Direct indicating frequency determining circuit employing peak detecting combined delayed and undelayed signals of unknown frequency

Claim 1

A FREQUENCY DISCRIMINATOR RESPONSIVE TO A SINUSOIDALLY VARYING INCIDENT SIGNAL HAVING AN UNKNOWN FREQUENCY F+$F, WHERE F IS A PREDETERMINED FREQUENCY AND $F IS A DIFFERENCE IN FREQUENCY FROM THE PREDETERMINED FREQUENCY, FOR PRODUCING AN OUTPUT VOLTAGE PROPORTIONAL TO AND INDICATING THE UNKNOWN FREQUENCY F+$F OF THE SINUSOIDAL INCIDENT SIGNAL, SAID DISCRIMINATOR COMPRISING A FILTER HAVING AN INPUT AND AN OUTPUT AND HAVING UPPER AND LOWER FREQUENCY LIMITS DEFINING THE BAND OF SIGNAL FREQUENCIES PASSED BY SAID FILTER, ONE OF SAID FREQUENCY LIMITS BEING APPROXIMATELY EQUAL TO MF/2, WHERE M IS AN ODD INTEGER, THE OTHER ONE OF SAID FREQUENCY LIMITS BEING APPROXIMATELY EQUAL TO NF/2, WHERE N IS AN EVEN INTEGER ADJACENT THE INTEGER M, MEANS FOR APPLYING THE INCIDENT SIGNAL OF UNKNOWN FREQUENCY TO THE INPUT OF SAID FILTER, A LIMITER HAVING AN INPUT CONNECTED TO THE OUTPUT OF SAID FILTER AND HAVING AN OUTPUT, A DELAY LINE HAVING AN INPUT CONNECTED TO THE OUTPUT OF SAID LIMITER, HAVING AN OUTPUT AND CHARACTERIZED BY A TIME DELAY EQUAL TO THE RECIPROCAL OF THE PREDETERMINED FREQUENCY, AN ATTENUATOR HAVING AN INPUT CONNECTED TO SAID LIMITER OUTPUT AND HAVING AN OUTPUT, SAID ATTENUATOR AND SAID DELAY LINE HAVING EQUAL SIGNAL ATTENUATION CHARACTERISTICS, A DIFFERENCE AMPLIFIER HAVING A FIRST INPUT CONNECTED TO THE OUTPUT OF SAID DELAY LINE AND A SECOND INPUT CONNECTED TO THE OUTPUT OF SAID ATTENUATOR AND HAVING AN OUTPUT, SAID DIFFERENCE AMPLIFIER PRODUCING AN OUTPUT PROPORTIONAL TO THE DIFFERENCE BETWEEN THE DELAYED SIGNAL AND THE ATTENUATED SIGNAL, AND SATISFYING THE RELATIONSHIP