A novel design technique for ultra-thin tunable EBG AMC surfaces

A design methodology is presented for achieving considerable operating bandwidth at low frequencies, specifically below 1 GHz, by the use of an ultra-thin tunable electromagnetic bandgap (EBG) artificial magnetic conducting (AMC) surface. By incorporating a high dielectric, ultra-thin substrate into the design of an EBG AMC surface, it is not possible to achieve a large instantaneous bandwidth of operation. However, by utilizing a tunable surface, the narrow bandwidth resulting from the ultra-thin high-k design can be exploited and used advantageously. The narrow bandwidth of the structure gives rise to a "channel" frequency determined by the sharp resonance of the AMC surface. By actively tuning the dielectric substrate and hence the overall capacitance of the surface, this resonant frequency can be shifted between channels to cover a reasonably wide bandwidth. Thus, the same bandwidth can be utilized as that of a much thicker structure by tuning the thinner AMC accordingly. This design approach is especially useful at low frequencies below 1 GHz, where the overall thickness of conventional AMC surfaces becomes an issue of practical limitation. Several design examples are presented for ultra-thin tunable EBG AMC surfaces that have an overall thickness on the order of λ/2000.