| 摘要 |
PURPOSE:To keep the control characteristic of a phase locked loop by providing a DC amplifier amplifying an output signal of a loop filter being a component of the phase locked loop with an amplification factor set externally and varying the amplification factor. CONSTITUTION:A DC amplifier 6 is interposed on the output of a loop filter 4. Through the constitution above, after a high frequency output signal of a voltage controlled oscillator 1 is frequency-divided by a frequency divider 2, the signal is phase-compared with an output signal of a reference frequency oscillator 5 by the phase comparator 3. A phase error detected therein is converted into a DC voltage by the loop filter 4, amplified at the DC amplifier 6 and fed back to the voltage controlled oscillator 1 as a control voltage. The amplification factor of the DC amplifier 6 is varied externally, then it is prevented that the conversion gain of the voltage controlled oscillator 1 is decreased as the frequency is higher and the control characteristic of the phase locked loop is kept constant. |
