Meta-materials with wideband negative permittivity and permeability

Recently, electromagnetic materials with negative permittivity and permeabi lity values (sometime called "media with negative refraction index") have b een given much attention in the literature. Negative values of the material parameters can be achieved in composite media near resonances, which impli es very dispersive properties. The material parameters are complex numbers to account for dissipation, and the real parts can be negative only in narr ow frequency bands. Here, we show that this limitation can be relaxed in co mposite materials with active inclusions. It is proven that, using small di pole and loop antennas loaded by certain simple electronic circuits as comp osite inclusions, the material behaves as an effective medium with real neg ative parameters in wide frequency bands. Similarly, thin sheets of negativ e materials can be simulated by strip or patch arrays loaded by active circ uits. (C) 2001 John Wiley & Sons, Inc.