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Wide-band surface acoustic wave (SAW) filters using single-phase unidirectional interdigital transducer (SPUDT) showed promise to achieve low loss and high selectivity. In this paper, the SAW filters were studied via finite element method (FEM) using 2D models and utilized YZ-LiNbO3 for piezoelectric substrate. | Journal of Science and Technology 123 (2017) 014-018 FEM Analysis of High-Selectivity SAW Filter using SPUDT Structure 2 Tran Manh Ha1,2, Do Quang Huy1, Hoang Si Hong1, Nguyen Thi Hue1* Hanoi University of Science and Technology, No. 1, Dai Co Viet, Hai Ba Trung, Hanoi, Viet Nam The Vietnam Research Institute of Electronics, Informatics and Automation, 156A Q.Thanh Str, Hanoi, Vietnam Received: August 30, 2017; Accepted: November 03, 2017 1 Abstract Wide-band surface acoustic wave (SAW) filters using single-phase unidirectional interdigital transducer (SPUDT) showed promise to achieve low loss and high selectivity. In this paper, the SAW filters were studied via finite element method (FEM) using 2D models and utilized YZ-LiNbO3 for piezoelectric substrate. With respect to the investigated center frequencies of 97 MHz and 179 MHz, the SPUDT SAW filter demonstrated low power losses (26.85 dB and 22.63 dB respectively) and high attenuation band (12.73 dB and 23.95 dB) in comparison to the bidirectional SAW filter. It was also identified that the changes in different electrode factors including the material, the thickness, and the quantity had influences on the SPUDT-type filter response. Keywords: SAW filter, SPUDT, FEM 1. Introduction * properties [1, 2, 9]. The common disadvantage of these methods is that they require the parameters that could be only determined from experimental process or numerical determination [10]. Among existing simulation methodologies, finite element method (FEA) is considered as the most accurate technique for SAW devices analysis without fabrication [5]. Elsherbini and Ionescu used FEM to simulate SAW one-port resonators and focused their applications on sensing systems [5, 11]. Typical SAW filters based on bidirectional transducer structure (Bi-IDT) are affected by internal reflection among interdigital transducers (IDTs) [1, 2], which depends on the thickness and materials of electrodes [3], not only causing multiple-transit .
