熱驅動振盪器之鎖相迴路設計

Abstract

本論文使用以壓阻式感測器作為感測元件的熱驅動振盪器，設計微振盪器的量測電路，藉由振盪器的吸附平台吸附物質導致微振盪器的頻率改變，量測出振盪器的共振頻率，可以得知吸附物質的重量。 藉由熱驅動的方式促使振盪器產生振盪行為，接著透過壓阻式感測器量測其輸出電壓訊號；另外透過鎖相迴路的原理進行量測振盪器的輸入訊號與輸出訊號所產生的相位差。根據上述的方法，可進一步量測出振盪器的共振頻率。本論文利用惠斯同電橋量測壓阻式電阻的變化行為，並且針對振盪器的輸出電壓所包含的feed-through noise，提出利用乘法器與低通率波器等元件來消除輸出雜訊的調變方法。本論文所研究的振盪器元件為一三階動態系統，相較於一般常見的鎖相迴路系統通常將相位角鎖定在-90°的方式，本系統的共振頻率出現在相位角-180°，因此傳統的鎖頻方法並不適用。本論文利用相位調變的方式，將鎖相迴路中壓控振盪器相位輸出做-90°的相位延遲，進而與微振盪器產生相差相位90°的效果，來鎖定微振盪器的共振頻率。 本論文透過HSPICE軟體的0.35um 2PM4 3.3V台積電製程檔來模擬上述電路的動態變化行為，並另外利用MATLAB&SIMULINK軟體建立此整體控制系統的驗證模型架構。透過將上述兩套模擬軟體的系統參數做一整合與討論，可預期將此振盪器和驅動與感測電路實體化呈現，達到本論文機電整合的目的。

This study applied a thermal-actuated resonator by using a piezo-resistive sensor and designed the measurement circuits for micro-resonator. The resonator’s frequency will change when the plane adsorbs the material. To measure the change of resonator’s natural frequency we can know the mass of the material. The resonator was vibrated by the thermal actuator and designed a piezo- resistive sensor in the form of Wheatstone bridge circuits to measure the signal. The phase difference between the resonator input signal and output signal can be locked on -180° by the theory of Phase lock loop. According to the method, we can obtain the natural frequency of resonator. Besides, the resonator’s output signal will generate a Feed through noise. In order to reject the noise the study propose the idea by demodulating the frequency through the circuits of multiplier to reduce the noise. The resonator was a three order dynamic system, and the natural frequency located when the phase was on -180°. The phase cannot be locked by traditional Phase lock loop because the Phase lock loop usually locked the phase difference on 90°. The study used the analog RC filter to make phase delay on reference signal before passing the Phase detector. Making the phase difference between resonator output signal and reference signal on -90°. The phase and natural frequency can be locked. The circuit was simulated by Hspice 0.35um 2PM4 3.3V process, and using the MATLAB&SIMULINK to make the model of the system. Through the software, we can combine and discuss the system’s performance and data. And then the resonator and measurement circuit can be expected to present.