Compact 10 dB broadband directional coupler

This paper proposes a compact 10 dB broadband directional coupler, which is constructed from two parallel E-plane rectangular waveguide with three apertures and three metallic posts attached on the apertures. The design has been simulated using Computer Simulation Technology (CST) Microwave Studio 3D simulator, the simulation shows that return loss of the compact directional coupler is below -25 dB between 7.7 GHz and 12.1 GHz, the coupling is 10.1±0.8 dB and the isolation is better than 38 dB in a fractional band of 44%. In order to measure and match the directional coupler, a waveguide-to-waveguide transition has been proposed, whose return loss is below -27 dB in the design band.