Exploration of advantages and drawbacks of metamaterial leaky-wave antennas

Very recently, the development of highly-directive antennas for broadside radiation has attracted the interest of many researchers, and several structures have been proposed and realized. With respect to other highly-directive structures, planar leaky-wave antennas (LWAs) have the typical advantages of being simple, low-cost, and compatible with planar integration. Conventional planar LWAs may be built in several ways, with dielectric and/or metallic layers. Most of these structures may be viewed as a grounded dielectric slab covered with a “partially reflecting surface” (PRS). A simple source is used to launch a cylindrically propagating set of TM and TE leaky waves. The source can be a horizontal infinitesimal electric or magnetic dipole (representing a finite printed dipole or a narrow slot on the ground plane, respectively), although the radiated pattern and the high-directivity effect mainly depend on the structure and not on the particular source. Although not immediately recognized, recently proposed one-dimensional electromagnetic bandgap structures also fall into this class of antennas. The recent tremendous interest and research in metamaterials has led to the development of high-directivity antennas using a metamaterial layer (for instance, a grounded layer with a relative permittivity near zero). It can be shown that also such novel antennas are intrinsically LWAs, and hence a comparison with conventional LWAs (in terms of various quantities of interest, such as directivity, bandwidth, power enhancement, efficiency, and physical size) is warranted. In this work, the properties of such metamaterial LWAs will be explored, and comparisons will be made with conventional PRS-based LWAs. It will be shown whether and how the possible use of artificial metamaterial layers may improve the performance of typical LWAs, especially in terms of bandwidth and efficiency.