In the gyrotron traveling wave amplifier (gyro-TWA), high loss dielectric materials loaded in a cylindrical waveguide are adopted to suppress the unwanted parasitic oscillations. It is of great importance to accurately understand the relative permittivity εr and tanδ for studying the microwave and millimeter wave dispersion, and loss properties of a specific mode. The high lossy dielectric loaded circuit of the gyro-TWAs made of the BeO-SiC ceramic with certain relative permittivity and loss tangent are theoretical calculated, simulated and measured. The field distribution, dispersion and loss properties of three different dielectric loaded circular HEd12, HEd22 and TEd02 modes (corresponding to the TE11, TE21 and TE01 modes in the smooth hollow cylindrical waveguide respectively) in different frequency bands are respectively investigated. The theoretical analysis, simulation, and measurement results have a good agreement. This work has clear guiding significance for the stable work of gyro-TWAs.
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