Design of transversal piezoelectric boundary acoustic wave filter for inverter drive circuit

Abstract To enhance isolation in gate-drive circuits for multilevel inverters, we proposed transversal piezoelectric boundary acoustic wave (PBAW) filters to replace previously used surface acoustic wave filters. First, we investigated transversal PBAW in a simple and easy-to-fabricate SiO 2 /Au/LiNbO 3 structure. Calculations demonstrated that reducing the number of electrode pairs enhances propagation characteristics; however, this structure does not effectively mitigate signal degradation. Therefore, we investigated the SiO 2 /Ta 2 O 5 /Au/LiNbO 3 structure, enabling better PBAW propagation. By optimizing with impedance matching, we achieved an insertion loss of less than 3 dB. To validate the feasibility of a transversal PBAW filter, we also experimentally investigated the SiO 2 /Au/LiNbO 3 structured PBAW filter. Using substrate cut angles and processes available within our research group, we fabricated and evaluated the prototype, confirming PBAW propagation. These results suggest that transversal PBAW filters exhibiting excellent propagation characteristics using SiO 2 /Ta 2 O 5 /Au/LiNbO 3 can be achieved with a precise Ta 2 O 5 fabrication process. The study offers a viable solution for enhancing isolation performance in gate-drive circuits.