Design of overmoded-waveguide directional coupler and correction of coupling coefficient calculation

In order to satisfy the requirement of high-power microwave system, a novel overmoded-waveguide directional coupler centred at 2.4 GHz, with low coupling of 40–50 dB, and with directivity greater than 20dB, is designed. A resonant cavity as the transition waveguide between main waveguide and sub-waveguide is introduced. This paper also proposes a correction of coupling coefficient calculation. Ultimately, after optimizing the parameters, a structure with good performance is obtained.