PEC Cylinder Research Articles

Directivity Enhancement and Excitation of Space Wave, Leaky Wave, and Creeping Waves for a PEC Cylinder Coated With a Uniaxial Dielectric

Directivity Enhancement and Excitation of Space Wave, Leaky Wave, and Creeping Waves for a PEC Cylinder Coated With a Uniaxial Dielectric

The Spectral Integral Method (SIM) for the Scattering from an Arbitrary Number of Circular PEC Cylinders

The Spectral Integral Method (SIM) for the Scattering from an Arbitrary Number of Circular PEC Cylinders

Convergence Analysis of the Currents and Fields Involved in the Method of Auxiliary Sources Applied to Scattering by PEC Cylinders

The method of auxiliary sources (MAS) is an established technique for the numerical solution of electromagnetic shielding and scattering problems exhibiting an increasing interest for the simulation of various electromagnetic compatibility (EMC) applications. In previous works, it was shown that for the problem of transverse magnetic illumination of a perfect electric conducting cylinder by an electric current filament, it is possible for large numbers N of auxiliary sources that the MAS currents diverge and oscillate, while the generated MAS field converges to the exact solution. In this article, we further analyze the convergence issues and oscillations encountered in the MAS by considering the transverse electric case due to excitation by a magnetic current filament. We demonstrate analytically that the convergence/divergence phenomena of the currents and fields also occur in this problem and then study the nature of this divergence in detail. In particular, we prove a large-N asymptotic formula for the divergent MAS currents, which captures accurately the important characteristics of the associated inherent oscillations. Numerical results for noncircular shapes are also presented. The discussed effects must be carefully taken into account in EMC simulations pertaining to cylindrical conductors.

Improving performance of mantle cloak for electrically large PEC cylinders by reducing higher-order scattering coefficients

Based on the scattering cancellation technique, an approach is proposed to improve the mantle cloak’s performance for electrically large cylinders. The procedure is based on the observation that the number of dominant scattering coefficients and corresponding magnitudes for a cylinder decreases when oriented obliquely to the incident wave. Thus, it is quite advantageous to design a mantle cloak under the oblique incidence than the normal incidence. The proposed method starts with determining the optimum angle of incidence at which if the object is oriented with respect to the incident wave, the maximum scattering reduction can be obtained with a mantle cloak explicitly designed for that orientation. The procedure is applied to cylinders of radii and , where is the design wavelength. The proposed approach’s advantages are highlighted by comparing it with the previously published literature. Additionally, the mantle cloak is realized using a periodic grid of metallic patches, and simulations in Ansys HFSS are performed to verify the design.

A modification of the method of magnetic field integral equations for analysis of wave scattering by PEC cylinder of arbitrary cross-section

A modification of the method of magnetic field integral equations for analysis of wave scattering by PEC cylinder of arbitrary cross-section

Two-Dimensional Scattering From Homogenous Anisotropic Cylinders Using a Multifilament Current Method

Implementation of the multifilament current method (MFCM) to analyze the scattering from homogeneous anisotropic cylinders is introduced. The ${z}$ -directed electric and magnetic line sources are used to associate with TM and TE polarizations, respectively. The radiation fields of a line source in unbounded space occupied with an anisotropic material are derived in detail. With the help of the derived fields, the application of the MFCM is expanded to anisotropic materials. The scattering field is then obtained in terms of these line sources. Monostatic and bistatic scattering widths of cylinders with and without sharp edge are investigated under different incident wave polarizations and material characteristics. Apart from homogeneous anisotropic cylinders, the scattering from an anisotropic shell-coated PEC cylinder is also straightforwardly analyzed without additional considerations in the formulation. The oscillation phenomenon of filament currents in representing the scattered fields and the ill-conditioned issue of the constructed matrix are also discussed in detail. Numerical results obtained with this proposed scheme are also in good agreement with published ones, whereas the proposed technique has its merits on simplicity and conciseness in comparison to the existing numerical methods.

Numerical approach to approximate the electromagnetic scattering from random PEC cylinder placed below in dielectric half-space

A numerical solution is presented for electromagnetic scattering from a random cross-section of a cylinder placed inside a dielectric half-space. Assumed that a plane wave of known parameters is incident from the half space. The incident electric field of an electromagnetic plane wave is parallel to the z-axis of the random cylinder. The method of moment is employed to obtain surface currents and Electric field integral solution is used to obtain the scattered field. The problem consists of two regions, the observer located in the free space region above from interface and the second region is an underground region where the random cylinder is placed. In the whole scenario, the medium is considered as homogeneous and lossless. The average scattered field is observed by varying different parameters for realization. To diversify the solution, COMSOL Multiphysics® and Matlab is used for simulations to investigate backscattered field involving transverse electric (TE) and transverse magnetic (TM) polarizations.

