Symmetrical Quasi-Absorptive Filter Based on SAW Resonators and Lumped Elements

A symmetrical quasi-absorptive bandpass filter (BPF) based on hybrid blocks of surface-acoustic-wave (SAW) resonators is proposed. The resonant frequencies of the SAW resonators are decoupled by additional lumped elements. The topologies of the even-/odd-mode equivalent circuits have been analyzed to synthesize the quasi-absorptive behavior. To verify the design approach, a prototype is designed with a center frequency of 916 MHz, which achieves a bandwidth of 2.3 MHz and a good quasi-absorptive property.