Exact calculations of scattering parameters of a step slot width discontinuity in a unilateral fin-line

The dominant and the first four higher-order modes in a unilateral fin-line are accurately described from a thorough spectral-domain approach. Then, coupling coefficients between eigenmodes at a step slot width discontinuity to be used in the generalised scattering matrix formulation are directly computed in the spectral domain. Scattering parameters of the dominant mode in the Ka band are presented.