Miniaturized A1 Mode Acoustic Resonators and Filters Using Inverted T-Shaped Electrodes

This work presents miniaturized first-order antisymmetric (A1) mode acoustic resonators and filters utilizing inverted T-shaped electrodes (ITEs) to enhance static capacitance density and improve power handling of thin-film A1 mode devices, targeting high-frequency compact RF front-ends. Comprising a double-layer electrode, the proposed ITE structure decouples the mass loading from electric boundary, enabling an increased metallic ratio (MR) while avoiding spurious modes. Based on a Z-cut LiNbO₃/Si substrate, resonators and filters with single-layer electrodes (SLEs) and ITE are fabricated. The resonators with ITE show a maximum increase of 95.8% in static capacitance density and an increase of ab out 4 dBm in power handling compared to the one with SLE while keeping the response from deteriorating. The filter with ITE exhibits a fractional bandwidth (FBW) of 12.5% at the center frequency of 5.245 GHz and a power handling improvement of 3 dBm compared to the filter with SLE. Concurrently, the area of the resonators with ITE in the filter is reduced by 53.8% and 51.4% compared to resonators with SLE. Overall, the novel structure of ITE shows great potential in increasing static capacitance density and power handling, contributing to the miniaturization of RF acoustic resonators and filters.