Experimental and Numerical Studies of a Tunable Plasma Antenna Sustained by RF Power

In this work, a custom plasma antenna was created, in which the pressure and gas composition could be varied. The reflection coefficient, deposited power, and the antenna transmission and reception gains were measured for an argon plasma at 0.3 torr sustained by radio frequency power up to 150 W at an excitation frequency of 98 MHz. These measurements were performed through a single RF connector with the help of a directional coupler circuit that isolated the high-power excitation signal from the low-power probing ones. It was found that the resonant frequency of this plasma antenna could be tuned over a span of 80 MHz by varying the applied power in the range of 10-150 W. The antenna gain could also be varied with applied power. At power levels exceeding 40 W, the gain approached, within 3 dB, that of a standard reference antenna. The experimental setup was modeled using ANSYS HFSS software. The simulation and experimental results were found to be in good agreement. This study shows the viability of creating tunable plasma antennas with gain comparable to that of metallic antennas.