A High- Isolation Quad-Channel Diplexer Based on Dual-Mode T-Shaped Resonators

In this paper, a high-isolation quad-channel diplexer is proposed with each path consisting of two folded dual-mode T -shaped resonators to reduce the circuit size and improve passband isolation. Due to the controllable transmission zero and resonant frequency of the T -type resonator, it can achieve quad controllable channels with good frequency selectivity in the receiving and transmitting channels. To confirm the feasibility of the theoretical design, we designed, fabricated, and measured prototypes of the diplexer. The measured results of the circuit are in good agreement with the simulation results.