| 摘要 |
PURPOSE:To apply sufficiently modulation even to the low frequency component of an input signal by using an input signal and a signal component passing the input signal through an LPF, and applying again modulation to a voltage controlled oscillator. CONSTITUTION:The phase of an output of a variable frequency divider 2 selecting an output frequency of the voltage controlled oscillator 1 is compared 3 with a reference frequency fO in phase and the compared output is outputted to a synthesis circuit 8. The circuit 8 synthesizes the compared output with a signal integrating a modulating input signal vin at an integration circuit 7, and the synthesized output is inputted to a synthesis circuit 5 via an LPF4. The circuit 5 synthesizes the signal vin with an output of the LPF4, controls the oscillator 1 so as to apply the FM modulation by the PLL system. Since the signal vin and a low frequency signal component obtained by passing the signal vin through the LPF4 apply modulation to the oscillator 1, the modulating characteristic is not deteriorated to the low frequency component of the signal vin. |
