engleski

Is it Feasible to be Invisible? From Plasma to Active Dispersionless Plasma-like

The feasibility of practical implementations of electromagnetic cloaking technology (the ‘invisibility technology’) proposed in the recent literature will be analyzed. It will be shown that one of the basic problems present in all current proposals is a narrowband operation caused by basic dispersion constraints of any passive medium. However, the use of active transmission-line-based metamaterials, for which the basic constrains do not apply, may overcome this problem. The basic properties of these active materials (dispersion and stability) were investigated with the help of commercial circuit simulator. Simulation results showed that is possible to achieve either electric or magnetic ‘plasmonic’ behavior in a wide frequency band (limited by the characteristics of active negative converters). The experimental prototype of basic active ‘plasmonic’ transmission line operating in RF regime , developed at University of Zagreb, will be presented. It will be shown that the measured results indeed reveal almost dispersionless equivalent permittivity within a frequency band of one octave. It will be shown that these structures support superluminal phase velocity and group velocity, but they are perfectly compatible with general causality and relativity. In addition, the use of prototyped active ‘plasmonic’ transmission lines for 2 D cloaking will be presented. The 2D model of plasmonic cloak comprising 2D active transmission lines was analyzed using a standard circuit simulator. The plane wave excitation was simulated as an array of voltage sources in the circuit simulator and distribution of the voltages in the nodes of 2D active line (that corresponds to the distribution of the E field) was plotted. As expected, the results showed cloaking within a wide frequency band.

active metamaterial; plasma

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