Feasibility study on a plasma based reflective surface for SatCom systems

Abstract

Gaseous Plasma Antennas (GPAs) exploit an ionized gas to transmit and receive electromagnetic waves. GPAs offer several advantages over metal antennas since, while in use, they are electronically reconfigurable in terms of radiation pattern and operation frequency. When not used, the plasma can be turned “off”, and the GPA reverts to a dielectric tube with a very low radar cross-section. This makes GPAs suitable to be stacked into arrays, providing they can reduce co-site interference. Thus, GPAs are very appealing for Satellite Communications (SatCom). The antenna pointing and tracking obtained by steering the beam electronically, rather than using mechanically moving parts, can enable several space missions. A plasma-based reflective surface has been recently proposed in this framework to maximize reconfigurability. Such a device consists of many plasma discharges placed on top of a metallic ground plane, and the reflection of radio signals can be controlled by electronically varying the plasma properties (e.g., density). This work presents the first step toward practically implementing a plasma-based reflective surface in the X-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 needed to estimate the electromagnetic (EM) response using numerical simulations. Then, the numerical simulations were performed to preliminary design a plasma-based reflective surface. At first, a simplified single-element plasma cylinder was analysed. Then, the glass envelope needed to contain the plasma was added to the column, and its impact on the performance was evaluated. Finally, a finite surface of ten plasma cylinders (including glass vessels) has been considered. The preliminary results prove the capability to obtain beam-steering by tuning the plasma density within the discharges.