A D-band Wideband High Isolation Diplexer

This study presents the design and simulation of a D-band wideband high-isolation hybrid diplexer tailored for future 6G communications. The diplexer, operating at 110–134 GHz and 146–170 GHz, features a hybrid configuration integrating high-low pass filters and hybrid couplers, achieving 20% and 15% relative bandwidths. The design optimizes gold's conductivity to minimize in-band insertion loss to approximately 0.5 dB and provides over 100 dB of inter-band isolation. Utilizing a double zero coupler, the diplexer enhances amplitude-phase imbalance and bandwidth performance. CST simulation software optimizes each component, and the integrated structure ensures high performance with minimal fabrication tolerances. Simulation results demonstrate exceptional port isolation and low insertion loss, showcasing the diplexer's suitability for advanced wireless systems.