Reserch On Performance Of MEMS Oscillator

As the gradual growth of demand for high performance and miniaturization of devices in the electronic system, MEMS oscillator with high quality factor(Q)value, being integrated easily, resisting impact strongly and other excellent performance has become a research hotspot. The purpose of this paper is to explore the performance of MEMS oscillator, as a core component of oscillator, the MEMS resonator naturally becomes a focus of research.In this thesis, a new kind of 10 MHZ square MEMS resonators with moving electrode is designed, at the same time the method by moving electrode to reduce motional resistance resonator is studied. The initial gap between electrode and the resonant square is 2.5 μm, which is decreased to 0.5 μm through the electrostatic force after the bias voltage, 60 V, is loaded on the bias anchor. Results of harmonic simulation in ANSYS show that motional resistance of MEMS resonator mentioned is reduced to 1/626 of the initia l value. Meanwhile the design, without making the technology difficulty, can make depth to width ratio be increased from 10:1 to 50:1.Based on bulk silicon technology, machining process of general resonator is given. The layout design of both of fixed and movable electrode are completed by L- EDIT, and the two types of resonators are made. The electrical performance of the bare chip of resonators are tested by the vacuum probe station, qualitatively analyses is given on account to resonator with fixed electrodes, which has passed the test, because its frequency is offset the resonant frequency of 0.552 MHz. According to the working environmental characteristics of MEMS resonator, the condition for the encapsulation is studied, and then the metal packaging is selected. Vector network analyzer is used to test the electrical performance of encapsulated resonator. The effects of the metal packaging is evaluated by comparing results of two electrical performance test of the resonator performance.The electromechanical analogy method is adopted to transform the mechanical lumped parameter model to the corresponding electric lumped equivalent circuit model for the resonator, according to the mapping relationship between mechanical properties and electrical properties of the MEMS resonator. To reduce the complexity of the model, the difference is introduced and studied to eliminate feed-through of resonator, and the RLC series resonance equivalent circuit is obtained.O n the basis of test data, value of equivalent circuit parameters are extracted by the curve-fitting method.MEMS oscillator is designed on account of MEMS resonator with fixed electrodes, which owe more excellent performance. Main performance of MEMS oscillator circuit by the ADS simulation are as follows: the frequency of output signal is 9.44065 MHz, the output power is 14.205 d Bm. Each order even harmonic output power is less than-350 d Bm, which is almost negligible. Performance of output noise is as follow:-100.370 d Bc/Hz@0.1 Hz,-103.565 d Bc/Hz@1 Hz,-120.197 d Bc/Hz@10 Hz,-122.784 d Bc/Hz @100 Hz,-122.777 d Bc/Hz @1 k Hz.