A New Type Of Small-size Microcomputer Compensated Crystal Oscillator

As the development of electronic technology, high-stability crystal oscillator isbeing used more and more widely. Especially, the temperature compensated crystaloscillator (TCXO) which works immediately after starting up, is used in electronicequipments such as communication, navigation, radar, measure instruments etc.. It is the"heart" of these equipments, because it works as the reference frequency source and thecritical part of them.Microprocessor temperature compensated crystal oscillator (MTCXO) is anew-type digital compensated crystal oscillator. According to vibration mode ofphysical 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°10′) by analyzing the Christoffel equation which describesflexibility sound wave in solids, which is the theory basis of temperature compensation.Then we detailedly present the basic structures of MTCXO, the working theory, chipselection and circuit design.After that, we introduce the lower-power-consumptiondesign form hardware and software. Combining with F-T characteristic curve of AT-cutquartz crystal resonator, we decide to use the least square method to realize the functionapproximation. The software designs of CPU and numerical approximation cure fit arepresented detailedly in the following parts. This method of temperature compensation isproved feasibly according to the experimental results.At last we analyze the results and find out some shortages in our design and givesome improved ways. Compared with digital temperature compensated crystaloscillator(DTCXO), MTCXO presented in this paper has many predominances, such ashigh-stability, simple structure, small in size, lower power consumption, etc.. Theultimate experimental results prove that its stability can arrive at±4.7×10^-7 during thetemperature range of -40～+85℃, while power consumption is 6.63mA (@3.3V), andits size is 19×12×10mm³.