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Several lumped element-based epsilon-negative (ENG), mu-negative (MNG), and double-negative (DNG) metamaterial designs have been developed for operation at 400 MHz in the UHF frequency band. The use of lumped elements enabled the creation of highly sub-wavelength unit cells whose overall size was λ0/d∼75 at 400 MHz. The measured negative index material (NIM) showed an effective real index of refraction nreal=-3.11 with a total loss that was less than 1 dB/cm. The NIM bandwidth was >10% in the neighborhood of 400 MHz. [ABSTRACT FROM AUTHOR]

Using numerical simulation techniques, the transmission and reflection coefficients, or S parameters, for left-handed metamaterials are calculated. Metamaterials consist of a lattice of conducting, nonmagnetic elements that can be described by an effective magnetic permeability μ[sub eff] and an effective electrical permittivity &Vegr;[sub eff], both of which can exhibit values not found in naturally occurring materials. Because the electromagnetic fields in conducting metamaterials can be localized to regions much smaller than the incident wavelength, it can be difficult to perform accurate numerical simulations. The metamaterials simulated here, for example, are based on arrays of split ring resonators (SRRs), which produce enhanced and highly localized electric fields within the gaps of the elements in response to applied time dependent fields. To obtain greater numerical accuracy we utilize the newly developed commercially available code MICROWAVE STUDIO, which is based on the finite integration technique with the perfect boundary approximation. The simulation results are in agreement with published experimental results for the frequencies and bandwidths of the propagation and stop bands associated with the various structures. We further analyze the properties of an individual SRR, and find the dependence of the resonant frequency on the SRR radius, ring thickness, inner/outer radial gap, azimuthal gap, electrical permittivity, and magnetic permeability of the components’ materials. Comparison with previously published analytical estimates shows only approximate agreement with the simulation results. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We report a fabrication approach for making nanometer wide gaps between two planar metallic electrodes, which can be utilized for the formation of thermo-tunneling devices. The technique is a three dimensional variant of the electromigration techniques used for creating nanometer sized gaps on planar surfaces. The gap is formed by applying a low level voltage between two parallel electrodes, each deposited on separate wafers that have been bonded together. I-V and thermal characterization of the gap show very good agreement with modeling results, indicating a tunneling gap on the order of 0.5-1 nm. [ABSTRACT FROM AUTHOR]

A lumped element-based negative index metamaterial (NIM) was designed, fabricated, and tested for operation at 400 MHz in the ultrahigh frequency (UHF) band. At 400 MHz the measured real part of the index of refraction of this NIM was nreal=-3.11 with a loss that was less than 1 dB/cm using unit cells whose overall size d was λ/d∼75. The NIM bandwidth was >10% in the neighborhood of 400 MHz. [ABSTRACT FROM AUTHOR]

A gradient index (GRIN) lens using a negative index of refraction material (NIM) has been designed and tested. The GRIN lens was fabricated using a NIM slab with a variable index of refraction perpendicular to the propagation direction. Ray tracing calculations based on the isotropic Eikonal equation determined the index of refraction gradient required for a given focal length. An electromagnetic code was then used to design the required ring and wire unit cells. Finally, the index of refraction was approximated using ten discrete steps in an effective medium simulation for the GRIN lens that agreed with the experimental measurements. [ABSTRACT FROM AUTHOR]

We used a broadband, free-space, focused-beam system to measure the transmission and reflection in left-handed-material (LHM) slabs. The samples were made of alternating patterns of copper wires and split-ring resonators on Rogers 5880 substrates separated by Rohacell™ spacers. The measured data show very good agreement with numerical simulations. The measured insertion loss of this structure was -1.1 dB/cm at the LHM pass band. Simulations suggest that the loss may be attributable to the finite conductivity of the copper patterns. [ABSTRACT FROM AUTHOR]

Negative index of refraction materials have been postulated for many years but have only recently been realized in practice. In the microwave region these materials are constructed of rings and wires deposited on a dielectric substrate to form a unit cell. We have constructed, experimentally characterized, and simulated several of these structures operating in the 10-16 GHz range. The origin of the dissipative losses has been identified and effective schemes to reduce them devised and implemented. Numerical simulation and experimental verification shows that losses in negative index of refraction materials can be significantly reduced by minimizing the underlying losses of the constituent materials. [ABSTRACT FROM AUTHOR]