表面聲波元件之設計及其在寬頻振盪器之應用

Abstract

本論文利用Mason等效電路模型來模擬壓電材料中表面聲波的特性，並成功地製作出以ST-Quartz為壓電基材的單埠表面聲波諧振器，其工作頻率在433.92MHz，可應用於一般遠距遙控器或無線通訊系統中所需的共振槽路（Resonance Tank）；而其量測結果與我們模擬所預測的響應，有相當不錯的吻合度，可謂是成功地模擬出表面聲波的電氣特性。再者，我們依所研製的表面聲波諧振器，有效地粹取出其等效電路模型中的各個參數，並提出從表面聲波諧振器由初始製程到元件封裝完成各步驟中其頻率響應所造成的影響，以提供設計者於設計之初即能將封裝過程所將造成之影響一併考慮進來，以期能準確地設計所需頻段的表面聲波諧振器，更能因此提高製程上的良率，以獲致大量生產的效果。 最後，我們利用阻抗轉換器（Impedance Inverter）克服表面聲波諧振器天生窄頻的限制，成功地設計出一寬頻壓控表面聲波振盪器（Voltage Control SAW Oscillator；VCSO），其可調頻寬達1.23MHz，在低調變電壓2~8V的區域內具有極佳的線性度，且其調變斜率高達190KHz/V，而其輸出功率為10dBm，在偏離載波10kHz處具有-120dBc/Hz的低相位雜訊；以作為應用於現今無線通訊網路中高性能的本地振盪器，或是應用於鎖相迴路與頻率合成器中的VCO（Voltage Control Oscillator）。

One-Port Surface Acoustic Wave Resonator（SAWR）with operation frequency in 433.92MHz as remote control security, automobile keyless entry or resonator tank used in wireless communication system is fabricated using ST-Quartz substrate. The SAWR is designed by using Mason equivalent circuit model. And it has good agreement between our simulation and measurement. Moreover, SAWR motional and package parasitic parameter is also extracted in this paper. Furthermore, the frequency shift due to bondwire and package’s EMC effect from fabricating to completely packaging is presented using on-wafer and test-fixture measurement step by step. It can promote the fabricating yield if the designer pre-compensates the frequency shift due to influences have shown above. Lastly, a low voltage and wide tuning voltage controlled SAW oscillator (VCSO) at 433MHz is developed for wireless applications. The tuning capability is improved by using an impedance inverter. The spurious in the neighborhood are avoided by select carefully the reactance in the tank. The tuning range reaches 1.23MHz, it reveals good linearity from low voltage 2~8V. The modulation sensitivity is 190KHz/V。The current consumption under Vcc=8V is 7.2mA, the output power is about 10dBm. The phase noise is -120dBc/Hz at offset 10KHz.