Using Loop-Gap Resonators to Characterize the Permeability of Metamaterials at Microwave Frequencies Cornell, Ava H.
A negative-index material (NIM), a metamaterial with simultaneously negative effective permittivity and permeability, was composed from periodic arrays of split-ring resonators (SRRs) and aluminum cut wires. The NIM was loaded into the bore of a loop-gap res- onator (LGR) and reflection coefficient measurements were used to characterize its perme- ability. Unexpectedly, many numerical simulations and experimental measurements have suggested that the imaginary component of the cut wire permeability can be negative which implies power generation rather than dissipation. In this project, the reflection coefficient measurements were fit to a model proposed by Pendry and coworkers and used to determine the resonant frequency, magnetic plasma frequency, and damping constant of the metamaterial’s effective permeability. By comparing these parameters with those found for arrays of exclusively SRRs, the presence of cut wires was shown to have almost no effect on the permeability of the NIM when in the presence of a pure magnetic field. In future research, similar analysis could be done for measurements taken when an external source is used to establish a current in the cut wires.
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