| 摘要 |
1,043,824. Frequency modulation; transistor oscillating circuits. SONY CORPORATION. Jan. 23, 1964, No. 3057/64. Headings H3R and H3T. Two transistor oscillators 5a, 5b of different nominal frequency each include a voltage variable capacitor 10a, 10b to which the same modulation is applied to alter the capacities and hence the frequencies in different directions; then the frequency difference of the two modulated frequencies is taken. The modulation may be a video signal and applied to the two oscillator capacitors 10a, 10b through filters 30a, 30b tuned to the unmodulated frequencies of the oscillators, and whose effect is that the impedance of the external circuit between collector and emitter of each oscillator tends to be constant during the oscillator frequency changes, and any amplitude modulation is small. The oscillators may be Colpitts type with tuning capacitors 11a 11b, or of Clapp type, and the outputs are derived from emitter circuit filters 15a, 15b with band pass centred about the mid-frequency of the frequency modulation. The difference frequency taken from mixer 31 is filtered at 38 and after amplifying at 39 may be magnetically recorded on tape.
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