L. Nickelson

MICROWAVE SCATTERING AND ABSORPTION BY A MULTILAYERED LOSSY METAMATERIAL-GLASS CYLINDER

Here we present the rigorous electrodynamical solution of difiraction problem about the microwave scattering by a multilayered cylinder. The number and thickness of layers is not limited. We ofier the solution when the central core of multilayered cylinder can be made of difierent isotropic materials as a metamaterial, a ceramic matter or a semiconductor as well as of a perfect metal. The isotropic coated layers can be of strongly lossy materials. The signs of the complex permittivity and complex permeability can be negative or positive in difierent combinations. Here we present dependencies of the scattered power of the incident perpendicularly and parallel polarized microwaves by the metamaterial-glass cylinder on signs of metamaterial permittivity as well as permeability. The glass layer absorbed power and metamaterial core absorbed power dependent on the hypothetic metamaterial permittivity and permeability signs at the wide range frequencies 1{120GHz are also presented here. The metamaterial core of cylinder has a radius equal to 0.0018 m and the thickness of the coated acrylic-glass layer is 0.0002m. We have found some conditions when the scattered-power has minimal values and the absorbed power by the coated acrylic glass layer is constant in a very wide frequency range. We have discovered that the glass layer absorbed power increases with increasing of the frequency at the range 1{120GHz for both microwave polarizations.

SIE Method of Analysing Microwave Fields of a 3D Heart Model

The Singular Integral Equations Method (SIE) used in this article allowed us to solve Maxwells Equations for a Three-Dimensional (3D) asymmetric heart model when a microwave catheter (MC) was placed inside the model and radiated microwaves. Here we explain the main idea of our SIE method. We first separated the solution of equations from satisfying the boundary conditions. For this purpose, we found the solution of the differential equations having a point source. This fundamental solution is used in our integral representation of a problem. The integral representation automatically satisfied the differential equations but has an unknown density function which must be found from the boundary conditions. The solution of the differential equations, obtained by our SIE method, was rigorous, that is it satisfied the differential equations and all boundary conditions. The false roots did not occur when applying our SIE method.All surfaces of the heart model were defined as a triangular mesh covering the 3Dheart surfaces. The heart model consisted of cardiac muscle and the right and left atriums with ventricles which were filled with blood. In this article we presented our calculations of the microwave electric field inside of a heart model. We have seen that our SIE method enabled one to optimal the size and shape of a MC when used to remove abnormal tissue in a heart model. We discovered that the electric field distribution most suitable for microwave ablation was a curved microwave catheter pressed against the lateral surface of heart atrium.

Electrodynamical Analysis of Open Lossy Metamaterial Waveguide and Scattering Structures

Large stream of articles devoted to the study of metamaterial waveguide and metamaterial scattering (reflecting) structures points that there is a need for development devices possessing unique characteristics, as multifunctionality, reconfigurability, certain frequency bandwidth, ability to operate at high-powers and high-radiation conditions. The importance of diffraction problems for scattering structures is based on their great practical utility for many applications, such as reflector antennas, the analysis of structures in open space, electromagnetic (EM) defence of structures, the scattering modeling for remote sensing purposes, high frequency telecommunications, computer network, invisibility cloaks technology and radar systems (Li et.al., 2011; Zhou et.al.; 2011, Zhu et al., 2010; Mirza et al., 2009; Abdalla & Hu, 2009; Engheta & Ziolkowski, 2005).

ANALYSIS OF OPEN MICROSTRIP AND SLOT LINES WITH SEMICONDUCTOR SUBSTRATES

The numerical study of open microstrip lines (MSLs) and slot lines (SLs) with n -Si substrates. Two methods of singular integral equations (SIE) were used in our calculations. The first method we used for solving a problem was based on TEM-approximation and the second method was electrodynamically rigorous. The algorithms that we applied in our computations allowed us to take into account the finite substrate width and the finite metal strip thickness. The electrodynamical characteristics of MSLs on the specific resistivity of the substrate material, the metal strip width, the distance between the metal strip and the substrate lateral edges were investigated in this article. Also the dispersion dependences were determined for the main and higher modes of a noncoplanar SL and coplanar SLs. We presented characteristics of open MSLs and SLs having different crosssections to show the algorithm efficiency. The calculated and measured results agreed when compared to one another.

The computation of electrical fields on a heart model with a microwave catheter

In our paper, we calculated the distribution of an electric field modulus at several parallel cross-sections of a model heart (with a catheter inside of its right atrium). The catheter was created out of dielectric or metal material. The frequency of the microwave signal was f = 10 GHz. The distribution of the electric field modulus has resonance peaks. The electric field could be concentrated in different places of the heart depending on weather the material of the catheter was dielectric or metal.

