Frequency modulation communication system having automatic frequency derivation control in response to received thermal noise

Claim 1

IN A FREQUENCY-MODULATION SYSTEM INCLUDING A TRANSMITTER AND A RECEIVER, SAID TRANSMITTER HAVING FREQUENCYMODULATION MEANS FOR PRODUCING A FREQUENCY-MODULATED INTELLIGENCE-BEARING SIGNAL AND MEANS FOR TRANSMITTING SAID SIGNAL, THE PROVISION OF A MONITORING ARRANGEMENT FOR AT ALL TIMES MAXIMIZING THE SIGNAL-TO-NOISE RATIO AT THE RECEIVER COMPRISING: A HIGH-PASS THERMAL NOISE FILTER CONNECED TO THE RECEIVER FOR SELECTIVELY DERIVING A SIGNAL CORRESPONDING TO A THERMAL NOISE COMPONENT ACCOMPANYING THE RECEIVED INTELLIGENCE-BEARING SIGNAL AS AN INDICATION OF THE STRENGTH OF SAID LATTER; INTEGRATOR MEANS CONNECTED TO THE OUTPUT OF THE FILTER MEANS FOR DERIVING FROM SAID THERMAL NOISE SIGNAL A MONITORING SIGNAL CORRESPONDING TO AVERAGED THERMAL NOISE; VARIABLE MEANS CONNECTED TO SAID FREQUENCY-MODULATION MEANS FOR MODIFYING THE FREQUENCY-DEVIATION OF SAID INTELLIGENCE-BEARING SIGNAL; AND MEANS CONNECTED FOR VARYING SAID VARIABLE MEANS IN ACCORDANCE WITH VARIATIONS IN SAID MONITORING SIGNAL WHEREBY TO MAINTAIN SAID FREQUENCY-DEVIATION SUBSTANTIALLY AT ITS OPTIMAL VALUE CORRESPONDING TO MINIMUM NOISE-TO-SIGNAL RADIO AT THE RECEIVER.