High Coupling and High Temperature Stable Surface Acoustic Wave Substrates Using Groove Type Interdigital Transducers

In this paper, in order to obtain the new substrates with the higher coupling of electromechanical coefficients(k(2)) and near zero temperature coefficients of frequency (TCF), the thin periodic grooves and interdigital transducers are fabricated on the high coupling substrates. The results showed high k2 over 0.4 at H/lambda =0.15 for rotated Y-cut, X-propagating LiNbO3 leaky SAW substrates, and high k(2) over 0.08 and small TCF of -10ppm/degrees C at H/lambda =0.1 and zero TCF at H/lambda =0.3, for 36 degrees Y-X LiTaO3 leaky SAW substrates. The groove type substrates are applied to resonator and nondispersive filters using dispersive unidirectional transducers. The experimental results of k(2) and reflectivities using grating groove resonators and UDT filters showed the good agreements to the theoretical ones.