This paper describes a design procedure for surface acoustic wave (SAW) filters using slanted finger interdigital transducers (SFIT) that are suitable for midband or wideband applications. The SFITs cannot represent the impulse response directly, in contrast to apodized IDTs. A design method for SFITs based on a building-block approach in the frequency domain is described. An automatic computer-aided design tool for SFIT filters has been achieved. The SFIT filters can be designed using a withdrawal weighting for stop-band responses, an aperture weighting for pass-band amplitude responses, and a distance weighting for pass-band phase responses. In addition, an SFIT pattern for photo mask can be automatically designed using this tool. Using this tool, an SFIT filter with a relative bandwidth of 15% was designed on an x-cut 112y-direction LiTaO3 substrate.
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