Authors: Dr. Mohsen Kavehrad
Source: FERMAT, Volume 7, Article 4, Jan-Feb., 2015
Abstract: Demands by the communications industry for greater bandwidth push the capability of conventional wireless technology. Part of the Radio Spectrum that is suitable for mobility is very limited. Higher frequency waves above 30 GHz tend to travel only a few miles or less and generally do not penetrate solid materials very well. Unmanned Aerial System applications require electronic scanning antenna capabilities, in challenging environmental conditions, over very large bandwidths. In addition to that, it is desirable to have as much reduction as possible in size, weight, power and cost. Metamaterials are recently being introduced by periodic repetition of some inclusions in a host medium, which may be described as effective media characterized by a set of equivalent constitutive parameters. Self-similarity in creating periodic structures is the basis of building volume or 2D holographic components. The latter does more than periodic repeats. Similar, but more advanced concepts (fractal in nature) are used to model phase screens used in modeling the atmospheric turbulence. Unfortunately, metamaterials (MTMs) are anisotropic (direction-dependent) and this makes their application limited in terms of use as antennas for mobile platforms. However, conceptually, controlled-anisotropy can be applied to make phased-arrays, beam-forming, and beam scanning. This issue then begs the question of cost comparison with conventional materials that can be found in nature, e.g., low-cost optics lenses, or conventional RF scanning antennas. As for lensing and fixed platform imaging, the story is very different, as super-lens is expected to be a byproduct. Nevertheless, even if metamaterials become readily available, the atmosphere around the globe cannot be replaced. Neither, broadband wireless connectivity to a mobile can be achieved via fiber optics. This paper, presents a Hybrid radio-frequency (RF) and Wireless Optical solution to provide adaptive sensing in an opportunistic fashion, with or without metamaterials. A byproduct of the latter will be broadband and reliable global connectivity.
Index Terms: Multiband, Multiservice, Sensing: Metamaterials Myth and Reality
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Multiband, Multiservice, Sensing: Metamaterials Myth and Reality