IDENTIFICATION OF HIGH-VELOCITY PSEUDO-SURFACE ACOUSTIC WAVE SUBSTRATE ORIENTATIONS AND MODELING OF SURFACE ACOUSTIC WAVE STRUCTURES

A detailed analysis is presented for calculating the per-strip admittance of periodic electrode gratings on piezoelectric substrates. Based on this analysis, a new method is described for identifying substrate orientations along which low-attenuated, stronglycoupled high-velocity pseudo-surface acoustic waves (HVPSAWs) exist. An extensive search for HVPSAW orientations of lithium niobate (LNO) and lithium tantalate (LTO) is reported, and new HVPSAWorientations are identified. Dispersion properties for periodic gratings comprised for aluminum, gold, and platinum electrodes along various orientations of LTO are presented. Simulated and measured electrical responses of HVPSAW devices along these orientations are nearly identical. A detailed analysis of bulk acoustic waves (BAWs) radiated by interdigital transducers (IDTs) and the angular distribution of acoustic power is presented. The effect of mass loading by finite thickness electrodes on transducer efficiency is quantified. A rigorous analysis of the acoustic scattering properties of finite periodic gratings is detailed. Based on this analysis, a new method for determining surface acoustic wave (SAW) network model (NM) parameters is presented. The resulting network model is applicable to arbitrary substrate orientations, including those which exhibit the natural single-phase unidirectional transducer (NSPUDT) effect. Network model simulations and measured electrical responses of two-port SAW resonators devices along both symmetrical and NSPUDT orientations agree very well. An augmented network model for SAW structures is presented which incorporates radiation and scattering of bulk acoustic waves. This new model precisely mimics pseudo-SAW and HVPSAW behavior in periodic electrode structures.