Design and Study of Surface Acoustic Wave Filters

• Main Authors: Mei-Hui Chung, 鍾美惠
• Other Authors: Shuming Wang
• Format: Others
• Language: zh-TW
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/08241098867904266416

碩士 === 義守大學 === 電機工程學系 === 88 === Surface acoustic wave (SAW) filters consist of pairs of interdigital transducers (IDTs) fabricated on piezoelectric substrates. The properities of substrate, the modes of wave propagation, the geometry and position of IDTs determine the characteristics of SAW filters. In the thesis, the Mason’s equivalent circuit model, the cascade model and the theory of multiport connection were applied to simulate different structured SAW filters. As an example, the IF filters used in DECT system was chosen. The specifications are as follows: the center frequency is 112.32MHz, the minimum 3dB-bandwidth is 1.1MHz, the maximum 40dB-bandwidth is 6.9MHz, and the maximum insertion loss is 12dB. ST-X quartz substrate is used. Different IDTs structures, such as uniform weighting, apodized weighting, and withdraw weighting, are fabricated. The simulation and experimental results were compared. The effect of various weighting on the frequency response, input and/or output impedance, group delay, etc. of SAW filters ware thoroughly studied. Finally, the procedure and reliable simulation computer program of SAW filters were established.