Analysis of nested design of plasma antenna based on the azimuthally symmetric surface waves: UHF and SHF bands

Abstract

In this paper, a plasma antenna nested inside a plasma tube, called the nested model of the plasma antenna, as a suitable candidate to improve the conventional plasma antenna is theoretically investigated in ultra-high frequency (UHF) and super high frequency (SHF) ranges. Using the Fluid-Maxwell equations, the dispersion relations for both the nested model of plasma antenna and single plasma antenna and single plasma antenna are obtained to find their practical, vph≥0.85c, azimuthally symmetric surface modes. The numerical results for the single plasma antenna show that the number of practical modes is very limited in the UHF range, and in the SHF range, the phase velocities of the modes radiating over this range are mostly lower than the speed of light in vacuum. However, the results of the considered nested model indicate that in the UHF range, the number of practical modes greatly increases, and by optimizing the plasma tube parameters, the generated modes can extend over all this range, forming a mode line with the phase velocity very close to the speed of light. On the other hand, in the SHF range, employing the nested model leads to an additional mode line having higher phase velocity (coinciding with the light speed line under the optimum conditions) with respect to that of the single plasma antenna. Using the proposed nested model of the plasma antenna not only leads to clearly significant advances in the single plasma antenna but also is more controllable due to adding the plasma tube parameters.