Dispersion curves for 128 Lithium Niobate, YZ Lithium Niobate, 42 Lithium Tantalate, STX Quartz, STX+25 Quartz, ATX Quartz, and LGS crystals are calculated with modified Hasimoto's program. Dependences of obtained COM parameters on the electrode width and thickness are approximated by polynomials and used for calculations of admittance of transducer and frequency response of surface acoustic wave device by P matrix technique. The modified soft allows to calculate any substrates, including ones with low electromechanical coupling coefficients, those are very difficult or even impossible for calculation by means of other known tools.
The paper deals with the derivation of simple polynomials characterising surface acoustic wave (SAW) reflection by metallic gratings with various widths and thicknesses. Such polynomial approximation makes it possible to estimate coupling of mode (COM) parameters in markedly reduced computational time. For very sophisticated SAW devices, this is of great use to develop high-speed simulation and design tools based on the COM method. In the present study, it is shown how simply and accurately the SAW reflection by aluminium gratings on 128°YX-LiNbO3 substrates or 36°YX-LiTaO3 substrates is characterised by polynomial approximation.
We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero.