| 摘要 |
PURPOSE:To make it possible to adopt only merit of the conventional voltage synthesizer system and the PLL frequency synthesizer system, by interposing the second mixer between the first mixer for intermediate frequency conversion and a PLL and supplying the output of a frequency variable oscillator, which has the oscillation frequency controlled by the AFC voltage from the IF stage, to this mixer. CONSTITUTION:The second mixer 10 and frequency variable oscillator (VFO) 11 are provided further. Mixer 10 is interposed between the first mixer 3 and the PLL, and mixes output fPLL of voltage control oscillator (VCO) 5 and output fAFC of VFO11. Oscillation frequency fAFC of VFO11 is controlled by AFC output (voltage) VAFC of IF stage 4, and the fundamental frequency is controlled by the AFC voltage. As a result, degradation of tone quality and so on is not generated and the indicated frequency based on fPLL agrees with receiving frequency fANT in case of tuning slippage. Meanwhile, when the tuning frequency of IF stage 4 is shifted, AFC output VAFC appears, and VFO11 changes the frequency so that VAFC=0 may be true. |
