Theoretical analysis of SAW propagation characteristics under the strained medium and applications for high temperature stable high coupling SAW substrates

摘要

The important properties required for SAW substrates are a large electromechanical coupling coefficient (k/sup 2/), small temperature coefficient of frequency (TCF), low propagation loss, etc. LiNbO/sub 3/ and LiTaO/sub 3/ have good properties as SAW substrates with a large size. Unfortunately these possess the disadvantage of large values of TCF. In this paper, SAW bonded composite substrates with a large k/sup 2/, small TCF, low propagation loss and no dispersion using conventional bonders are investigated theoretically and experimentally. The propagation characteristics of SAW under the strained piezoelectric crystal using the higher-order elasticity theory have been analyzed. The theoretical results show zero TCF on LiNbO/sub 3//SiO/sub 2/ substrates. The experimental results of LiNbO/sub 3//glass substrate showed TCF of 19 pptn//spl deg/C. The propagation properties were almost the same as those of the single crystal.