Low Loss Directional Coupler with Dual Phase Shifters for sub-6 GHz RF Front-End Modules

抄録

In this work, wideband radio-frequency (RF) bi-directional couplers with phase shifters (PS) for low insertion loss are presented. Conventional narrowband directional couplers have limited bandwidth because of excessive power loss due to strong coupling at high frequencies. To alleviate this issue, a directional coupler employing a phase shifter has been proposed. However, the analytical equation of main-line insertion loss has not been derived so far. The insertion loss equations for a coupler consisting of two coupled lines and one phase shifter is derived and presented. To achieve further loss reduction, we propose a coupler in which the coupled lines are divided into three sections and two phase shifters are inserted. Simulation and measurement results confirm that the coupler with two phase shifters achieves significantly lower insertion loss (IL) at high frequencies and enables broadband operation.