TY - GEN
T1 - High frequency resonators with excellent temperature characteristic using edge reflection
AU - Kadota, Michio
AU - Kimura, Tetsuya
AU - Tamasaki, Daisuke
PY - 2006/12/1
Y1 - 2006/12/1
N2 - 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.
AB - 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.
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U2 - 10.1109/ULTSYM.2006.474
DO - 10.1109/ULTSYM.2006.474
M3 - Conference contribution
AN - SCOPUS:78649386430
SN - 1424402018
SN - 9781424402014
T3 - Proceedings - IEEE Ultrasonics Symposium
SP - 1878
EP - 1882
BT - 2006 IEEE International Ultrasonics Symposium, IUS
ER -