Symmetric waves in a circular metal waveguide containing an anisotropically conducting coaxial cylindrical surface

Symmetric waves propagating in a hollow metallic waveguide that contains a coaxial cylindrical surface which conducts perfectly along helical lines with a small twist angle are investigated. It is found that, at certain ratios between the structure’s geometric parameters, there exist two modes with close propagation constants. It is shown that the superposition of these modes results in a field that, during propagation along the waveguide, periodically coincides either with the field of the E ₀₁ mode of the inner cylindrical channel (in this case, the field is zero in the coaxial area) or with the field of the H ₀₁ mode of the outer channel. A circular-waveguide E ₀₁ ? H ₀₁ mode converter has been developed and experimentally investigated. It is shown that the conversion loss does not exceed 0.8 dB.