摘要 |
PURPOSE:To make the operation of a sweep circuit stable by comparing the phase of an input reference signal with the phase of an output signal of a voltage controlled oscillator at a sampling phase comparator, inputting the resulting signal to a loop filter and inputting the output of the loop filter to a sweep oscillator and a buffer amplifier. CONSTITUTION:The phase of an input reference signal fed to an input terminal 2 is compared with a phase of an output of a voltage controlled oscillator 7 at a sampling phase comparator 1, and a loop filter 3 eliminates noise and a high frequency component from an output of the sampling phase comparator 1. Even when an input impedance of an in-phase detector 6 is low, since the output impedance of a buffer amplifier is low, the detector 6 can supply a current enough to charge a capacitor. Moreover, since the input impedance of the buffer amplifier 5 is high, the output voltage of the loop filter 3 is not affected by the buffer amplifier 5. |