S-parameter measurement-based asymmetric surface acoustic wave interdigital transducer characterization

Abstract

SAW (surface acoustic wave) resonators using asymmetrical interdigital transducers (IDTs) are experimentally characterized and its physical characteristics are modeled in terms of layout dimensions. It is shown that since the acoustic waves within a piezoelectrical material can be modulated by exploiting asymmetrical IDT layout variations, the physical characteristics of a SAW resonator (e.g., energy loss and out-of-band rejection characteristics) can be considerably improved. Test patterns for experimental characterizations are designed and fabricated with a LiTaO3 piezoelectric substrate. Then S-parameters are measured in a broad frequency band (50 MHz-6.05 GHz). The physical characteristics of an asymmetrical SAW IDT struc- ture are represented with a metallization factor (xi(i)) that indicates how much area the metal occupies within IDTs. Thereby, SAW-based microwave components can be designed efficiently with the asymmetrical IDT structures.