Simulation of SAW waveguiding on substrates with asymmetric slowness and excitation

The 2D P-matrix method is extended to deal with SAWsubstrates with general slowness and excitation, asymmetric to main propagation direction. As described previously for general slownesses, which cannot be treated with the parabolic approximation, the problem of non-orthogonal transversal modes arises, which is treated by projection to adjoint modes . In the symmetric case modes were determined by demanding continuity of the mode and its derivative. In the asymmetric case this leads to the problem of diverging integrals of degenerate radiation modes. As a result radiation modes cannot be normalized. It is shown that by demanding continuity of the transversal power flow this problem can be solved. At the example of a resonator on lithium tantalate (YXl)/112.2 the validity of the new method is demonstrated. Another problem is the asymmetric propagation angle dependence of the phase between excitation and reflection, the directivity angle. By introducing an anisotropic phase shift into the transversal k-space excitation profile this effect is taken into account. At the example of a resonator on Quartz (YXl)/34.0 a good agreement with measurement is obtained.