Mode coupling in a planar circular waveguide array

By means of an integral-equation approach, expressions are derived for all mode coupling occuring in a finite, planar circular waveguide array. Modes coupling in the aperture of each waveguide yield terms dependent upon contour integrals. These are placed in a suitable form for numerical integration. A new asymptotic formula is obtained for the coupling between modes in separate waveguides. Theoretical results are presented for the TE11 mode admittance of flanged circular waveguide and for two waveguides coupling in the H-plane. These results are shown to correlate satisfactorily with previously published experimental data.