Research Of MEMS Oscillator Technology And Its Application

With the increasing speed of miniaturization and integration of electronic system,the study of miniaturization, integratable high-performance oscillator has become a hot spot. The MEMS resonator with its high quality factor value, being integrated, good impact resistance and other excellent performance makes it possible to develop a compact, integrated high-performance oscillator.In this thesis, low dynamic impedance and high quality factor MEMS resonator are studied as the dynamic impedance and quality factor have a significant impact on the design and performance of MEMS oscillators. Besides considering the processing technology and the difficulty of the package, the theoretical analysis of the capactive MEMS resonator and the piezoelectric MEMS resonator is carried out. Since the piezoelectric coupling coefficient is much larger than the capacitive coupling coefficient,and the dynamic impedance is inversely proportional to the square of the coupling coefficient, the dynamic impedance of the piezoelectric MEMS resonator is generally lower than that of the capacitive MEMS resonator. Gas damping is generally the main factor limiting the value of capacitive MEMS resonators. Therefore, in order to obtain high quality factor, the capacitive MEMS resonator needs vacuum packaging, otherwise,it can not work. But the gas damping has little effect on the piezoelectric MEMS resonator, and for the non-vacuum package the resonator can obtain high quality factor.For length-extensional bulk acoustic mode resonator, the dynamic impedance is proportional to the thickness of the resonator and is inversely proportional to the width and quality factor of resonator. Based on this, the simulation design is carried out. In addition, the ring contour mode resonator is analyzed theoretically and verified by simulation. The processing flow of the MEMS resonator is given based on the piezoelectric machining technology. The layout of the resonator is completed according to the design dimension. And these two different shapes and modal resonators are processed according to the layout. Finally, a length-extensional bulk acoustic mode resonator which resonant frequency is 31.23 MHz, insertion loss is 21dB, quality factor is 1951 and a ring contour mode resonator which resonant frequency is 186.22 MHz,insertion loss is 15.39dB, quality factor is 5207 are designed.The MEMS resonator is tested and the test data is analyzed. The equivalent circuit model of length-extensional bulk acoustic mode resonator is established, and the MEMS oscillator is designed based on this. The oscillation frequency of the MEMS oscillator that is finally tested is 31.037 MHz, and its phase noise is-95.71dBc/Hz@1kHz.The frequency synthesizing technology is briefly introduced. The MEMS oscillator model is established by ADIsimPLL, and the model is used to simulate the phase locked loop in ADIsimPll. According to the simulation results, the application of the MEMS oscillator in frequency source is analyzed and explained.