Novel artificial reactive impedance surface for miniaturized wideband planar antenna design: concept and characterization

The concept of a novel substrate for planar antennas, that can miniaturize the size and significantly enhance both the bandwidth and the radiation characteristics of a printed antenna on such substrate, is introduced. Using the exact image formulation for the fields of elementary sources above impedance surfaces, it is shown that a purely reactive impedance surface (RIS) with a specific surface reactance can minimize the interaction between the elementary source and its image (the RIS substrate). A RIS can be tuned anywhere between perfectly electric and magnetic surfaces (PEC and PMC) offering the unique property to achieve the optimal bandwidth and miniaturization factor. This artificial surface is designed utilizing two-dimensional periodic square patches printed on a metal-backed dielectric substrate. A simplified circuit model describing the physical phenomenon of the periodic surface representing the RIS is developed for simple analysis and design of the proposed artificial surface. Also an FDTD full-wave analysis in conjunction with the periodic boundary conditions and perfectly matched layer walls is applied to provide a comprehensive study and analysis of complex antennas on such surfaces. An example including a dipole antenna over an RIS substrate is studied and its performance is compared with those of the same antenna over PEC and PMC surfaces.