High frequency resonators with excellent temperature characteristic using edge reflection

Michio Kadota, Tetsuya Kimura, Daisuke Tamasaki

Research output: Chapter in Book/Report/Conference proceedingConference contribution

7 Citations (Scopus)

Abstract

Most surface acoustic wave (SAW) radio frequency (RF) filters and duplexers have the Al-electrodes/36-48°YX-LiTaO3 substrate structure, which has an optimum coupling factor and an optimum reflection coefficient but does not have a good temperature coefficient of frequency (TCF). The TCF can be improved by depositing SiO2 film with positive TCF on a transversal SAW filter consisting of a substrate with negative TCF such as LiTaO3 and LiNbO3. However, resonator-type SAW devices combining SiO 2 film, Al electrodes, and LiTaO3 substrate do not show a good frequency characteristics regardless of Al thickness. Because both (a) a SiO2/thin Al-electrodes/LiTaO3 structure with small convex portions on the SiO2 surface and (b) a flattened SiO 2/Al-electrodes/LiTaO3 structure have a small reflection coefficient, and (c) a SiO2/thick Al-electrodes/LiTaO3 structure with large convex portions has a small coupling factor. It is considered as a counter-measure that a resonator using the reflection of a shear horizontal (SH) wave at substrate edges of their structures shows a good frequency characteristic because its reflection coefficient is very large regardless of Al thickness. It has been difficult to obtain a high-frequency edge reflection resonator because it requires too fine substrate edges for ordinary machining techniques. However, a high-frequency edge reflection resonator with a good TCF and an excellent frequency characteristic has been realized using our newly developed method of obtaining fine edges.

Original languageEnglish
Title of host publication2006 IEEE International Ultrasonics Symposium, IUS
Pages1878-1882
Number of pages5
DOIs
Publication statusPublished - 2006 Dec 1

Publication series

NameProceedings - IEEE Ultrasonics Symposium
Volume1
ISSN (Print)1051-0117

ASJC Scopus subject areas

  • Acoustics and Ultrasonics

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