Compact broadband couplers based on the waveguide magic-T junction

In this paper, a broadband 180° waveguide directional coupler based on a modified magic-T junction is presented. The well-known magic-T waveguide junction is effectively modified and optimized leading to enhanced performance. Moreover, the volume of the proposed enhanced magic-T is similar to the classic junction. The novel magic-T proposed uses an iris in the E port, a single width step in the H port, a simple post in the junction and reduced height in the H and common ports. The bandwidth of the directional coupler can be significantly enlarged with a proper optimization of these four key elements. Different designs are presented covering the full standard rectangular waveguide band, over 40% relative bandwidth, with more than 25 dB return loss in the four ports. In addition, a compact bend with integrated transformer is introduced at the input/output interfaces.