Microprocessor Compensation Crystal Oscillator Design,

With the quick progressing of electronic technology, high-stability crystal oscillator is being used more and more widely. Especially, temperature compensated crystal oscillator(TCXO) is widely used in electronic equipments such as communication, navigation, radar, measure instruments etc.. As their reference frequency source, it is critical part of the above equipments, called as their "heart". Of TCXO, Microprocessor temperature compensated crystal oscillator (MTCXO) is a comparatively new-type digital compensated crystal oscillator. In this paper, first, according to vibration mode of physical picture of dual rotated Y-cut quartz crystal, we get frequency-temperature(F-T) characteristic curve of AT-cut quartz crystal resonator(at cut angle: Φ3 =0 , Φ1=35 ο6 ′) by analyzing the Christoffel equation describing flexibility sound wave in solids, which is our theory basis used to temperature compensated. Then we detailedly present the basic structures of MTCXO and work theory, parts selecting and circuit design of its every hardware circuit. Combining with F-T characteristic curve of AT-cut quartz crystal resonator, we compare some familiar numerical approximation methods and at last, we decide to use three spline interpolation to approximate. The software designs of CPU and numerical approximation cure fit are presented detailedly in the following parts and the feasibility of temperature compensated to voltage controlled crystal oscillator(VCXO) by microprocessor is proved according to experimental results got. In the end we analyze the results and, accordingly, find out some shortages in our design and give some improved ways. Compared with digital temperature compensated crystal oscillator(DTCXO), MTCXO presented in this paper has more powerful competition because of predominances such as high-stability, simple structure, small volume, micropower, low cost, working with power-up etc.. The ultimate experimental results prove that this MTCXO can work stably and its F-T stability can achieve the goal of ±5.5×10-7 with the micropower of 10mA or so during temperature range of –20～+85℃.