A Universal Solution to ${\rm TM}_{11}$-to-${\rm HE}_{11}$ Circular Mode Converter Design

A universal solution to TM
₁₁
-to- HE
₁₁
mode converters in highly oversized circumferentially corrugated circular waveguides is proposed based on the nonuniform rational B-spline technique. A 35-GHz TM
₁₁
-to- HE
₁₁
mode converter of radius 16 mm is designed by the method and predicted to have a conversion bandwidth of 7.9% when the HE
₁₁
mode conversion efficiency is over 98.5%. The output mode content is extremely close to that of the ideal HE
₁₁
mode. The hot and cold tests show good property of the mode converter. The method offers universal solutions to the problems of the corrugated circular waveguide mode converters design at arbitrary radius and frequency.