Feasibility Study on a plasma based reflective surface for SatCom systems

Gaseous Plasma Antennas (GPAs) can be defined as devices that exploit weakly or fully ionised gas to transmit and receive electromagnetic waves. GPAs can offer several advantages over metal antennas: while in use, they are (i) electronically reconfigurable with respect to electromagnetic response (e.g., gain, frequency of operation) and (ii) transparent to incoming electromagnetic waves whose frequency is greater than the plasma frequency. When not in use, the plasma can be turned "off", and the GPA reverts to a dielectric tube with a very low radar cross-section. Thus, a GPA can reduce co-site interferences. The reduced interferences make GPAs suitable to be stacked into arrays and surfaces that can steer the beam electronically by tuning the plasma parameters. Reconfigurability and beam-steering capabilities make GPAs very appealing for Satellite Communications (SatCom). The reduced co-site interferences allow GPAs to be stacked in each other's proximity on the same satellite, reducing the mass and volume budget for the telecommunication subsystem. Moreover, the antenna pointing, and tracking obtained by steering the beam electronically, rather than varying the orbital attitude of the satellite, can be an enabling factor for several space missions. In this framework, a plasma-based Intelligent Reflective Surface (IRS) has been recently proposed to maximize reconfigurability and beam-steering capabilities. IRS are engineered, programmable planar structures capable of controlling the scattering and reflection of radio signals by tuning the EM properties of the surface to obtain beam-steering and beam-forming electrically. In this work, we present the first step toward the practical implementation of an IRS in C-band capable of electrically, rather than mechanically, tuning its beam steering and focusing capabilities. The study here presented combines numerical and experimental approaches. First, a target plasma discharge has been characterized experimentally to provide the plasma parameters to estimate the EM response using numerical simulations. The numerical simulations considered a simplified single-element plasma cylinder in this first stage. Then, the glass envelope needed to contain the plasma was added to the column, and its impact on the performances was evaluated. Finally, a finite surface of 10 plasma cylinders (with glass) has been considered. The preliminary results prove the capability to obtain beam-steering by tuning the plasma density within the discharges.