Mutual Coupling Effect on Arbitrarily Oriented VLF Circular Antenna Array in Ionospheric Plasma

Mutual coupling between the space-borne antenna has an essential impact on the communication characteristics of a wireless link to submerged submarines. In this article, the mutual coupling between antennas of a circular array in an anisotropic plasma over a very low-frequency (VLF: 3–30 kHz) range is investigated. An expansion of the currents into phase modes enables us to develop an efficient method to analyze the mutual coupling between antennas. The $N$ -coupled integral equations for antennas of an array are first derived with full consideration of the mutual coupling effect. By making use of the phase modes combined with the method of moment (MoM), the $N$ -coupled integral equations are decomposed into independent ones and solved for each phase mode. Computations and discussions show that the self and mutual impedances of antennas are increased with the geomagnetic field tilt angle. Moreover, the mutual impedance is decreased with the increasing electrical separation, thereby indicating that the mutual coupling effect is weakened as the separation increases. The accuracy of the proposed method is verified by comparing the computed results with experiments and simulation using commercial electromagnetics software FEKO.