Design of a TE 11 - TE 21 Mode Converter Based on a Three-fold Helically Corrugated Waveguide

The mode converter based on a helically corrugated waveguide (HCW) presented in this paper is an important component for a gyrotron traveling wave amplifier. A three-fold right-handed (HCW) has been designed, which converted a left-hand circular polarized (CP) TE 11 mode to a right-hand CP TE 21 mode in the frequency range of 258-268 GHz. It achieved a transmission coefficient of better than -0.3 dB and a reflection below -30 dB.