Radiation characteristics of input power from surface wave sustained plasma antenna

Abstract

This paper reports radiation characteristics of input power from a surface wave sustained plasma antenna investigated theoretically and experimentally, especially focusing on the power consumption balance between the plasma generation and the radiation. The plasma antenna is a dielectric tube filled with argon and small amount of mercury, and the structure is a basic quarter wavelength monopole antenna at 2.45 GHz. Microwave power at 2.45 GHz is supplied to the plasma antenna. The input power is partially consumed to sustain the plasma, and the remaining part is radiated as a signal. The relationship between the antenna gain and the input power is obtained by an analytical derivation and numerical simulations. As a result, the antenna gain is kept at low values, and most of the input power is consumed to increase the plasma volume until the tube is filled with the plasma whose electron density is higher than the critical electron density required for sustaining the surface wave. On the other hand, the input power is consumed to increase the electron density after the tube is fully filled with the plasma, and the antenna gain increases with increasing the electron density. The dependence of the antenna gain on the electron density is the same as that of a plasma antenna sustained by a DC glow discharge. These results are confirmed by experimental results of the antenna gain and radiation patterns. The antenna gain of the plasma is a few dB smaller than that of the identical metal antenna. The antenna gain of the plasma antenna is sufficient for the wireless communication, although it is difficult to substitute the plasma antenna for metal antennas completely. The plasma antenna is suitable for applications having high affinity with the plasma characteristics such as low interference and dynamic controllability.

Plasma-Based Reflective Surface for Polarization Conversion

“…Namely, the radar cross-section of a GPA can be drastically reduced if the electric power to sustain the plasma is turned off and, thus, the main conductive medium fades [3]. This feature is appealing to minimize the mutual interference between several GPAs stacked into an array [4] or if stealth is required [5]. Second, the plasma properties that drive the antenna performance (e.g., density) can be controlled by varying the electric power coupled to the plasma [6], [7].…”

Feasibility of a Plasma-Based Intelligent Reflective Surface

“…First, the plasma is produced by energizing a neutral gas confined inside a dedicated vessel. Namely, when a GPA is off, it is characterized by a reduced Radar Cross Section (RCS) given the absence of the main conductive medium (i.e., plasma) [3]. This feature reduces the mutual interference between antennas stacked into arrays [4].…”

Experimental characteristics of 2.45 GHz microwave reconfigurable plasma antennas

“…Boltzmann's equation is utilized in an explicit way similar to the FDTD method. Functions ( 4) and ( 5) are utilized to calculate the electron velocity distribution [37].…”

“…where f 0 and f 1 are the isotropic and anisotropic terms of the function, respectively; v e is the electron velocity; and C 1 , C 2 and C 3 are the terms for the elastic neutralization, ionization, and inelastic excitation collisions, respectively [37]. Electrons are trapped by the oscillating EM field at the frequency of 2.45 GHz.…”

“…Electrons are trapped by the oscillating EM field at the frequency of 2.45 GHz. The electron spatial distribution can be obtained by function (6) as follows [22,37]:…”