| 摘要 |
PURPOSE:To obtain an oscillating output frequency stable for a long time even when intermitted Phase Locked Loop is implemented by providing a specific voltage generating circuit and a specific control voltage switching circuit respectively on this synthesizer. CONSTITUTION:The synthesizer is provided with a voltage generating circuit 12 generating a control voltage equal to or close to an output voltage of a loop filter 5 at a phase-locked state when the phase-locked loop reaches the phase-locked state and with a control voltage changeover circuit. Then the control voltage switching circuit selects the output voltage of the loop filter 5 while the phase-locked loop reaches the phase-locked state and gives the selected voltage to a voltage controlled oscillator 10. Moreover, a control voltage outputted from the voltage generating circuit 12 is selected while the phase- locked loop reaches the phase-locked state and fed to the voltage controlled oscillator 10. Thus, even in the case of intermittent phase-locked loop state, the oscillating output frequency stable for a long time is obtained. |
