Synthesis Guidelines for Acoustic Wave Standalone Ladder Filters with Dual-Band Responses

This work aims to describe the synthesis guidelines for a dual-band filter with the conventional ladder structure, currently only used in single-band acoustic wave filters. Current commercial design approaches of dual-band filters based on piezoMEMS are strongly constrained in the achievable out-of-band rejection as the usual strategy is to connect in parallel different filters. When in fact, the ladder structure itself is capable to implement a dual-band response with high performance. However, pursuing the synthesis of the dual-band filter as a fully in-line ladder structure requires careful attention in the arrangement of resonators, issue that will be covered in this paper.