A General Synthesis Technique of Mixed-Topology Including Parallel-Connected Structures for Fully Canonical Ladder-Type Acoustic Filters

A synthesis method for mixed-topology fully canonical filters native oriented to acoustic wave (AW) technology is presented in this article. The method combines inline sections with parallel-connected structures to generate ladder-like networks. In regards to the classical ladder filters, this topology exhibits more flexibility in terms of transmission zeros (TZs) allocation above and below the passband by disassociating the TZs from the resonance frequency of the resonators. This degree of freedom can also be used as an advantage to accommodate the technology constraints of AW resonators. In addition to the general synthesis method, it is provided a set of considerations to be taken into account in designing a feasible filter for AW technology. To show the robustness and capabilities of the methodology proposed have been included two synthesis examples and experimental assessment by using an equivalent reactance Butterworth Van Dyke model for rapid prototyping.