Experimental studies of the electromagnetic properties of metamaterials

Metamaterials are artificial composites that exhibit enhanced electromagnetic properties when compared to naturally occurring materials. These are artificial periodic structures with lattice constants much smaller (less than lambda/6) than the wavelength of the incident electromagnetic radiation. The electromagnetic properties are characterized by permeability and permittivity of the material; therefore by manipulating the microstructure geometry, it is possible to enhance the electromagnetic properties of such materials, hence opening a door to a wide variety of potential applications in the areas of microwaves and optics. Some of the metamaterial structures that are being researched widely are SRRs (split ring resonators) and Omega structures.;One of the important concepts concerning these materials is homogenization. To date, this concept was not validated for metamaterials using experimental analysis. In this thesis, the notion of metamaterials as homogeneous materials satisfying constitutive equations and exhibiting effective parameters is discussed. With this experimental validation, designing numerous microwave and optical devices with these materials would be highly realizable.;S-parameter measurements were made using the free space set up. TRL calibration was implemented to de-embed the reference planes for amplitude and phase measurements. Parameters like complex permeability and permittivity were extracted from the S-parameters by using Fresnel formulae for the reflection and transmission coefficients of a planar slab normally illuminated by a plane wave. The extracted properties were fitted with Kramer--Kronig's relations to prove the analyticity of the complex parameters. The properties extracted were used for homogenization studies. Measurements were performed for samples of varying thickness (i.e. one, two and three unit cells of the inclusions) and it was experimentally demonstrated that the samples exhibited the same material properties.;The next part of the work involves the studies of metamaterials with omega shaped inclusions, called omega media. The response of different orientations of these structures with respect to incident fields, were studied and some interesting observations were made, which could form the basis of microwave applications such as band stop filters and electromagnetic band gap structures.