A Ultra-Wideband Slot Directional Coupler Based on S-ISCGW

A novel lantern-coupled microstrip 90° millimeter-wave ultra-wideband directional coupler based on symmetrically integrated substrate-coupled gap waveguide (S-ISCGW) is proposed. The directional coupler consists of a vertically symmetrical ISCGW, in which the lantern-coupled transmission line is coupled through a hexagonal coupling groove located on a common ground plane. The simulation results show that the band-width range of the directional coupler is 23.32~29.97 GHz, the relative bandwidth is 25%, the return loss is less than -20dB, the average isolation of the whole operating frequency band is greater than 26.5 dB, and a flat coupling of 3±0.35dB is obtained. The phase difference between the through port and the coupling port is 90°±0.46°.