GB664014A - Stabilization of frequency modulated oscillators - Google Patents

Abstract

664,014. Automatic frequency control systems. RADIO CORPORATION OF AMERICA. Sept. 26, 1949 [Nov. 30, 1948], No. 24678/49. Class 38 (iv). In a frequency-modulated oscillator provided with automatic frequency-control, the tendency for the A.F.C. system to reduce or annul the desired frequency modulation is counteracted by applying the modulation voltage not only to vary the oscillator frequency but also to vary the datum frequency at which the A.F.C. operates. In Fig. 3, the main oscillator 10 feeding a load 12 is arranged to beat in a rectifier 13 with a sweep oscillator 15, the beat being fed to a tuned amplifier 17 to give a pulse output whenever the beat frequency agrees with the amplifier frequency. The sweep oscillator 15 also feeds a resonance device 19, shown as a gas cell, to give a pulse output from the rectifier 20 to an amplifier 21. The pulses are compared in phase at 18 and the output voltage corrects the frequency of the klystron oscillator 10 by varying the reflector electrode voltage. The desired frequency modulation is applied through a transformer 47 and potentiometer tapping 42 to the klystron cathode; and is at the same time applied from tapping 40 to an electrode 45 in the gas cell 19 to give a corresponding variation to the resonance frequency thereof. The A.F.C. system is thus rendered ineffective to remove the frequency modulation imposed by the desired signal. In other arrangements of the invention, Fig. 1 (not shown), the A.F.C. system is similar to that described in Specification 658,198, and the frequency-modulating signal is applied to a thermionic reactance to vary the tuning of the beat amplifier 17, Fig. 2 (not shown). A further modification, Fig. 4 (not shown), employs an A.F.C. system disclosed in Specification 653,979. Reference has been directed by the Comptroller to Specification 663,065.