Antenna miniaturization: definitions, concepts, and a review with emphasis on metamaterials

The ability to shrink the physical dimensions of an antenna without significant performance degradation has been of great interest for over half a century. Over the decades, several antenna miniaturization techniques have been proposed, from structural modifications and lumped component loading, to the use of high permittivity/permeability materials, to the more recent applications of metamaterials. In this paper, we provide an overview of antenna miniaturization and a review of various miniaturization techniques with an emphasis on metamaterials. We choose to restrict the scope of our review primarily to antennas for which prototypes have been built and their properties measured. In particular, we concentrate on those metamaterial techniques categorized into the following groups: composite right/left-handed metamaterials, high impedance surfaces, and metamaterial-inspired techniques. Finally, we provide a summary table that allows the reader to compare the performance trade-offs between various miniaturized antennas.