Conceptual design, manufacturing and investigation of dipole plasma ‎antenna with the capability of frequency variation in the VHF band

Abstract

In this article, we simulate and manufacture a dipole plasma antenna whose frequency is variable in the VHF band. The conductive medium of antenna is the plasma created by the DC discharge in a glass tube. To excite the antenna, we use a cylindrical aluminum coupler installed at the middle of the antenna. By varying values of gas pressure, input impedance of circuit and the voltage deference between two ends of the plasma medium, one can change the working area of antenna at a few hundred gigahertz frequency interval. Simulation and numerical calculations are carried out for an antenna with 78cm length and 2cm radius at 0.8 bar pressure exerted under 15KV voltage difference. At constant pressure, by using some parallel resistors in the antenna circuit, the impedance of discharge circuit is changed and consequently the plasma density is varied. For plasma frequencies and , using semi-experimental formulae, analysis shows resonances at frequencies 250MHz and 311MHz, respectively, which are in good agreement with the experimental results which take place at frequencies 217MHz and 272MHz. Additionally, simulation is accomplished for a metal antenna with corresponding geometry whose working frequency detected at 184MHz.