High precision simulation of broadband SAW filters

A full two-dimensional simulation model for broadband SAW (surface acoustic wave) filter has been developed using the technique of modular modeling. The model takes into account the second-order effects caused by wave diffraction and refraction, two-dimensional static charge distribution, metal resistance, and external load impedances. The angular spectrum formalism is generalized to allow the description of all effects mentioned. The simulation of a LZ LiNbO₃ filter with an aperture of 80 λ and a relative bandwidth of 41% shows an excellent agreement with the measurement. The agreement in the passband is better than 0.1 dB, and the stopband approximation is also shown to be excellent