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Rigorous solutions of electromagnetics problems involving lossy dielectric objects are considered. Problems are formulated with two recently developed formulations, namely, the combined-tangential formulation (CTF) and the electric and magnetic current combined-field integral equation (JMCFIE), and solved iteratively using the multilevel fast multipole algorithm (MLFMA). Accuracy and efficiency of...
In this paper, a novel MoM-based procedure is developed for efficient treatment of scattering problems over a wide frequency band, including very low frequencies where many of the conventional algorithms often fail. The proposed approach, based on closed-form expressions for the evaluation of the fields radiated by rooftop basis functions, is demonstrated to be universally applicable to conducting...
During the past decades, much research has been done towards the efficient calculation of impedance integrals in the Method of Moments. However, these results were almost always uniquely concerned with penetrable media. In this contribution, it will be shown how the integrals can be treated in highly conductive media as well. The rapid exponential decline of the Green's function, due to the losses,...
In this paper, we present the discretization in Method of Moments of the Electric-Magnetic Field Equation with the divergence-Taylor-Orthogonal basis functions, a facet-oriented set of basis functions. We show for a sharp-edged object that the computed RCS with this discretization offers better accuracy than the Loop-Star discretization.
A new integral equation formulation is presented for the analysis of capacitive waveguide components, including metallic and dielectric objects. The technique exploits the symmetry of the structure by formulating a 2D scattering problem with oblique angle of incidence. As a consequence, the analysis of complex waveguide capacitive devices results to be very efficient, as compared to other 3D numerical...
In this paper, a multi-grade-oriented accelerating strategy with adaptive cross approximation (ACA) algorithm is presented for enhancing the efficiency of Calderón multiplicative preconditioner (CMP). CMP is a very successful preconditioner for stabilizing EFIE and easy to embed in conventional MoM codes. However, because of the complicated nature of this preconditioner, it gives rise to enormous...
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...
In this paper, the use of the multiple sweep method of moments (MSMM) is proposed to design collinear dipole antenna arrays in free space. The genetic algorithm (GA) is cooperated to find the optimum array parameters. The antenna design is focused on non-uniform spacing collinear dipole antenna arrays. Under this appropriate combination (MSMM/GA), numerical results are presented to demonstrate its...
This paper discusses a numerical investigation in connection with the dependency of the condition number of the impedance matrix on the decomposition of current on a multiplet, a junction with several attached wires. It is shown that the condition number is frequency- and wire selection dependant, and it is possible to minimize it, and that this helps to minimize the condition number of the system...
This contribution describes a security assistant system comprising distributed millimeter wave radar sensors and chemical sensors. The system is deployable for a wide range of security applications, e. g. passenger security checks on airports, surveillance of people crowds in mass transportation systems or in other security-sensitive areas. The system looks for body-worn hazardous chemical substances...
In this paper we present the findings of an effort to create a millimeter-wave radar system to image the internal structure of a kraft recovery boiler as well as measure the dielectric coating on the pipes. A kraft boiler is used by the paper industry to reclaim inorganic salts used in the pulping of wood. The bio-mass and salt structure of the fuel combusted in the boiler causes rapid deposition...
By using the transmitters of opportunity, passive radar systems allow target detection and tracking without transmitting any RF energy. This approach ensures covert operation of the radar thus decreasing the risks of enemy detection and electronic countermeasures. In a nutshell, the passive radar utilizes the existing broadcast signals from multiple FM radio and TV transmitters, detects backscattered...
In this study, two different applications are performed. An application of concealed object detection is firstly studied through millimeter-wave inverse synthetic aperture radar (ISAR) imaging. For this purpose, near-field W-band ISAR measurements of one centimeter metallic and dielectric cube targets covered by distinct textile materials are carried out in an anechoic chamber room. Then, the images...
A comparative study is carried out between two numerical simulation techniques—the surface integral equation (SIE) and the finite-difference time-domain (FDTD) methods—in order to characterize rough surface ground clutter relevant to forward-looking radar applications. Computational deficiencies in the SIE approach for analyzing scattering effects at grazing angles are outlined; motivations for the...
An efficient Nyström scheme is developed for the numerical solutions of electromagnetic (EM) scattering by conducting rough surfaces based on Monte Carlo simulation frame. A series of sample surfaces with desired roughness is first created with computer codes and then the magnetic field integral equation (MFIE) is solved with the Nyström scheme for each sample surface. Since several hundreds of realizations...
We investigate image enhancement of transmitted optical fields though plasmon film lenses with smooth surfaces, random rough surfaces, and sinusoidal rough surfaces. We show that the silver film lens with small periodic roughness can provide image enhancement. Image enhancement is defined by the spatial width of the image in the image plane. It is shown that the spatial width can be significantly...
A hybrid UV/PBTG/SMCG method is developed based on the Numerical Solution of Maxwell Equation in 3D Simulations (NMM3D) of electromagnetic wave scattering by Gaussian dielectric random rough surfaces with exponential correlation functions. In 3D simulations, the height function z=f(x,y) of the rough surfaces vary in both two horizontal directions. The method inherits the advantages of the UV method,...
Brillouin precursors are formed as an ultrawideband pulse propagates in lossy dispersive media. The impact of rough surface on Brillouin precursors is studied when a modulated rectangular pulse illuminates a one-dimensional rough surface of the lossy dispersive medium. Due to the interaction between the incident wave and the rough surface, the time delays and the signal waveforms are distinct at different...
Biomedical industry is in continuous growth in the last few years. This paper presents new compact printed antennas for medical applications. Low profile compact antennas are useful in the development of human biomedical systems. Design considerations, computational results and measured results of several wideband microstrip antennas with high efficiency for medical applications are presented in this...
This paper presents a broadband microstrip fed printed dipole antenna with back radiation properties. Printed dipole employs a microstrip fed line which simplifies the feeding mechanism of the antenna. By modifying the feed line broadband nature is achieved. A reflector is used to give backward radiation that makes this antenna as a feed for reflector antenna.
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