| 摘要 |
PURPOSE:To obtain a fixed frequency shift even for a large change ratio of the oscillation frequency, by setting the capacity ratio of two oscillation frequency varying varactor diodes D, which are connected in parallel, to a prescribed value. CONSTITUTION:The resonance frequency is determined by the resultant capacity consisting of frequency modulating variable capacity D34, DC cutting-off capacitors C30 and C31, and frequency varying variable capacities D32 and D33 and the inductance of oscillation coil 36. The oscillation frequency is changed by changing the voltage of frequency setting power source 38 applied to D32 and D33. The modulation signal applied to terminal 24 is applied to D34 through C25 and high frequency stopping choke 29, and frequency modulation is performed by changing the resonance frequency by the modulation signal. The capacity ratio of D32 and D33 is varied while keeping frequency shift constant, for example, the capacity of D32 is set to a value approximately twice as large as the capacity of D33, thereby obtaining a fixed frequency shift even for a large change ratio of the oscillation frequency. |
