RADIATION FROM AN ANNULAR SLOT ANTENNA SYMMETRICALLY COVERED BY A DIELECTRIC CYLINDER OF FINITE HEIGHT

In this paper, the radiation properties of an annular slot antenna of infinitesimal aperture and radius a, cut in an infinite ground plane a nd covered by a dielectric cylinder of finite height, are investigated analytically. The excitation is assumed to be a circumferentially con stant voltage at the slot opposite edges. The unknown electromagnetic field is expressed using the mixed mode spectrum of a radial dielectri c waveguide. Then, by enforcing the satisfaction of the appropriate bo undary conditions, an integral equation is derived in terms of the unk nown electric field distribution E(z). This equation is solved by empl oying Galerkin's technique and the electromagnetic field distributions are computed in all the regions of the 3-D space. Finally, based on t hese results, the input impedance and the far field pattern of the ant enna are obtained. Numerical results are presented for several cases.