Mode selective directional couplers in overmoded circular waveguides

Abstract

Mode selective couplers for overmoded waveguides were developed for transmission line systems between gyrotrons and plasma experiments to measure the mode composition. The directional couplers are either based on constructive interference of wanted mode amplitudes or destructive interference of unwanted mode amplitudes. Four-hole cross couplers serve as monitors for the contents of asymmetric modes and the orientation of their field vectors in the circular waveguide.