Composite defect-mode superstructures and wideband EBG resonator Antennas

We propose two electromagnetic band gap (EBG) structures made out of multi-layer dielectric slabs to enhance the bandwidth of EBG resonator Antennas (ERAs). These multi-layer structures are designed to achieve wide defect-mode bandwidths. Wide defect modes are created by optimising the permittivity and thickness of the individual slabs, as well as the inter-slab separations. Using these EBG structures as ERA superstructures and truncating them to an appropriate area, two ERAs were designed. They exhibit pattern bandwidths nearly twice as wide as the classical ERAs. 3dB directivity bandwidths of 14.1% and 19.3% with a maximum directivity of 17.5 dBi and 18.7 dBi, respectively, were measured for the two ERA prototypes. The lateral dimensions of the ERA superstrates are 1.5×1.5λ₀² which represent more than 90% reduction in superstrate area when compared with classical ERAs. Small size and simple configuration make these ERAs very suitable for high-gain millimetre wave applications when they are scaled to those bands.