Metamaterial-inspired engineering of antenna systems

Summary form only given. A number of advances in the use of metamaterials and metamaterial-inspired structures to improve the overall efficiency and bandwidth performance of electrically small antennas (ESAs) in the VHF, UHF and microwave regimes will be reviewed. Metamaterials have led to a different paradigm for achieving electrically small radiating and scattering systems. Many of our initial electric and magnetic metamaterial-based ESA designs have been realized through the introduction of the corresponding metamaterial-inspired near-field resonant parasitic element antennas. Their further miniaturization at VHF and UHF frequencies has been enabled by introducing lumped elements as was done to achieve the highly subwavelength ENG, MNG, and DNG unit cells reported. Many of these metamaterial-inspired ESA designs have now been fabricated and tested. The measurement results are in very nice agreement with their predicted behaviors. These results will be presented and discussed. While these initial efforts emphasized high overall efficiencies without using any external matching networks, more recent resonant near-field parasitic designs have also explored how close their Q values can come to the Chu limit. Several of these ESA designs, their frequency bandwidths, and their associated Q values will be compared to various reported limits. It will also be shown that the corresponding active metamaterial element versions of these metamaterial-inspired ESA designs, i.e., replacing the internal passive elements in successful narrow bandwidth, high overall efficiency designs with active elements, could potentially have very large instantaneous bandwidths while maintaining their overall efficiencies even when they are very electrically small. Related active coated nano-sized particle designs at optical frequencies have led to highly sub-wavelength lasing systems and their proposed nano-sensor and nano-antenna applications.