Enabling Microwave-Acoustic Ladder Filters Feasibility by Bounded Filter Reflection Responses

This paper explores a general ladder AW filter synthesis methodology that allows to trade the depth of the reflection zeros for greater flexibility to accommodate technological constraints. The method proposes arranging the RZs in the complex plane in such a way the device performs equiripple in band but having RZs not so deep as expected for a generalized Chebyshev function with finite transmission zeros. A validation example reaches a common electromechanical coupling coefficient for a set of resonators with an out-of-band rejection close to that achievable with an ideal equiripple response that will require different electromechanical coupling coefficient and then external reactive elements.