2D simulation of diffraction and reflection improves Z-path SAW filters for mobile communications

Z-path SAW filters are used to reduce the chip size of channel selection filters in mobile telephones. For these devices the conventional ID simulation methods are inappropriate as the SAW partly travels at an angle to the principal device axis due to the Z-shaped folding of the propagation path. We therefore use an approach which allows for the simultaneous analysis of diffraction, refraction and multiple reflections within the device. We demonstrate that the full 2D simulation is able to predict the insertion loss, the shape of the pass-band skirts, the stop-band level and the occurrence of spurious acoustic signals by comparing our results with the measured response of a Z-path device. Excellent agreement between measurement and simulation is obtained