Acoustic Wave Multiplexer Modules: A Completely Analytical Synthesis Method

This work discusses a filter synthesis method for multiplexers composed of acoustic wave ladder filters. Extending previous synthesis techniques for ladder filters, this method is devised to compute the Butterworth - Van Dyke elements of all resonators composing the multiplexer. To do so, the method leverages on the computation of a multiport filter function that describes the complete response of the multiplexer in polynomial terms and finds the elements that implement such function. In this work, the rationale behind such functions is described and a synthesized quadplexer example is provided as a demonstration. Thanks to a synthesis approach, a seed design of the multiplexer fulfilling technological requirements can be obtained analytically avoiding costly optimization stages.