Stepped corrugation as a new type of TE11 to HE11 mode converter for corrugated horn antenna

A novel mode converter with stepped-slot structure is proposed and investigated for corrugated mode converter. The mode converter with the novel proposed slots provides low reflection compared to the other types of mode converters. The analysis, using mode-matching technique to determine the scattering matrix of the converter allows the return loss to be computed accurately. It is shown that a bandwidth ratio of 2.1 with return loss better than 25 dB is possible. The low-frequency performance of the converter is limited by the deterioration in return loss, while at high frequencies the generation of small amount of unwanted EH₁₂ mode is the restriction. If the effects of this mode can be neglected, operation over a wider bandwidth is possible, particularly for larger waveguide sizes.