Antenna pattern distortion by an isotropic plasma slab

A quantitative laboratory experimental investigation has been conducted on the distortion of the main far-field radiation pattern of a horn antenna situated behind a layer of isotropic plasma. The power radiation pattern and phase for orthogonal components of the radiation transmitted through the plasma were investigated for various plasma properties. The experimental results were compared to theory based on the reciprocity theorem and good agreement was obtained. The major features are a gradual attenuation and distortion of the radiation pattern for plasma electron densities below the critical density and a rapid change in the radiation pattern with severe attenuation in the region of the critical electron density followed by "cut-off" at still larger electron densities. No appreciable polarization change of the energy radiated by the antenna is introduced by the plasma.