Suppression of substrate coupling between slot antennas using electromagnetic bandgap structures

In this paper, the effect of finite substrate thickness is investigated for a single slot antenna printed on a grounded dielectric. It is concluded that a thin dielectric backed by a conductor wall drastically degrades the performance of the slot antenna while an EBG reflector provides unidirectional radiation pattern and gain improvement and increases the efficiency of the antenna by suppressing the unwanted parallel-plate waveguide mode. The EBG reflector is a mushroom type structure designed to induce a stopband around the resonance frequency of the slot antenna, i.e. at 5.2 GHz. It is also used as the reflector in a two slot antenna system. Fullwave simulations demonstrate that the designed EBG reflector results in improvement of antenna isolation by more than 20 dB across the frequency range of 3.05 GHz to 5.35 GHz by suppressing the substrate coupling through parallel-plate waveguide mode.