The Research of Surface Acoustic Wave Coupled Resonator Device

• Main Authors: Yuan-Bo Huang, 黃元伯
• Other Authors: Cheng-liang Huang
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/90076757449472866115

碩士 === 國立成功大學 === 電機工程學系碩博士班 === 91 === SAW CR filter posses narrow bandwidths (typically 0.03% to 0.6%), low insertion loss, and good ultimate rejection without harmonic spurious responses. The past paper discusses mostly CR filter, which is band-pass filters. Band-rejection CR filters neglect in the past. In this research, we use the Coupled-of-mode theory to model the frequency response of the SAW CR band-rejection filters and discuss the influence of number of IDT electrode, length of overlap, and delay-line distance on the frequency response. In this experiment we know CR filter which has three type of coupled-mode. One type is under- coupled and other are matched and over-coupled. It affect by the number of center grating. With number of IDT electrode increase, insertion loss becomes smaller. But curvature of pass-band response becomes to curve. It is worse to band-rejection filters. When length of overlap increases, shape of filter response does not change so much. And pass-band rejection maintains to 35dB, stop-band rejection maintain 19dB. Delay-line is a major factor in distributing the surface acoustic wave. When delay-line is 3/8λ, SAW device becomes band-pass filters. However delay-line is 1/8λ, SAW device work as band-rejection filters. We can improve the frequency response and low the insertion loss, so appropriate design of the delay-line will be important. According to the discussion of above, a good band-rejection filter is manufactured by using less the number of IDT electrode and suiting delay-line distance and more longer the length of overlap.