Broadband, Volumetric Negative-Refractive-Index Media
نویسندگان
چکیده
Broadband, Volumetric Negative-Refractive-Index Media by Scott M. Rudolph Chair: Anthony Grbic Since their invention, negative-refractive-index (NRI) media have been plagued by three primary limitations: narrow bandwidth, high loss and polarization dependence. In this thesis, each of these problems is addressed. First, a new metamaterial topology that achieves negative permeability over a broad bandwidth is introduced. This structure is used to realize a broadband, volumetric NRI medium that is then thoroughly analyzed using multiconductor transmission line (MTL) theory. A homogenized, periodic form of MTL analysis is used to derive a simplified dispersion equation, as well as expressions for the Bloch impedance, permittivity and permeability for an infinite NRI medium. The analytical methods are supported by both full-wave simulation and measured results. Two broadband NRI lenses are presented: one contained inside a waveguide and the other in free space. Both lenses exhibit super-resolving capabilities: the first at 2.45GHz and the second at 10.435GHz. The transmission and reflection coefficients of the free-space lens are measured using a quasioptical Gaussian beam telescope, and the material parameters of the lens are extracted for these measurements. This lens exhibits a negative index of refraction over a fractional bandwidth of 41.2%. The
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