Characteristics of surface acoustic wave coupler using quadrature unidirectional transducer structure

A new type of surface acoustic wave (SAW) coupler has been proposed, which is composed of a cascaded group type unidirectional interdigital transducer (UDT) structure to achieve desired performances without gratings and external phase shifters. In order to confirm the performances, simulations and experiments are applied. Predictions are also verified by simulations and experiments. A linear circuit composition procedure for multiport elements is applied in order to explain the meander resistive effect. Cascade-connected ports are prepared for the meander electrode. An improved cascaded UDT structure has been proposed to achieve wideband performances. A filter with a bandwidth twice as that of the conventional one is obtained. Furthermore the structure is applied to a Ring-type filter. High sidelobe rejection and low loss performances, and the miniature chip size of the filer are observed.