| 摘要 |
<P>PROBLEM TO BE SOLVED: To solve the problem wherein a signal of an accurate frequency cannot be supplied when a shift voltage generation circuit is prepared in order to match a variance voltage range of a loop filter with a permission input range of a voltage controlled oscillator, since power supply variation from a reference voltage power supply or ground is superimposed on a control input voltage of the voltage controlled oscillator. <P>SOLUTION: The shift voltage generation circuit of the voltage controlled oscillator produces a summing voltage signal and an intermediate reference voltage signal from a same reference voltage power supply to make a phase of voltage variation waveform of each signal equal, and inputs each signal into differential input of an operational amplifier to eliminate voltage variation. In addition, a low-pass filter is provided between the reference voltage power supply and a summing voltage signal or an intermediate reference voltage signal output to suppress the voltage variation. Thereby, control input voltage without voltage variation can be input into the voltage controlled oscillator, and an output signal of an accurate frequency can be supplied. <P>COPYRIGHT: (C)2010,JPO&INPIT |
