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.

The use of classical symmetrical polynomial definition to synthesize fully canonical inline filters with an asymmetrical distribution of the transmission zeros along the topology leads to the occurrence of uneven admittance inverter in the main-line. This form introduces some limitations to transform such topology into a ladder network. Despite circuital transformation can be used to accommodate both technology and topology, it is usual that extra reactive elements are necessary to implement phase shifts required to achieve the complete synthesis. This article introduces a novel method able to determine the required phase correction that has to be applied to the characteristic polynomials in order to equalize all the admittance inverters in the main path to the same value. It has been demonstrated that a suitable pair of phase values can be accurately estimated using a developed hyperbolic model which can be obtained from the transmission and reflection scattering parameters. To experimentally validate the proposed method, a Ladder-type filter with asymmetrical polynomial definition has been synthesized, fabricated, and measured, demonstrating the effectiveness of the developed solution.