A Synthesis Approach to Acoustic Wave Ladder Filters and Duplexers Starting with Shunt Resonator

Eloi Guerrero, Patricia Silveira, Jordi Verdu, Yansong Yang, Songbin Gong, Pedro De Paco

Research output: Contribution to journalArticlepeer-review

Abstract

In this article, we explore how acoustic wave filters starting with shunt resonator require particular reflection phase conditions to ensure that the synthesized filter is feasible. The position of transmission zeros (TZs) along with the phase of the objective filter function might lead to nonfeasible solutions where the first and last resonators require elements with positive reactance slope in the static branch, or equivalently, a nonphysical negative static capacitor. Since the reflection phase of a duplexer-oriented filter is fixed to reduce loading effects, the feasibility problem is solved by bringing the resonance frequency of the first resonator beyond the central frequency of the counter band. However, this entails surpassing the limits of the electromechanical coupling coefficient. We demonstrate how two reactive elements at the input overcome this resonance position limitation and provide a simple rule to decide the right topology. The position of the first TZ of duplexers will play an important role. Moreover, we provide rules on the reflection phase values that ensure that all resonators have a capacitive static branch.

Original languageEnglish (US)
Article number9250624
Pages (from-to)629-638
Number of pages10
JournalIEEE Transactions on Microwave Theory and Techniques
Volume69
Issue number1
DOIs
StatePublished - Jan 2021

Keywords

  • Acoustic wave (AW)
  • duplexer filter
  • filters
  • reflection phase
  • synthesis methodology

ASJC Scopus subject areas

  • Radiation
  • Condensed Matter Physics
  • Electrical and Electronic Engineering

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