Evaluation of directional couplers for high power gyrotrons

Abstract The formalism for analysing weakly coupled, aperture-type, mode-selective directional couplers is applied to the geometry of an end-fire high power gyrotron. A design procedure based on the constraints of a highly overmoded circular waveguide is presented. Several designs for a — 60dB, 9.85GHz, TE01 coupler are evaluated. Measurements of the forward and reverse coupling for the principal mode are found to be in good agreement with theory.