Title :
Super high electromechanical coupling and zero temperature coefficient surface acoustic wave substrates in KNbO/sub 3/ single crystal
Author :
Yamanouchi, Kazuhiko ; Odagawa, Hiroyuki
Author_Institution :
Res. Inst. of Electr. Commun., Tohoku Univ., Sendai, Japan
fDate :
5/1/1999 12:00:00 AM
Abstract :
The propagation characteristics of surface acoustic waves (SAW) and piezoelectric leaky surface waves in KNbO/sub 3/ single crystal have been investigated theoretically and experimentally. The results show that the electromechanical coupling coefficient k/sup 2/ of the surface wave propagating along the X-axis of the rotated Y-cut plate is very large with k/sup 2/=0.53. This is about 10 times as large as that of LiNbO/sub 3/ 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 KNbO/sub 3/ indicate that a bandwidth of 40% should be possible. The KNbO/sub 3/ substrates exhibit zero temperature coefficient of frequency (TCF) around 20/spl deg/C in rotated Y-cut substrates.
Keywords :
ladder filters; piezoelectric materials; potassium compounds; substrates; surface acoustic wave filters; surface acoustic waves; 2 to 6 dB; KNbO/sub 3/; KNbO/sub 3/ single crystal; SAW filter; Y-cut substrate; electromechanical coupling coefficient; ladder filter; piezoelectric leaky surface wave propagation; surface acoustic wave propagation; temperature coefficient of frequency; Acoustic propagation; Acoustic waves; Bandwidth; Frequency; Insertion loss; SAW filters; Surface acoustic waves; Surface waves; Temperature; Wideband;
Journal_Title :
Ultrasonics, Ferroelectrics, and Frequency Control, IEEE Transactions on
