Analysis of RF Wind Band Layered SAW Filter Using Slanted Finger Interdigital Transducer

• Main Authors: Lin, Chih-Ming, 林志明
• Other Authors: Wu, Tsung-Tsong
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/11586847604116888812

碩士 === 國立臺灣大學 === 應用力學研究所 === 91 === Abstract Today’s modern telecommunication systems require higher bit rate and larger transmitted data. This means that SAW filters tend to require wider bandwidth and higher frequency. Slanted finger interdigital transducer (SFIT) SAW filters could provide a frequency response with small pass-band ripple, flat and wide pass-band, large stop-band rejection, and steep cutoff characteristic. Hence, this type of filter may become a key element of telecommunication systems in the future. In this thesis, the coupling-of-mode (COM) model is used to analyze frequency response of SFIT SAW filters. The effective permittivity approach is used to calculate dispersive relation of layered structures. The effective permittivity approach and COM model are combined to analyze SFIT SAW filters on layered structures. As pointed out in the literatures, the amplitude response of SFIT SAW filters would incline in the pass-band due to the influence of transducer’s impedance. In this study, we propose a new method named “electromechanical coupling coefficient weighted” to flatten the inclination of pass-band by utilizing the dispersion of electromechanical coupling coefficient of IDT/AlN/Silicon layered structure. We also present other qualities of the layered SFIT SAW filters, such as increasing bandwidth or increasing center frequency. In the last part of this thesis, SFIT SAW filters with a variety of bandwidths are designed and fabricated on the YZ-LiNbO3 substrate. Good agreement between experimental and simulated results is obtained. Finally, we note that the result of this thesis may served as an important basis for analyzing layered SFIT SAW filters, which can be integrated with COMS process and used in wideband applications. Keywords: Slanted finger interdigital transducer, SFIT, Wideband SAW filter, Layered SAW filter, COM model, MEMS, Wireless communication