Electric dipole radiation through a finite conical plasma sheath

The ionized boundary layer that forms around a reentry vehicle is represented by a conical sheath having a surface impedance which is determined by the integrated electron density in the boundary layer. This cone can support surface currents that are induced in it by a Hertzian dipole antenna situated on its axis. The radiation pattern of such a structure at wavelengths short compared to the slant height is calculated by a perturbation technique. The calculation holds when the surface conductivity of the sheath varies linearly with distance from the apex of the cone. Plots are presented showing the effects of sheath strength, slant height, and antenna frequency on the patterns.