A small dielectric-loaded slot antenna fed by a finite-width substrate microstrip

Abstract

A resonant slot antenna requires a size of about a half-wavelength long. This places a great restriction on its usage in the low frequency end because the size will be too large. Attempts have been made on using dielectric materials to reduce the slot size required for an effective radiation. In this paper, we suggest a small slot antenna loaded by a dielectric hemisphere and with a novel feeding structure — a finite-width substrate microstrip. The feeding microstrip is to be laid on top of a finite-width dielectric strip which is then firmly mounted onto the ground plane. The slot can be simply cut on the ground plane and be covered by the dielectric hemisphere. In our contemplation, the finite-width dielectric substrate can be made as a stand-alone component which can be attached to any metallic surface, e.g., the case of a mobile phone or an electronic appliance, and on such a surface a slot can be cut through to complete an antenna. Reduction in size of the slot is mainly achieved by the dielectric hemisphere, which is to be composed of several dielectric layers with a gradual change in the dielectric constant. As manufacturing of dielectric hemispheres with different dielectric layers is still not quite realizable at the present moment, the antenna is primarily analysed theoretically.