETWEEN THE MODULATOR INPUT TERMINALS AND SAID REMAINING TERMINALS OF THE VARIABLE REACTANCE ELEMENTS, RESPECTIVELY, SAID SEPARATE CIRCUIT MEANS INCLUDING MEANS APPLYING ACROSS EACH SUCH VARIABLE REACTANCE ELEMENT A VARIABLE VOLTAGE COMPONENT SUBSTANTIALLY PROPORTIONAL TO OUTPUT FROM SAID DETECTOR, THE MODULATOR CIRCUIT MEANS APPEARING ELECTRICALLY SUBSTANTIALLY SYMMETRICAL BOTH AT ITS INPUT AND OUTPUT.