Design of High-Isolation Topological Duplexer Utilizing Dual-Edge State Topological Waveguides

Topological edge states have gained significant attention due to their exceptional capability to transmit signals without being affected by defects, which make them promising for applications in microwave and terahertz integrated circuits. In this paper, supercell structures based on topological photonics crystals (TPCs) under dual-edge state are proposed. The energy bands of the proposed supercells is different from those of traditional supercells in that they exhibit forbidden band gaps in addition to edge state and bulk state, facilitating an effective out-of-band rejection filter function through the use of dual-edge state transmission. The robustness of this new structure against bends and fabrication defects has been experimentally validated. To demontrate the feasibility of the proposed structure, we design and realize a topological duplexer which delivers superior transceiver performance and exceptional isolation capabilities. The duplexer is configured with two distinct channels (first channel spanning from 13.20 GHz to 13.43 GHz while the second one ranging from 13.88 GHz to 14.25 GHz), offering isolation of exceeding 27 dB and reaching up to 35 dB. The research findings offer flexible approaches for implementing frequency selection applications, serving as a reference for the future designs and application of integrated package duplexers.