Surface acoustic wave impedance element ISM duplexer: Modeling and opticalanalysis

Surface acoustic wave (SAW) impedance element antenna duplexers provide com pact, high performance. front-end components apt for industrial fabrication . We describe investigations on the design and modeling of a compact ISM an tenna duplexer fabricated oil a 36 degrees YX-cut LiTaO3 substrate based on SAW impedance elements. In particular. we have performed 3-D modeling of t he inductive and capacitive electromagnetic couplings caused by the package parasitics for the duplexer. The use of a 1:3 IDT structure for the reduct ion of the passband width is discussed. The frequency response of the duple xer is predicted with the help of circuit simulation: the modeling is refin ed by optimization of the model parameters to improve the fit between the m easured and simulated responses. We also report scanning optical imaging of the acoustic field within the resonator structures with the help of laser interferometry; this provides insight into the loss mechanisms beyond that attainable in mere electric measurements.