| 摘要 |
1,147,362. Automatic frequency control. SPACE-GENERAL CORP. 27 Sept., 1966 [27 Sept., 1965], No. 43036/66. Heading H3A. In a superheterodyne radio receiver the local oscillator 13 comprises a voltage controlled oscillator 43, a crystal controlled oscillator 50, a mixer 52 for combining the outputs from the two oscillators, a phase detector 54 for comparing the phase of the combined signal with a reference signal from a source 51, and means supplying the phase detector output to control the frequency of the oscillator 43. The controlled frequency may be varied by changing the crystals in the oscillator 50. Switch 44 provides means whereby the frequency of the reference source may be adjusted in dependence on the phase of the I.F. output signal, by comparing the I.F. output and the reference signal in a further phase detector, Fig. 1a (not shown). Switch 56 provides an alternative mode of operation in which an AFC signal is obtained from the I.F. output in a conventional manner. |
