A four-pole SAW resonator filter combining transverse and symmetrical longitudinal modes

As a continuation of the activities concerning longitudinal and transverse modes, this paper describes the combination of transverse and neighboring longitudinal modes with the same symmetry for designing a four-pole resonator filter. The construction of both interdigital transducers arranged side by side agrees and is characterized by a symmetrical withdrawing weighting. The present solution offers the advantage to achieve a wider bandwidth for the same layout dimensions compared with the principle using neighboring longitudinal modes of different symmetry. The applicability of the principle to the filter design is demonstrated by experimental measurements.