Electromagnetic analysis of the main and higher modes on the onion-like carbon tubes

ABSTRACT The electric and magnetic field distributions as well as the dispersion characteristics of open cylindrical tube (hollow-core) waveguides are analysed in this work. The analysed waveguides are made of an onion-like carbon (OLC) material. The solution of the boundary problem was fulfilled by the partial area method. It was discovered the very complicated dependencies of the phase and attenuation constants on the waveguide radii. Such dependencies arise because the OLC material is the highly dispersive and absorbing one. The fundamental and four higher modes can propagate in our investigated waveguides. We have analysed the high-frequency cut-off frequency of modes that is dependent on the tube waveguide external radius. The certain electromagnetic (EM) mode can propagate only on the frequencies lower than the mentioned cut-off frequency. For this reason, this cut-off frequency has an important use in practical applications. We presented here the EM field distributions of modes. We discovered that it is possible to reach the one-mode regime of OLC tube waveguide at the certain external radius. The fundamental and first higher modes’ EM energy is concentrated in the OLC material between the internal and external surfaces of the waveguide.

An Electrodynamical Analysis of a Model Heart

Presents a numerical analysis of an electrodynamical problem. The problem was solved by using our Singular Integral Equations’ Method. We formulated the problem in this way. A metal microwave catheter (antenna) was placed inside of a three dimensional asymmetric model heart. The catheter radiated a microwave with a frequency of 10 GHz. The model heart was limited by a noncoordinate shape surface. The model heart consisted of two different size cavities. The heart cavities were schematic images of the left and right atriums and ventricles. In our calculations the cavities were filled with blood and the walls of the heart consisted of myocardium tissue. In this article we analysed four model electrodynamical problems that could be used in medical microwave ablation. Several different dependences of electric field distributions were investigated at different locations and shapes of microwave catheters at two cross-sections of the heart. Our calculations showed that the electric field distribution was best suited for the ablation when we used a curved catheter that touched the inner wall of the heart. Ill. 6, bibl. 11 (in Lithuanian; summaries in Lithuanian, English, Russian).

Anomalous Phase and Attenuation Constants of SiC Rod Waveguide at Higher Temperatures

Here we present the dependences of the phase and attenuation constants of silicon carbide (SiC) cylindrical rod waveguide upon frequency at di erent temperatures, i.e. T = 1800 ◦C and T = 1900 ◦C when the rod radius is relatively large. We have also calculated the electric and magnetic eld distributions at di erent frequencies in order to explain the anomalous attenuation. The SiC rod waveguide was investigated by the partial area method. The complex roots have been found by the Muller method. Computer codes for calculations were written in MATLAB language.

Dispersion dependencies of circular hollow-pipe SiC waveguide on the inner radius and temperature

The dispersion dependencies of circular hollow-pipe silicon carbide (SiC) waveguide on the inner radius of the circular opening and the temperature are presented here. The electrodynamical problem was solved by the partial area method. All calculations of present work were fulfilled by our MATLAB code Here were investigated SiC waveguides with r = 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm at temperatures T = 20°C, 500°C, 1000°C. The external radius of analyzed waveguides is equal to 2.5 mm. The comparison of phase and attenuation constants for the whole rod SiC waveguide and the hollow - pipe SiC waveguide with two different inner radii r of openings is presented here. The broadbandwidth of hollow - pipe SiC waveguide is higher comparing with the whole rod SiC waveguide. The broadbandwidth of the analyzed hollow - pipe SiC waveguide considerably grows with increasing of the inner waveguide radius r. The phase and attenuation constants have higher values when the temperature is higher at the most frequencies intervals.

Extraordinary dependences of dispersion characteristics of lossy SiC cylindrical waveguide on the radius

Here we for the first time present the dependencies of the dispersion characteristics of the main mode propagating in a lossy cylindrical waveguide on its radius. The waveguide is made of absorbing microwave silicon carbide (SiC) material. The dispersion characteristics of ceramic SiC waveguide were investigated by the partial area method. The complex roots of the dispersion equation are found by the Muller method. The calculations were fulfilled at the waveguide radii equal to 0.5, 1.0, 1.5, 1.9, 2, 2.1, 2.9, 3, 3.1 mm when the temperatures are 1850°C and 1900°C. We discovered that the dependencies of complex longitudinal propagation constant have an unusual protrusion at some waveguide radii at very higher temperatures. The area of anomaly dispersion shifts to the lower frequencies when the radius increases.