Optimized cloaks made of near-zero materials for different-sized concealed targets

The optimized cloaking design for conducting cylinders of different sizes is studied based on the Mie scattering theory. We construct a concentric multi-layered cloak made of alternating materials with isotropic dielectrics and epsilon-near-zero (ENZ) material, the thickness of which can be determined through genetic algorithm. As the radius of the conducting cylinder increases, high order scattering contributions are becoming evident, and more layers are needed. The scattering cross sections of three different radii of PEC cylinders are minimized by utilizing different numbers of multi-layers respectively. We find that eight or less optimized layers can cancel most of the scattering from a conducting cylinder with its dimension compared to wavelength, and more effectively when taking the ENZ material as the inner starting shell. The frequency dependence of total scattering is also studied, leading to the result that the bandwidth decreases as the size of concealed PEC cylinder increases. Furthermore, it is shown that the cloaking efficiency is less sensitive to the permittivity and thickness of the ENZ material, due to the small phase variation in the ENZ material. The multi-layered cloak designed for a PEC target can also be used to evidently reduce the scattering of a dielectric core and design a multi-layered elliptical cloak.

Asymptotic Diffraction of a PEC Cylinder Located at a Plane Interface Between Isorefractive Half-Spaces

Isorefractive material has some novel properties. We consider the case of a plane wave scattered by a circular cylinder located at a plane interface between isorefractive half-spaces. We mainly study the high-frequency asymptotic diffraction contribution extracted from the series’ expression. We prove that the extracted asymptotic contribution conforms to the classical asymptotic diffraction theory.

Average scattered field from a random PEC cylinder buried below a slightly rough surface

Scattering from a perfect electric conducting cylinder with random radius buried below a half space dielectric homogenous interface is studied. The cylindrical wave scattered by cylinder is expanded in terms of plane wave spectrum. Small perturbation method is used to study the interaction of each plane wave with the interface. The zeroth order term yields solution for a flat interface, whereas scattering from a rough surface is given by first-order term. Results are obtained for both TM and TE polarizations. Analytical expressions of the average scattered field are obtained and verified using numerical evaluation. Different scattering scenarios are simulated by varying the distribution of the radius. It is observed that average scattering cross section of an ensemble with normal/uniform distribution is almost equal to that of a cylinder with mean radius.

Finite-difference time-domain modeling of curved material interfaces by using boundary condition equations method**Project supported by the National Natural Science Foundation of China (Grant No. 51025622).

To deal with the staircase approximation problem in the standard finite-difference time-domain (FDTD) simulation, the two-dimensional boundary condition equations (BCE) method is proposed in this paper. In the BCE method, the standard FDTD algorithm can be used as usual, and the curved surface is treated by adding the boundary condition equations. Thus, while maintaining the simplicity and computational efficiency of the standard FDTD algorithm, the BCE method can solve the staircase approximation problem. The BCE method is validated by analyzing near field and far field scattering properties of the PEC and dielectric cylinders. The results show that the BCE method can maintain a second-order accuracy by eliminating the staircase approximation errors. Moreover, the results of the BCE method show good accuracy for cylinder scattering cases with different permittivities.

Scattering by a PEMC cylinder embedded in lossy medium

Scattering of electromagnetic waves from two-dimensional cylinder composed of perfect electromagnetic conductor (PEMC) material has been studied. Here, we analyze the scattering width of the two dimensional PEMC cylinder in terms of co-polarized and cross-polarized fields. Using the duality transformation which was introduced by Lindell and Sihvola, is made for the scattered field by a PEC cylinder embedded in Soil. As an application, plane wave scattered from a planar interface of air and PEMC medium is studied. We studied that PEC and PMC are the limiting cases of PEMC, where there is no cross-polarized component. An attempt has been made to verify the PEMC results by the different values of the parameter M and Mη0.

A Source-Type Best Approximation Method for Imaging Applications

In this letter, we embark on solving the inverse source problem for electromagnetic (EM) waves with application to target detection. The best approximate solution is derived in terms of the singular value decomposition (SVD) of the direct integral operator, while avoiding any optimization or iterative scheme. Inherent complications in the process are also expressed. The spectral cutoff regularization method is employed to overcome the ill-posed nature of the integral equation. The algorithm is applied to the detection and localization of infinitely long PEC and dielectric cylinders demonstrating robustness under noise impact.

