Analysis of dielectric-loaded annular slot array antenna

A method is established for the analysis of annular slot array antennas loaded with dielectric layers and fed by either radial waveguide or cavity. The analysis is based on the boundary value method. The Greens functions for each region are obtained, and then the induced magnetic current over the slots is expanded into Fourier series with unknown coefficients. Boundary conditions are applied, and a matrix equation for these unknown coefficients is obtained. For narrow slots the number of unknowns equals the number of annular slots, and an extremely rapid solution is obtained. The far-field formulation is derived using the magnetic current on the dielectric layer. The method is confirmed numerically by comparing the simulation results for sample small antennas with a commercial numerical tool (IE3D), and good agreement is achieved. It is shown that adding the dielectric layers can improve the antenna directivity. In comparison with other methods, the proposed method is very efficient, and its computation efforts depend on the number of annular slots and not the size of the antenna. As an example, for a single-slot antenna the number of unknowns to be determined is only one, while in IE3D it is more than 300.