Precision Self Sensing and Compensation Applications of Crystal Oscillators

The root cause of frequency aging drift and temperature variation in crystal oscillators is the variation of resonant parameters of resonators. Changing the resonance parameters can cause a change in the phase between the two ends of the resonator, or between one end of the resonator and the output end of the oscillator. By detecting the phase shift between the two ends of the resonator, the changes in resonance parameters can be reflected. Therefore, the phase shift at both ends of the crystal resonator reflects the sensing characteristics of the oscillation frequency, and indicate its error, which can reflect the frequency changes caused by any reason of the crystal oscillator. We have solved the high-precision linear phase measurement technology for digital methods of detecting resonator phase shift. Through preliminary experiments, the relationship between the resonator phase shift of the crystal oscillator and the oscillator frequency can be formed by processing such as median filtering of noise. When their changing patterns are the same the relationship will be linear. A large number of experiments have shown that linear situations are common with long-term stable operation of oscillators and special temperature characteristics of crystals respectively. Based on self- sensing, the accuracy of the crystal oscillator will greatly exceed that of traditional frequency stabilization methods. The stability of the phase between the two ends of the crystal resonator itself relative to the synchronous change of the oscillator frequency is the actual accuracy holding ability. This self-sensing method will have a profound impact on the advancement of frequency source technology.