Investigation of surface-acoustic-wave bandpass filters based on nonaperture-weighted interdigital transducers

Surface-acoustic-wave (SAW) filters based on nonaperture-weighted interdigital transducers (IDTs), i.e., transducers in which the amplitude weighting is performed by the variation of the strip-width-to-gap-width ratio, are theoretically investigated. It is shown that filters with nearly symmetric frequency responses with high out-of-band-suppression levels can be obtained by compensating for the spatial dispersion of the SAW velocity during the design of the electrode structure of the IDTs. The comparison of these filters with apodized filters is performed in the case when the coordinates of the electrodes are subject to random dispersion.