Matched impedance thin composite magneto-dielectric metasurfaces

Abstract

The advantages and disadvantages of dielectric loading applied to electromagnetic devices such as antennas using high permittivity materials is well known. Sometimes overlooked, however, is the same effect using a material with magnetic properties. This is mainly due to the fact that most natural magnetic materials exhibit large losses that make them virtually unusable at high frequencies. If materials that exhibit magnetic and dielectric properties with reasonable losses were available then more advanced RF devices and antenna systems could be created. For instance, the use of these materials in conjunction with antennas would facilitate the development of designs with much smaller physical footprints than are typically possible, with few performance compromises [1]. Recently, composite magneto-dielectric substitutes, called metaferrites [2], have been engineered as a possible way to address this need for magnetic materials that are usable beyond 1 GHz. In [2], Kern et al. demonstrated that the properties of a PEC backed slab of magnetic material with frequency dependent permeability could effectively be achieved using a high impedance electromagnetic bandgap (EBG) structure. It was also shown that the real and imaginary parts of the effective permeability of an equivalent magnetic material slab could be related to the values of the surface impedance for the EBG structure. In this paper a new design technique for creating matched magnetodielectric metamaterial slabs is introduced. The technique is based on using a genetic algorithm (GA) to optimize [3,4] thin metallo-dielectric metasurfaces comprised of a periodic array of electrically small unit cells and backed by a perfectly conducting ground plane. Examples will be presented to demonstrate the effectiveness of this technique.