Local oscillator for multi-band reception having single crystal

Abstract

A local oscillator having a variable frequency oscillator and a carrier frequency oscillator for use in communication systems that transmit and/or receive signals on multiple frequency bands, one crystal reference oscillator; a converter circuit for mixing the outputs of at least the variable frequency oscillator and the carrier frequency oscillator to produce an output having a frequency corresponding to the receiving frequency and a phase-locked loop circuit including a plurality of voltage control oscillators corresponding to the number of receiving frequency bands; a mixing circuit for mixing the output of a predetermined one of the voltage control oscillators corresponding to a predetermined one of the frequency bands with the output of the converter circuit to produce an output of fixed frequency corresponding to the one frequency band; a programmable counter that divides the output of the mixing circuit in accordance with a frequency dividing ratio corresponding to the one frequency band; and a phase comparator for comparing the phase of the output signal from the programmable counter with that of the output from the one crystal reference oscillator to provide a control signal for the one voltage control oscillator whereby the one crystal reference oscillator may be employed with all of the voltage control oscillators.