| 摘要 |
807,513. Automatic frequency and phase control systems. RADIO CORPORATION OF AMERICA. Aug. 10, 1955 [Sept. 1, 1954], No. 23102/55. Class 38 (4). [Also in Group XL (c)] A self-running single transistor oscillator 44 is phase-locked with an incoming reference wave, e.g. the subcarrier reference burst 36 of a colour television signal, applied to its base or emitter electrode, by a D.C. voltage, corresponding in magnitude and sign to any phase difference, developed in a time constant R-C circuit 60, 66 in series with the collector electrode supply voltage, this derived voltage acting as a control voltage varying the collector-base output capacitance of the transistor until frequency and phase synchronism is restored. As shown, a tapping 72 of the tank circuit 58 is regeneratively coupled to the emitter through a capacitor 70 and piezo-electric crystal 68 acting as a filter. In a modification the base is earthed and the reference burst 36 transformer-coupled to the emitter input circuit. Also variable resistors shunt the R-C circuit 60, 66 and emitter input circuit to enable manual adjustment of the natural frequency of the oscillator. Specification 760,749 is referred to. |
