Miniaturization Of The Microprocessor Temperature Compensated Crystal Oscillator

With the quick development of electronic technology, high-stability crystal oscillator is being used more and more widely. Especially, temperature-compensated crystal oscillator (TCXO) is commonly used in electronic equipments such as communication, navigation, radar, measure instruments etc..Therein, microprocessor temperature compensation crystal oscillator (MTCXO) is a comparatively new-type digital compensated crystal oscillator. In this paper, a type of miniature microcomputer compensated crystal oscillator is studied. First, the frequency-temperature (F-T) characteristic of quartz crystal resonator is analyzed. Then, the frequency-temperature (F-T) characteristic curve of AT-cut quartz crystal resonator (at cut angle:Φ3 =0 ,Φ1=35 6′) is obtained based on analyzing the Christoffel equation describing flexibility sound wave in solids, which serves as the theory basis used for temperature compensated, from which the actual circuit of oscillatory circuit is designed. Moreover, the compensation principles of MTCXO are dicussed, and the basic structure and operating principles of the system are introduced systematically. Forethermore, MCU software design is presented detailedly.This powerful microprocessor ADμC814 integrates temperature sensor, ADC, DAC, and MCU, so that it lets the system make full use of the software. In the process of design, a method, which combines the software with the hardware, is used to replace a large number of hardware circuits. Hence, it is beneficial for greatly reducing the size and manufacturing costs of crystal oscillators.Finally, based on the analysis of the experiment results, an improved scheme is put forward, that is, the application of the external temperature sensor DS18B20, which avoids the error caused by low precision of the internal sensor and interference and improves system output frequency to some degree.