Radiation of twisted waves from a phased array of loop antennas in a resonant magnetoplasma

Abstract

A study is made of the radiation from a phased array of circular loop antennas in a resonant magnetoplasma. The loops are assumed to have a finite radius and be located on a circumference in such a manner that their axes are aligned with a static magnetic field superimposed on the plasma. The emphasis is placed on determining the total radiated power of such an array and the partial powers going to different azimuthal field harmonics. For these quantities, rigorous integral representations are obtained using an expansion of the excited field in terms of cylindrical vector eigenfunctions of a magnetized plasma medium. Numerical results are reported for the radiation characteristics of the phased array in the whistler frequency range under conditions of the Earth's ionosphere. It is shown that an appropriately phased array is capable of selectively exciting waves with the desired helicity of the phase front and can be useful as a source of twisted whistler-mode waves in a magnetoplasma.