  Waveguide directional couplers working at 5.712/11.9924 GHz are developed.
Even holes symmetrical to the structure are drilled along the central line of
the narrow-wall of waveguide, which are used to couple the electromagnetic
power from the main-waveguide to the sub-waveguide. The final prototypes have
got satisfactory performances of high-power, ultra-high-vacuum and
high-directivity. The microwave measurement results are also qualified.
