Feasibility study of a novel class of plasma antennas for SatCom navigation systems

摘要

Gaseous Plasma Antennas (GPAs) are devices that exploit weakly or fully ionized gases to transmit and receive electromagnetic (EM) waves. GPAs can offer several advantages over their metallic counterparts since radiation pattern, gain and operating frequency depend on the electrical response of the plasma. A particularly appealing field in which these antennas could be exploited is the Global Navigation Satellite System (GNSS). In fact, GPAs allow to meet the increasingly strict requirements imposed on the GNSS application; specifically, they can drastically reduce multipath errors. This feature is particularly important for the future use of GNSS in critical networks, as for example Public Protection and Disaster Relief (PPDR). In order to verify whether GPAs can be realistically exploited on this field, a preliminary analysis has been accomplished to assess their performances in the L band (i.e., the frequency range proper of GNSS operations). Specifically, two circularly polarized antennas, conceived as the basic elements of an array of GPAs, have been compared. The two concepts, namely a curl and a turnstile antenna, have been characterized in terms of reflection coefficient, axial ratio, and maximum gain. A combined numerical and experimental approach has been adopted for this analysis. Dedicated plasma sources have been manufactured in-house to obtain a realistic evaluation of the plasma parameters. Specifically, the plasma density and the background neutral pressure have been measured with a Pirani gauge and a microwave interferometer, respectively. Once these parameters are known, and in turn the electrical response of the plasma has been assessed, the characteristics of the two antennas have been numerically calculated by means of the commercial software CST Microwave Studio (R). The curl antenna concept results the most promising one provided that it satisfies the functional requirements imposed by GNSS application (i.e., circular polarization in the L-frequency band).