Mode converters used in the Doublet III ECH microwave system†

Abstract

Woveguide mode converters aro used in the 60 GHz, 200 KW plasma heating system for Doublet III both to convert from the TE₀₂ to the more convenient. TE₀₁ mode for transmission and to convert from the TE₀₁ to the TE₁₁mode to produce a linear polarization at the antenna. Both converters line periodic wall porturbations, the former having circularly symmetric perturbations and the latter periodic curvature (m = 1) perturbations. The TE₀₂ to TE₀₁ converter shows a conversion efficiency of at least 95% (99% predicted) while the TE₀₁ to TE₁₁ convertor has a 90% conversion efficiency (92% predicted). The frequency sensitivity of these devices will be discussed.