The impulse model including waveguiding effects using modal analysis

For filter design and analysis, the impulse model is a very fast and powerful tool. Based on transverse mode analysis the impulse model has been expanded to account for the influence of the different metallization regions in a transducer. Using a simple waveguide representation, a modified Fourier series decomposition is applied to determine the contribution of an interelectrode gap source to the propagating modes. The influence of different transverse positions of the inter-electrode gap in the waveguide structure is treated, providing valuable insight into the propagation of modes. The array factor, normally used in the impulse model, is modified according to the mode weighted gaps. The transducer is divided up in regions where the normal impulse model is used. Therefore, the transducers analyzed do not have to be an ideal waveguide in the total length. The agreement between measurement and model predictions of the sidelobe levels is quite good, keeping in mind the assumptions made