| 摘要 |
PURPOSE:To prevent the influence of the junction capacity of an oscillating transistor upon the modulation characteristics, by providing a modulation signal attenuating circuit on a signal line connecting a resonance circuit having a varactor diode and the base of the oscillating transistor. CONSTITUTION:A trap circuit 22 as a modulation signal attenuating circuit is provided on the signal line connecting a resonance circuit 21, which consists of an inductance 4 and a varactor diode 5, and the base of an oscillating transistor (TR) 2, and an LPF23 is provided between a modulation signal source 13 and the circuit 21. The circuit 22 constitutes a band stop filter. The modulation signal from the signal source 13 is pulled up by a DC power source 14 and is applied to the diode 5 and changes the capacity to perform the frequency modulating operation, and a signal to be modulated is outputted from a terminal 18. The circuit 22 eliminates mainly high-band components of the modulation signal applied to the base of the TR2. Thus, the influence of the junction capacity, which exists between the base and the collector of the TR2, upon the frequency modulation is reduced very much. |
