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Solving inhomogeneous problems by integral equation approach relies on the solution of volume integral equations (VIEs) and usually tetrahedral elements in geometrical discretization are required to match arbitrary shapes. However, tetrahedral discretization is expensive since special commercial software is required even for a very simple geometry. In this work, we propose a volume-element-free scheme...
A novel probe design form measuring complex permittivity of soils in-situ from 10 to 1000 MHz and above without taking soil samples is presented. The dielectric constant and conudctivity of soil is derived from step-frequency reflection taken inside a small (1∼2 inches) freshly bored holes. As a result, permittivity at various depths from surface with in-situ moisture content and soil texture can...
In this paper, a printed grid array antenna on a low cost packaging substrate is presented. Simulation and measurement results of the antenna return losses and radiation patterns are provided. Simulations show that the antenna is matched on the frequency band from 57 to 64GHz and has a broadside gain of over 11dB all over the band. Measurement results show that the antenna performance is shifted 2GHz...
This paper investigates the polarization rotation effect of metamaterial with a lattice of flattened spiral segments. This multilayered structure can be fabricated easily, and the simulation result shows that it can rotate the polarization effectively.
In this paper, we propose a new type of lossless metamaterial whose effective permittivity is tunable from negative to positive values. Its optical response is studied analytically and numerically. We further demonstrate that this tunable metamaterial can significantly modulate the phase of an incident pulse with negligible reflection loss, functioning as an efficient phase shifter.
In this study, the use of broadside-coupled SRR (BC-SRR) metamaterial topology is suggested for pressure, temperature, humidity and concentration sensor applications. Also, the use of V-shaped resonator topology is suggested for pressure sensor application. The feasibility of such sensors are demonstrated by numerical simulations for microwave region under magnetic excitation.
A particular UHF “miniaturized” antenna is presented in this paper. It is a kind of planar inverted F antenna (PIFA) which operates in a metal environment. The return loss of the antenna has been optimized over the ISM european frequency band (868 MHz). To reduce the size of the structure, the resonator has been folded under “itself” and a capacitive load is added in order to decrease the resonance...
Non-metallic, low-loss double-negative (DNG) metamaterials can be formed by three-dimensional (3D) arrays of two different non-metallic spheres arranged on a simple tetragonal lattice. Such DNG metamaterials have recently been found to provide DNG bandwidths of 10% through 3D arrays of two different dielectric spheres, and of 18% through 3D arrays of dielectric and magnetic spheres. However, a method...
In this paper a simple effective-media analysis (including higher-order multipoles) is used to design a single-resonator, negative-index design based on a metal-core, dielectric-shell (MCDS) unit cell. In addition to comparing the performance of the MCDS design to other core-shell negative-index designs, performance trade-offs resulting from the relative positioning of the electric and magnetic modal...
A three-dimensional (3D) lattice of nanoscale coated spheres is shown to have an isotropic negative index of refraction at optical frequencies. The nanospheres have a core of copper chloride (CuCl) and are coated by a layer of silver. The extended Maxwell Garnett model, relating the Mie resonances of the constituent spheres to the bulk response of the composite, is used for the design. The results...
Three approaches to numerical evaluation of two-dimensional Green's function under TMz polarization are studied for the Veselago Lens of finite and infinite extent. The first approach formulates the Green's function of the infinite lens in terms of Fourier integral which is subsequently evaluated numerically via direct integration along a modified path. The second approach extracts the dominant field...
We develop here a rigorous homogenization approach applied to dense cubic arrays of magnetodielectric spheres, in order to determine their first-principle bulk constitutive parameters. We carefully model their electromagnetic response and assess the validity and limitations of commonly used approximate homogenization models for metamaterials. In particular, we show that, in regimes for which exotic...
CST is a general purpose, computational electromagnetics simulation tool that uses the finite integration technique for its time domain solver. Unfortunately, it does not allow negative ε″ data to be input by a user in the menu window. Consequently, the time domain solver of the current CST version cannot be used to solve the original negative ε″ problem. Here we introduce a manual method to analyze...
This paper presents a new method to improve isolation between two loop antennas with absorber cells exhibiting negative permittivity and permeability at the aimed frequency of 2.45 GHz. The metamaterial (MTM) unit cell was constructed by two open complimentary split ring resonator (OCSRR) and a split ring resonator (SRR) arrangement. The proposed antenna structures were composed of two loop antennas...
An approach to accurate permittivity measurements of compressible materials has been presented. The method uses both the measured, uncompressed density and the calculated, compressed density to account for the change in measured permittivity between compressed and uncompressed specimens of the same material. Normalizing susceptibility to compressed density provides data that closely agreed with actual...
The current work tests the feasibility of using phantom models to detect and determine different blood glucose levels as well as using phantom models to replicate in-vitro results. This is possible since the glucose levels affect the blood's permittivity. Using phantom models, the permittivity characteristics of blood with different glucose levels have been observed to match previous literature as...
Recently introduced concept of active non-Foster metamaterial is reviewed with an emphasis on the counterintuitive background physics. The main fundamental and technological limitations such as stability and selection criteria for active elements are highlighted. It is shown that non-Foster-based active metamaterials are stable if equivalent permittivity or permeability is positive number. Since this...
Several space-time grids with 2D-space are examined for electromagnetic field computation using finite integration (FI) method, where time-step is locally refined. Two-types of space-time grids are proposed to decrease the unphysical reflection of electromagnetic wave. A preliminary stability analysis is also carried out for stable explicit time-marching.
In this paper, we present the results of a freespace microwave inverse scattering experiment. We test the Born Iterative Method algorithm but have modified the cost function and the forward model in a way that fully integrates the inversion algorithm with the antenna model and measurement quantities. This is based on a new integral equation operator that directly links the material contrasts to S-parameter...
We evaluate the performance of two differential time-reversal techniques for detecting, tracking and imaging moving targets in clutter. The proposed techniques provide real-time tracking capabilities with outstanding clutter rejection performance. They also exploit the distinctive features of time-reversal such as superresolution and statistical stability.
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