Theory of a VLF Strip Antenna Located in an Anisotropic Plasma

Abstract

For spaceborne transmitting systems, strip antennas provide a new scheme in boosting the radiation efficiency due to their availability in generating larger current moments. In this article, we investigate the theory of a very-low-frequency (VLF: 3–30 kHz) strip antenna immersed in a homogeneous anisotropic plasma. The focus lies on the analytical method for calculating the current distribution and input impedance of the antenna, where the current distribution, in this case, consists of two parts of distribution in both longitudinal and transverse directions. Kernel function for a strip antenna at arbitrary orientations is derived with the help of coordinate transformation, and the current integral equation is solved via the method of moments (MoM). Computations show that the surface currents on a strip antenna will concentrate near the edges of the strip, and the input impedance of the antenna will increase with either the length-to-width ratio or the dip angle. Simulation results using commercial software FEKO exhibit good consistency with the computed results, thus verifying the accuracy of the proposed method. By comparison of the input impedances with linear antennas, it is found that strip antennas are more efficient than linear antennas when the length-to-width ratio is selected properly.