Compact high power, high directivity, waveguide directional coupler utilizing reactively loaded junction

A directional coupler for coupling r.f. energy in a waveguide system from a main channel waveguide to a subsidiary channel waveguide, the coupling being in the range between about -3 dB to -15 dB. The coupler comprises a single coupling slot at the junction between the main channel waveguide and the subsidiary channel waveguide with an arrangement for decoupling the slot to yield the desired coupling, the arrangement including first and second posts in the plane of the junction. A further provision involves inductively loading the junction, the loading being provided at the plane of the junction. The provision for inductively loading the junction is an "inverted" button, in the form of capped-off holes, the depth of the holes being adjusted to vary the directivity of the coupler.