实现AT切石英晶体振荡器微处理器温度补偿的新方法

本文介绍实现AT切石英晶体振荡器微处理器温度补偿的新方法——双频温度自测法.AT切石英谐振器各泛音次数的频率温度曲线不同,利用基频与3次泛音除一阶温度系数不同外其他各阶温度系数相等的特性,基频的3倍频与3次泛音频率的差频输出与温度近似成线性关系.同时激励并测量基频和3次泛音频率,经过微处理器计算差频实现谐振器温度自测并进行晶体振荡器的微处理器温度补偿.与使用分立温度传感器相比,消除了测温元件与石英谐振器温度时间常数不同以及温度场梯度造成的测温误差,提高了测温和补偿精度.

A Novel Implementation Method to Microprocessor Compensated Crystal Oscillator

This paper describes a novel method to realize microprocessor compensated crystal oscillator (MCXO) by using the dual-mode excited AT-cut quartz crystal resonator (QXR).According to the harmonic effect,normalized beat frequency of the 3rd overtone frequency and 3 times of the fundamental frequency is almost linearly dependent on the changes of ambient temperature.By stimulating the fundamental and the 3rd overtone frequencies output simultaneously,the changes of ambient temperature was measured by the beat frequency and the temperature compensation was accomplished by the utilization of the dependence of the temperature on the beat frequency and the method of pulses deletion.This temperature measurement technique can eliminate the thermal lag due to the difference in thermal time constants of the QXR and the thermistor,and can overcome the limitation of temperature field gradient.The implementation of the means in MCXO is described.The dual-mode oscillating circuit and its block diagram are given and the practical experimental data are discussed.