Superhigh Electromechanical Coupling and Zero-Temperature Characteristics of KNbO 3 and Wide Band Filter Applications
- 1 May 1998
- journal article
- Published by IOP Publishing in Japanese Journal of Applied Physics
- Vol. 37 (5S)
- https://doi.org/10.1143/jjap.37.2929
Abstract
In this paper, a superhigh electromechanical coupling surface acoustic wave (SAW) propagating on a potassium niobate (KNbO3) substrate is described and its applications for low-loss, wide band and temperature stable SAW filters are investigated. KNbO3 has large piezoelectric constants. We obtained the electromechanical coupling coefficient (K 2) of 0.53 for SAW in a Y-cut X-propagating substrate, theoretically and experimentally. It is observed to be about 10 times as large as that in LiNbO3. Moreover, we obtained the zero temperature characteristics around room temperature, in a rotated Y cut substrate. The experimental results of the wide band SAW filters show low loss and stable temperature characteristics. The bandwidth is about 20% and the insertion losses are less than 2–6 dB. The simulation results of a ladder-type filter using the Y-cut KNbO3 show a bandwidth of 40%.Keywords
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