Design of a Hybrid Metal-Plasma Transmit-Array With Beam-Scanning Capabilities

This article presents the complete design of a hybrid metal-plasma transmit-array antenna with beam-scanning capabilities. The antenna operates at 1.07 GHz and consists of an active metallic dipole, a metallic ground plane (GP), and a set of cylindrical plasma discharges arranged in a 2-D lattice. The main lobe of the antenna can be tilted toward different directions simply by turning on/off specific subsets of plasma discharges. Toward this aim, a two-step optimization strategy based on the combination of a particle swarm optimization (PSO) and of a genetic algorithm (GA) is adopted. A realistic model of the antenna has been simulated in CST Microwave Studio. To derive plasma parameters, a prototype plasma discharge has been realized and tested. Each plasma bar included in the numerical setup comprises not only the plasma material, but also the glass envelope and the metallic electrodes used to confine and generate the plasma, respectively. An analysis has been carried out to evaluate the effects of adding the electrically long metallic cables to each discharge needed to ignite and sustain the plasma. The radiation properties of the array can be maintained thanks to the insertion of inductances between the electrodes and the cables. Finally, a sensitivity analysis has been conducted to identify intervals of plasma density and neutral gas pressure within which the beam-scanning capabilities of the antenna remain unaffected.