TM0m modes in transversely magnetised semiconductor-filled coaxial waveguide and parallel plates

The behaviour of the TM₀₁ mode found in the azimuthally magnetised, semiconductor-filled, coaxial waveguide and the transversely magnetised parallel-plate configuration has been rigorously analysed. Investigation of the Poynting vector shows field displacement in both guides, with annular and laminar regions of negative average power density. The radial displacement of the electromagnetic fields in the coaxial waveguide gives rise to double-value phase constants below cut-off and nonreciprocal phase behaviour. This does not occur in the parallel-plate structure owing to its symmetry. Attenuation due to electron collisions was calculated for the TM_0m modes in the parallel-plate case. This has implications for the attenuation expected on the TM_0m modes in the coaxial-waveguide case. Gallium arsenide and indium antimonide proved promising in the frequency range 50-150 GHz when cooled to 77 K. For nonreciprocal devices in MMICs it appears that low doping concentrations will be required