Mode coupling due to curvature in circumferentially corrugated circular waveguides is analyzed in this paper. Starting from Maxwell's equations in the annular orthogonal curvilinear coordinate-system, the integral formulae for coupling coefficients are derived. On the basis of them, the explicit expressions of coupling coefficients between positive or opposite modes are derived.
Thumm, M 李宏福.弯曲波纹圆波导中模式耦合系数的研究[J].红外与毫米波学报,1992,11(6):486~491]. Li Hongfu, Manfred Thumm. STUDY ON MODE COUPLING COEFFICIENTS IN CURVED CORRUGATED CIRCULAR WAVEGUIDES[J]. J. Infrared Millim. Waves,1992,11(6):486~491.]