Frequency modulator having two varactor diode oscillators, one weakly coupled, the other strongly coupled, to the mixing stage

Claim 1

A MODULATION CIRCUIT FOR PRODUCING HIGHLY LINEAR FREQUENCY MODULATED ELECTROMAGNETIC WAVES, COMPRISING TWO OSCILLATORS, EACH HAVING A FREQUENCY DETERMINING RESONANT CIRCUIT WITH INDUCTANCE AND CAPACITANCE, AND A PAIR OF OPPOSITELY POLED VARACTOR DIODES CONNECTED IN SERIES CIRCUIT, WITH EACH OF SAID SERIES CIRCUITS CONNECTED IN PARALLEL WITH A RESPECTIVE ONE OF THE FREQUENCY DETERMINING RESONANT CIRCUITS THEREOF, FOR VARYING THE FREQUENCY OF THE RESPECTIVE OSCILLATOR, A MODULATION SIGNAL CONNECTED TO THE COMMON CONNECTING POINTS OF THE DIODES OF EACH SERIES CIRCUIT, IN OPPOSITE SENSE TO ONE OF SAID OSCILLATORS TO THE FREQUENCY VARIATION OF THE OTHER OSCILLATOR, THE FREQUENCY OF THE RESPECTIVE OSCILLATORS BEING IN THE ABSENCE OF MODULATION SO DIFFERENT THAT THE RESULTING FREQUENCY DIFFERENCE CORRESPONDS TO A PREDETERMINED INTERMEDIATE FREQUENCY VALUE IN THE RANGE OF LOWER FREQUENCIES, MEANS FOR ESTABLISHING A FREQUENCY DISPLACEMENT FOR EACH OF SAID OSCILLATORS WHICH ARE DIFFERENT FROM ONE ANOTHER, A MIXING STAGE, A FILTER CIRCUIT, MEANS FOR CONNECTING THE OUTPUT OF EACH OSCILLATOR WITH SAID MIXING CIRCUIT, AND MEANS FOR CONNECTING THE OUTPUT OF SAID MIXING CIRCUIT WITH SAID FILTER CIRCUIT FOR OBTAINING THE OSCILLATIONS WITH THE DIFFERENCE FREQUENCY, THE BIASING OF THE VARACTOR DIODES OF THE TWO OSCILLATORS, AND THE DIFFERENT DIMENSIONING OF THE RATIO OF INDUCTANCE TO CAPACTANCE OF THE TWO FREQUENCY DETERMINING RESONANCE CIRCUITS, BEING SO DETERMINED THAT THE ABSOLUTE FREQUENCY DISPLACEMENT OF THE RESPECTIVE OSCILLATORS IS ADJUSTED TO COMPENSATE AT THE OUTPUT OF THE MIXING STAGE FOR DISTORTIONS OF EVEN ORDER.