SAW Device With Reactive Reflector for Integrated SAW RF Duplexer Area Minimization

A new integrated radio frequency (RF) duplexer design method is presented. To improve the skirt characteristics of a bandpass filter (BPF) and to reduce the die area of integrated RF duplexers, we developed a novel composite resonator design technique that can efficiently synthesize asymmetrical two surface acoustic wave (SAW) interdigital transducers (IDTs) with reactive reflectors. Adapting the technique for the design of an integrated RF duplexer, we can achieve much sharper resonance transition characteristics within a much smaller die area than previously possible. To verify the validity of the proposed techniques, we designed and manufactured several test resonators and duplexers by employing two representative SAW process technologies using the substrate of LiTaO₃ (conventional SAW and thin film (TF)-SAW). We experimentally show that the skirt characteristics of the BPF can be improved by 15%, and the die area of the test duplexer can be reduced by 20%.