THEORETICAL AND EXPERIMENTAL-STUDY OF A CAVITY-BACKED ANNULAR-SLOT ANTENNA

A simple and accurate analysis of an annular-slot antenna backed by an inhomogeneously filled cavity is described. The analysis is based on a magnetic-field integral equation, which is solved approximately usin g a variational formulation. The results obtained from the analysis ar e compared with experimental measurements on a 5 GHz annular-slot ante nna fabricated on a Duroid 5880 substrate. It is found that only three terms of a series expansion are needed for an accurate solution. Meas ured results for input impedance and far-field radiation patterns for an annular slot backed by different-sized cavities are presented.