SAW substrate for Duplexer with Excellent Temperature Characteristics and Large Reflection Coefficient realized by using Flattened SiO{sub}2 Film and Thick Heavy Metal Film

摘要

Authors previously proposed a SAWPCS-duplexer with an excellent temperature coefficient of frequency (TCF) and a good frequency characteristic composed of a thick-SiO{sub}2/thin-Au-electrodes/LiTaO{sub}3 structure. However a sheet resistance of thin Au electrode is large, compared with thick Al-electrode, so thin Au-electrode is not suitable for filters requiring low loss. Authors tried to use thick Cu electrodes with small resistance By flattening large convex portions on the SiO{sub}2 surface, a SAW substrate suitable for US-PCS duplexer with low insertion loss and an excellent TCF was realized.