Maximum Bandwidth Analysis With a Universal AWLR-Based Filter Structure

The bandwidth enhancement of the acoustic-wave-lumped-element resonator (AWLR)-based filter has been investigated for a long time. However, few researches are focused on the maximum bandwidth analysis. Based on a universal circuit structure of the AWLR-based filter, we proposed the maximum bandwidth analysis of the hybrid filter. In the analysis process, the universal filter structure can be transformed into a novel AWLR-based filter structure by incidentally excluding most of the other structures (including the reported hybrid filter structures) under the defined electrical characteristics. The novel hybrid filter obtains the maximum fractional bandwidth (FBW). Moreover, the proposed calculation results are better than the simulation results without artificial intervention. They are 2.12k_t² and 1.63k_t², respectively. k_t² is the electromechanical coupling coefficient of the acoustic wave resonator (AWR). Third-order AWLR-based bandpass filters with five-type circuit structures have been manufactured and measured. They include the proposed novel AWLR-based filter and the hybrid filter with the reported structure based on the universal AWLR-based filter structure. The experimental results indicate that the proposed novel AWLR-based filter has the maximum FBW.