Effect of a narrow circular slot in a circular multimode waveguide on the propagation of symmetric electric waves in this waveguide

The prescribed-field method of Lapta and Sologub (1977) is used to analyze the E(0n)-mode S-matrix on a narrow circular slot in a circular multimode waveguide for all frequencies including the neighborhood of the critical frequencies. Frequency dependences of the elements of the S-matrix and the emission coefficient from the slot are obtained, and results are compared with results for H(0n)-mode scattering. It is concluded that the use of a narrow transverse circular slot as a reflecting element in an open cylindrical resonator makes it possible to tune the waveguide and to enhance the selection of adjacent modes.