Surface acoustic wave duplexer composed of SiO2 film with convex and concave on Cu-electrodes/LiNbO3 structure

Authors have already realized 3.0times2.5times1.2 or 2.5times2.0times0.48 mm³ size SAW duplexers for personal communication services in US with an excellent temperature coefficient of frequency (TCF) by using the Rayleigh wave on the SiO₂/Cu-electrode/ 120deg-128degYX-LiNbO₃ and 36deg-48degYX-LiTaO₃ structures. This time, authors intentionally attempted to make the convex portions on the SiO₂ film over the gap of interdigital transducers (IDTs). As the results, the calculated and measured results showed the increase of the reflection coefficient and the improvement of the TCF. In addition to them, the measured results showed that a power durability have been drastically improved without any deterioration in the frequency characteristics by making the convex portions on the SiO₂ film over the gap of the IDTs.