Circular TE0n Mode Filters for Guided Millimeter-Wave Transmission

A millimeter-wave circular TE₀₁ mode waveguide generates undesired circularly symmetric modes (TE₀₂, TE₀₃ modes, etc.) in bends or at discontinuities along a waveguide line. This paper describes the theory and experiment on the TE₀₂ and TE₀₃ mode filters developed for guided millimeter-wave transmission. The experimental results of two improved TE₀₃ mode filters show that the attenuation of the TE₀₃ mode is more than 16 dB for one type over the 40-70-GHz range. The TE₀₁-mode insertion loss of another type is about 0.2 dB over the 40-80-GHz range. The present mode filters can be applied to various high-speed guided rnillimeter-wave systems currently under development.