超寬頻之表面聲波元件特性分析

Theoretical Analysis of Propagation Characteristics of Ultra-Wideband Surface Acoustic Wave Devices

張稟軍(Bing-Jun Zhang)

指導教授 ： 羅如燕

義守大學/電機資訊學院/電機工程學系/碩士(2016年)

摘要

本篇論文主要是利用COMSOL Multiphysics多重物理量耦合有限元素分析軟體以3D模組來進行探討六種不同切面方向、與十八種不同傳播角度的鈮酸鋰材料在平板結構時之波傳特性，其結構分為兩種，一種為電極/ LiNbO3，另一種則為電極/ LiNbO3/電極。分析出具有最佳波傳特性時之平板厚度、模態與材料後，再探討指叉換能器在不同材料、厚度、金屬化率對平板結構的機電耦合係數、表面聲波波速與反射係數之影響。經過模擬後，可以發現在電極/ LiNbO3/電極平板結構下，當傳播模態為SH0、平板厚度為0.1個λ、基板材料為30°YX-LiNbO3、電極材料為鋁厚度為0.0075個λ及金屬化率為0.3時有非常大之機電耦合係數70.61%，等效速度為3803.59 m/s，反射係數為0.28，可做為未來在設計應用於感知無線電系統中所需的可調式寬頻濾波器之基礎。

關鍵字

表面聲波元件 ； 鈮酸鋰 ； 機電耦合係數

並列摘要

This study focuses on how to use the finite element method (FEM) software Comsol Multiphysics to analyze the propagation characteristics of surface acoustic wave (SAW) devices. The substrate material used in this study is LiNbO3. Characteristics with different propagation directions and various cutting angles will be studied using Comsol Multiphysics 3D module. In addition, the effects of inter-digital transducers (IDTs) will be investigated. Two types of structures such as IDT/ LiNbO3 and IDT/ LiNbO3/IDT will be studied.
In this thesis, we determine the optimum thickness of the substrate plate with maximum coupling coefficient via the analysis of SAW characteristics at different thicknesses, different propagation modes, and different propagation directions. The effects of IDTs with different arrangements, different meal materials, various electrode thicknesses, and different metallization ratios on phase velocity, coupling coefficient, and reflectivity are then investigated.
Simulation results indicate that when the plate thickness is around 0.1 wavelength, the coupling coefficient is around 70%, which can be used to design the wideband filters for wireless communications applications.

並列關鍵字

SAW ； LiNbO3 ； coupling coefficient

參考文獻

[19] 陳昭昌 (1996)，有限元素法－工程上之應用，台南: 復文書局。

[1] Lord Rayleigh (1885). On waves propagated along the plane surface of an elastic solid, Proc. London Math. Soc., 17(1), 4-11.

[2] White, R. M., & Voltmer, F. W. (1965). Direct piezoelectric coupling to surface elastic waves. Appl. Phys. Lett., 7(12), 314-316.D.

[3] A. J. DeVries and R. Alder, “Case history of a surface-wave TV IF filter for color television receivers”, Proc. IEEE Vol. 64. pp. 671-676, 1976.

[4] R. M. Hays and C. S. Hartmann, “Surface-acoustic-wave devices for communications”, Proc. IEEE Vol. 64. pp. 652-669, 1976.