Radiation from a slot antenna in an anisotropic plasma

Abstract

Radiation from a slot antenna in an anisotropic plasma with the static magnetic field in arbitrary direction has been investigated. The field distributions at the slot aperture have been derived assuming transverse electric excitation at the feed point and are found to support plane waves of both ordinary and extraordinary modes. Using the aperture fields as equivalent electric and magnetic current sheets the. fields outside the slot are derived in triple Fourier integral forms which are evaluated by residue theorem and saddle point method to obtain the radiation field. Numerical calculations of the time averaged Poynting vector were carried out for a half wavelength slot antenna and for plasma parameters corresponding to the region (a) of Clemmow- Mullali-Allis (CMA) diagram .. The radial component of the power flow vector normalized by the maximum power density for a half-wave slot in free-space is plotted to obtain the directional pattern. Plots of the directional pattern show that two strong pencil beams are radiated - one along the ground plane in a direction perpendicular to the slot axis and the other perpendicular to the plane of the slot. The radiation is dominated by the ordinary-mode power with a comparatively negligible extraodinary-mode power. With the static magnetic field in the yz-plane of an xyz-system, the inclination of the static magnetic field does not significantly influence the radiation pattern of an x-directed slot but has considerable effect for y and z-directed slots.In the latter cases. the beam maxima are also slightly tilted from the z and y-axes due to the lack of propagation symmetry in the yz-plane.