Effects of electrode materials on natural unidirectionality of langasite

In this study, we carried out experimental research on the directivity of s urface acoustic wave (SAW) filters with Al, W and Ta electrodes formed on l angasite single-crystal wafers, in order to find electrode materials that m ake the natural unidirectionality disappear. The results proved that by usi ng W and Ta, the natural unidirectionality disappears at the normalized thi ckness (h/,lambda) of 0.033-0.037. This suggests a potential application of these metals as electrode materials for langasite-based SAW filters so tha t the design process of the single-phase unidirectional transducer (SPUDT) filter can be simplified by using tools for conventional SPUDT filters.