| 摘要 |
PROBLEM TO BE SOLVED: To improve the C/N of the receiver and to enhance the performance by improving a high frequency component and noise eliminating performance of a loop filter being a component of a phase locked loop(PLL) of the receiver. SOLUTION: The output of a voltage controlled oscillator 1 is given to a multiplier circuit 3 via a buffer circuit, from which a local output is obtained. The oscillated frequency signal extracted from the multiplier circuit 3 is given to program frequency divider 4, where the signal is frequency-divided by a frequency division ratio N. A reference frequency signal is generated by a crystal 7 and a reference frequency divider 5 and a phase detector 6 detects a phase difference between an output frequency Fs of the programmable frequency divider 5 and the reference frequency divider 5 and provides an output. The output signal is integrated by a low pass filter 8 of a loop filter 10 into an error voltage and a variable notch filter 9 eliminates a high frequency component and noise and the resulting signal is used to control the voltage controlled oscillator 1. The variable notch filter 9 is made up of a power supply use variable notch filter and a reference frequency variable notch filter. |
