Local oscillator apparatus for low-noise generation of arbitrary frequencies

摘要

A method and apparatus are hereby presented for the purpose of supplying local oscillator frequencies used for upconversion and downconversion of electronic signals for transmitters or receivers. The apparatus contains a voltage controlled oscillator for generating the signal used for upconversion or downconversion, a reference signal, a second oscillator or source locked to the reference signal which is used in a heterodyne loop for the purpose of enabling any arbitrary frequency to be generated, a sampling phase detector which is part of the heterodyne loop, and dividers for dividing the reference signal as well as the heterodyne output of the sampling phase detector. The purpose of the heterodyne loop is twofold. By reducing the frequency by means of heterodyne action the divider ratio can be kept small, thus reducing the phase noise. Also, the heterodyne technique permits the synthesis of any arbitrary frequency, through the choice of the appropriate heterodyne frequency.