Coupling between waveguide and hemispherical open resonator

The hemispherical open resonator feeding by the rectangular waveguide was analyzed by using the modal analysis method. The open resonator was excited by the rectangular waveguide through a narrow slot, with a complete analysis of all the relevant modes in the waveguide and the open resonator, the coupling coefficients according to the difference width slots were derived among Ka waveband, further more, the coupling coefficients of a slot at different eigen frequency were calculated and were compared to experimental results.