Design of Compact Balanced-to-Balanced Diplexer Using Dual-Mode CRLH Resonator for RFID and 5G Applications

A compact balanced-to-balanced diplexer based on composite right/left-handed (CRLH) resonator is presented in this paper. The proposed compact CRLH resonator is used to design two balanced channels, which are connected by T-junction to construct the balanced-to-balanced diplexer. Under differential-mode (DM) operation, the proposed CRLH resonator can provide two adjacent DM resonant modes to produce one passband of the balanced-to-balanced diplexer. Under common mode (CM) operation, the CRLH resonator also generate two CM resonant modes, whose locations are far away from DM resonant modes, resulting in a perfect CM suppression level. To verify the design methodology, a compact balanced-to-balanced diplexer operated at 2.45 GHz and 3.47 GHz is designed and fabricated for multi-service system integrated with microwave RFID and 5G applications. The proposed balanced-to-balanced diplexer shows high CM suppression level and channel-to-channel isolation performance. The measured results are agree well with the simulated ones.