| 摘要 |
PURPOSE:To attain stable acquistion of synchronism of a VCO within the frequency range, when the hold range of a PLL is narrower than the variable frequency range of the VCO, by detecting the stop of oscillation of the 2nd sweep oscillator when the loop is locked and holding the output voltage of the 1st sweep oscillator. CONSTITUTION:An output of the VCO1 is inputted to a phase comparator 2, the phase of the output is compared with that of a reference oscillator 3, and the output is applied to a loop amplifier 5 inputting the output of a sweep oscillator 6. The output of the amplifier 5 is applied to an addition circuit 9 directly and via a sweep oscillator 7, and the VCO1 is controlled with the output of the circuit 9. The stop of oscillation of the sweep oscillator 7 is detected at a control circuit 8 and the oscillating output of the oscillator 6 is held with the control of the control circuit 8. When the holding range of the PLL is narrower than the variable frequency range of the VCO1, the stable acquistion of synchronism is attained within the variable frequency range of the VCO1. |
