Radiation From a Multiple Dipole Antenna With Phased Excitation in a Magnetoplasma

Radiation characteristics of a multiple dipole antenna immersed in a cold homogeneous magnetoplasma are considered. The antenna consists of phased electric dipoles which have a common geometric center and make a certain angle to one another. Each dipole is perpendicular to an external static magnetic field and assumed to be electrically short, so that the current of each has a triangular distribution. Closed-form expressions are obtained for the total radiation resistance of such an antenna and its partial radiation resistances which describe the excitation efficiency of different azimuthal harmonics of the radiated field. It is found that the antenna with appropriately phased currents in the dipoles is capable of selectively exciting twisted electromagnetic waves with given azimuthal indices in a magnetoplasma such as exists in the Earth’s ionosphere.