A microcomputer-compensated crystal oscillator using a dual-mode resonator

Abstract

The system described uses microcomputer-controlled compensation wherein the correction is implemented by adding a computed offset frequency to the output of a stable oscillator. Temperature sensing is done by the use of a dual-mode oscillator system using two C-modes of an SC-cut crystal, which are combined to produce a temperature-sensitive difference frequency. System accuracies of +or-20 p.p.b. have been achieved over a temperature range of -55 degrees C to +85 degrees C.<>