Super high electromechanical coupling and zero temperature coefficient surface acoustic wave substrates in KNbO(3) single crystal.
The propagation characteristics of surface acoustic waves (SAW) and piezoelectric leaky surface waves in KNbO(3) single crystal have been investigated theoretically and experimentally. The results show that the electromechanical coupling coefficient k(2) of the surface wave propagating along the X-axis of the rotated Y-cut plate is very large with k(2)=0.53. This is about 10 times as large as that of LiNbO(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(3) indicate that a bandwidth of 40% should be possible. The KNbO(3) substrates exhibit zero temperature coefficient of frequency (TCF) around 20 degrees C in rotated Y-cut substrates.
Yamanouchi
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Res. Inst. of Electr. Commun., Tohoku Univ., Sendai, Japan. yamasaw@riec.tohoku.ac.jp
Odagawa
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