| 摘要 |
PURPOSE:To improve an S/N ratio and to reduced distortions with simple constitution by applying a control voltage to a voltage-controlled oscillator via a distortion compensating circuit, composed of a diode and a resistance, in a circuit which uses a PLL. CONSTITUTION:In an FM modulating and an FM demodulating circuit, distortion compensating circuits CPS1 and CPS2 are connected between amplifiers AMP1 and AMP2, and voltage-controlled oscillators VCO1 and VCO2. The CPS1 and CPS2 are each composed of a parallel circuit of a diode and a resistance, and characteristics inverse of voltage frequency characteristics of the VCO1 and VCO2 are obtained by adjusting resistance values of them. Consequently, distortions due to the nonlinearity of the VCO1 and VCO2 are compensated and an S/N ratio is therefore improved by making the sensitivity of the VCO1 and VCO2 relatively small. In addition, distortions are reduced. |
