Improvements in or relating to the automatic frequency control of electric oscillation generators

摘要

775,573. Automatic frequency control systems. GENERAL ELECTRIC CO., Ltd. April 6, 1955 [April 9, 1954], No. 10552/54. Class 38 (4). The mean frequency of a frequency or phasemodulated oscillator 1 is retroactively stabilized by alternately applying its oscillations and those of a stable constant frequency reference oscillator 4 to a frequency discriminator 9 (of crossover frequency equal to the mean frequency of the oscillator 1 and reference oscillator 4) through a gate 7 controlled by a switching frequency 19, e.g. mains frequency of 50 c/s., converted to a rectangular waveform, and a limiter comprising an amplifier 12 with fast-acting automatic gain control loop 8. The discriminator output may then be amplified, and passed through a low-pass filter 16 (of cut-off frequency, e.g., 75 c/s.) to a sense discriminator 18 with input also obtained from the switching frequency 19 and output in magnitude and polarity stabilizing the mean frequency of the oscillator 1.