Four-Port Dual-Mode Diplexer with High Signal Isolation

Abstract

An ease of four-port dual-mode diplexer with high signal isolation is presented. A compact dual-mode diplexer with high signal isolation between the Rx and Tx modules is achievable by only using one resonator filter topology. Two back-to-back dual-mode diplexers have a 180° phase shift in one branch. The high isolation can be achieved by amplitude and phase cancellation technique. The delayed transmission line can be easily achieved by the phase shifter. The simulated and measured four-port dual-mode diplexers are designed at the centre frequency of Rx/Tx at 1.95 GHz and 2.14 GHz, respectively. The measured results of Rx/Tx dual-mode diplexer devices are presented with 47.1 dB Rx/Tx isolation. This four-port dual-mode diplexer achieves the isolation (S32) of more than 24.1 dB when compared with the conventional three-port dual-mode diplexer structure.

An Analysis of High Selectivity and Harmonic Suppression Based on Stepped-Impedance Resonator Structure for Dual-Mode Diplexer

“…Fig. 5(c) shows the wideband response compared with the conventional dual-mode resonator structure [17]. The stepped-impedance resonators are compact due to the slow-wave effect and have a wider upper stopband resulting from the dispersion effect.…”

“…Generally, when high signal isolation is required, a high-order resonator filter is needed, leading to a more complicated circuit. Another way to achieve high signal isolation is a four-port network [17]. However, this technique is still complex in structure and large circuits.…”