Frequency converter for outputting a stable frequency by feedback via a phase locked loop

摘要

A frequency converter capable of providing a highly stable frequency by frequency feedback using a phase locked loop circuit. The frequency converter includes a local oscillator; a frequency converter for mixing an output of the local oscillator and a feedback frequency therefrom to generate a mixed frequency; a first filter for filtering the mixed frequency; a phase comparator for generating a voltage signal corresponding to a phase difference in between an input frequency to the frequency convertor and the output frequency of the first filter; a second filter for converting the voltage signal of the phase comparator to a constant polarity voltage and eliminating any noise component of the converted voltage signal; and a voltage controlled oscillator receiving the output of the second filter as a control voltage so as to provide a stable output frequency by generating the feedback frequency responsive to the control voltage.