Design of a circular TE5,1 mode generator for gyrotrons low-power measurement

摘要

To test quasi-optical mode converters for gyrotrons, an efficient low-power generator for rotating high-order modes with high purity is necessary. A W-band mode generator which converts a TE_(1,0) rectangular waveguide mode into either a linearly or a circularly polarized TE5,_1 circular mode is designed, fabricated, and measured. The generator consists of a mode converter, a waveguide transition, and a polarization converter. The converting process in each section is displayed and the working principles are discussed. The back-to-back measured results show that the conversion efficiency exceeds 63% with-2 dB from 92 to 95 GHz is obtained. The angle-independent transmissions demonstrate high-mode purity and the field pattern is directly demonstrated on a temperature-sensitive liquid-crystal sheet. The proposed mode generator features high-mode purity, easy to construct, and polarization controllability.