Feasibility of a Plasma-Based Intelligent Reflective Surface

Abstract

Gaseous Plasma Antennas are devices in which an ionized gas (i.e., plasma) is exploited to transmit and receive Electro-Magnetic waves. Their main advantage over metallic systems is the possibility to reconfigure the antenna performance (e.g., radiation pattern) by electronically varying the plasma parameters (e.g., density). Recently, Intelligent Reflecting Surfaces (IRSs) have been proposed to control the environment between transmitting and receiving antennas manipulating the signals reflected. In this work, the feasibility of a plasma-based IRS is investigated. A theoretical model has been developed to assess the use of plasma as a reflecting medium. Numerical simulations have been performed to preliminary design plasma-based IRSs. Two designs of IRSs, relying on plasma properties consistent with the technology at the state-of-the-art, are proposed. The former enables beam steering operations depending on the continuous control of the phase of the reflected wave. The latter exploits a 1-Bit coding strategy to produce specific diffraction patterns. The main advantage of a plasma-based IRS with respect to the metallic counterpart is the possibility to control the phase of the reflected wave, maintaining the magnitude of the reflection coefficient close to the unit. The main drawback of plasma-based systems is the necessity of using thick plasma elements (in the order of the wavelength in the air) to control the phase of the reflected wave over 360 deg. This constraint can be relaxed if digital plasma elements are adopted.

Plasma-Based Reflective Surface for Polarization Conversion

“…At the same time, the intensity of the magnetostatic field B0 can be varied using electromagnets (e.g., by current-controlled solenoids) [30]. The collision frequency ν is associated with Ohmic losses occurring within the plasma [24] that are proportional to n0. With this regard, it is worth introducing the neutral gas pressure p0, which represents an auxiliary parameter more often used to characterise plasma discharges rather than n0…”

“…and the resonance frequency occurs at For what follows, it is more practical to define the propagation intervals in terms of the corresponding plasma density values ne rather than the operation frequency ω [24]. Specifically, the critical densities n p e , n R e , n L e , n 0 e identify the values of ne for which ω is equal to ωp, ωR, ωL, and ω0, respectively.…”

“…1. A homogeneous plasma slab of thickness z pl is located on top of an infinite Perfect Electric Conductor (PEC), constituting the ground plane [24]. A uniform magnetostatic field B0 is assumed to be aligned with the z-axis of the reference frame depicted in Fig.…”

“…where Ei is the complex electric field vector associated with the incident wave, Er corresponds to the reflected wave, and Γ is the reflection coefficient [24]. As done above, the superscripts refer to mode + and mode -, respectively.…”

“…Theoretical investigations proved that, by varying the plasma properties (e.g., density), it is possible to selectively control the transmission through a magnetized plasma layer of right-handed or left-handed CP waves [22], as well as Transverse Electric (TE) or Transverse Magnetic (TM) waves [23]. At the same time, EM signals can be controlled by relying on plasmabased reflective surfaces [24], [25]. In these devices, the unit cells consist of plasma elements placed on top of a ground plane.…”