ABSTRACT The propagation characteristics of surface acoustic waves (SAW) and piezoelectric leaky surface waves in KNbO3 single crystal have been investigated theoretically and experimentally. The results show that the electromechanical coupling coefficient k2 of the surface wave propagating along the X-axis of the rotated Y-cut plate is very large with k2=0.53. This is about 10 times as large as that of LiNbO3 in the surface wave branch. Experimental results for wideband SAW filters show low loss and temperature stable characteristics. The bandwidth is about 20%, and insertion losses are less than 2 to 6 dB. Simulation results for a ladder type filter using Y-cut KNbO3 indicate that a bandwidth of 40% should be possible. The KNbO3 substrates exhibit zero temperature coefficient of frequency (TCF) around 20oC in rotated Y-cut substrates.
1999 IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control Vol. 46, pp. 700-705, 1999
© 1999, by The Institute of Electrical and Electronics Engineers, Inc. All rights reserved.