Analysis and Experimental Validation of Plasma-Based Reflecting Surfaces

An experimental and numerical investigation of plasma-based reflecting structures operating in the X-band is presented. The structures consist of cylindrical plasma discharges placed in front of a metallic ground plane and illuminated by a horn antenna. Microwave interferometry is first used to characterise the discharges and determine the electron density employed in the full-wave numerical model of a two-discharge prototype. Outdoor radiation-pattern measurements at 8.2 GHz show that plasma ignition increases the broadside gain by 1.70 dB and attenuates the adjacent lateral response. CST simulations reproduce the same overall trend, although stronger lateral attenuation is predicted. The numerical analysis is then extended to a ten-discharge configuration for beam splitting at 8 GHz, accounting for the glass vessels, electrodes and polytetrafluoroethylene (PTFE) support. Configurations with and without the support are compared to assess its electromagnetic influence. With the centred PTFE support, two main lobes are obtained near ±40°. The support preserves the beam-splitting behaviour while reducing the peak realised gain and increasing the central response, despite the small additional dissipative losses. Sensitivity analyses of the plasma densities and glass permittivity show that the forward beam directions remain nearly unchanged over the tested ranges, while central-lobe suppression varies. The results provide experimental evidence of radiation-pattern reconfiguration in the two-discharge prototype and a numerical basis for investigating beam splitting in the complete structure. They also show that the mechanical support must be included when predicting the electromagnetic response of the reflecting surface.