EM Scattering From Cylindrical Structures Coated by Materials With Inhomogeneity in Both Radial and Azimuthal Directions

Consider a cylindrical structure with an arbitrary core coated by layers with inhomogeneity in both radial and azimuthal directions in the most general case. The core of the structure may be PEC, PMC, PEMC, impedance surface, dielectric, or metamaterial and an electromagnetic (EM) wave with arbitrary polarization is obliquely incident on the structure. In this paper, EM scattering from such a structure is analyzed, for the first time, through a general method in the frequency domain on the basis of the Taylor series concept. The validity of the proposed method is verified through some comprehensive examples. It is confirmed that the method is simple, fast, and highly reliable. Moreover, it is capable of analyzing the scattering of obliquely incident plane waves for all types of cylindrical cores and lossy inhomogeneous layers with continuous dielectric and magnetic profiles. In the last example, to show the applicability of the proposed method in inverse problems, the method is employed in an optimization procedure to reduce the radar cross section of a PEC cylinder.

Mathematical formulation for transparency and maximum scattering from bilayer MTM-coated PEC cylinders

In this paper, a novel formulation interval to design multilayer metamaterial (MTM) radar absorbers and shields in cylindrical structure is presented. In this proposed approach, the interaction of electromagnetic waves by an infinitely long perfect conducting cylinder coated with bilayer MTM is investigated. Transparency and maximum scattering conditions for the structure, under a normally uniform plane wave with transverse electric, transverse magnetic and circular polarizations, are mathematically extracted by using small argument forms of Bessel and Hankel functions. In transparency, the capability of radars is dissipated by the full transmission of the incident waves back to the direction from which they were radiated. On the other hand, scattering maximization by diffuse reflection and making chaff, confuses the radars in target detection. Theoretical formulations are verified by COMSOL which is full wave software. However, our formulations are proved for electrically small cylinders, but simulation results show that they are useful for cylinders with dimensions compared to the wavelength.

On the investigation of scattered field from coated PEC cylinder buried beneath slightly rough surface

An analytic technique based on spectral plane wave representation of fields (SPRF) for the scattering of a plane wave from aperfectly electric conductor (PEC)cylinder coated withdouble positive (DPS)or double negative (DNG) materialsburied beneath a slightly rough surface is formulated. Small Perturbation Method is used to consider scattering from rough surface. Spectral integrals are evaluated using saddle point method. A comparison with the previously available results has been done for validity. Both TM and TE polarizations are considered to obtain results varying different geometrical and physical parameters.

Symmetric Absorbers Realized as Gratings of PEC Cylinders Covered by Ordinary Dielectrics

Nearly all known electrically thin perfect absorbers are asymmetric with respect to their two sides and show perfect (rather, nearly perfect) absorption only from one side of the absorbing layer. Moreover, the vast majority of the designs contain a ground plane, which makes the transmission coefficient zero at all relevant frequencies. Here, we introduce a simple symmetric configuration of a single infinite grating of perfectly conducting rods coated by ordinary dielectrics as a symmetric single-layer perfect absorber not containing any impenetrable layers. With the goal to examine its capacity to absorb electromagnetic radiation, we replace each cylinder by a pair of dipole lines and derive the conditions for the perfect absorption (zero reflection and zero transmission) in terms of their dipole moments. It is a general approach that is not limited to circular cylinders or homogeneous textures; in this way, the generic concept of carrying over properties from simpler to more complicated structures, is realized. A metric of fulfilling the aforementioned two requirements for perfect absorption is defined and evaluated for a number of different cases. A realistic example design demonstrating 96%-97% absorption is presented. The performance can be increased further to reach 98% absorption in case of permitting arbitrary permittivities.

Analysis of scattering from cylindrical structures coated by radially inhomogeneous layer using Taylor’s series method

Consider a cylindrical structure with an arbitrary core coated by a radially inhomogeneous layer in a general case. The core of the structure may be PEC, PMC, PEMC, impedance boundary, dielectric, or metamaterial. Contrary to the scattering problems of homogeneous media, scattering problems of inhomogeneous media do not have exact solutions except for special inhomogeneous profiles. In this paper, a general frequency domain method is proposed to analyze scattering from such structures on the basis of Taylor’s series concept for obliquely incident electromagnetic (EM) waves with arbitrary polarizations. The validity of the suggested method is verified by comparison with the exact solutions of some special profiles for the coating layer. Furthermore, a comparison is made between the proposed method and other commonly used methods in the literature, which confirms that the proposed method is general, fast, and has good convergence toward the solution. Moreover, as an application, we employed the method for optimization of the scattering echo width of a PEC cylinder.

A New Efficient Technique for Transient Scattering of Conducting Cylinders Illuminated by a TM-polarized Plane Wave

In this letter, the transient analysis of infinite conducting cylinders in free space is obtained by solving the time-domain electric field integral equation (TD-EFIE) via a time-domain method of moments (TD-MoM). The PEC cylinders with arbitrary cross section are illuminated by a transverse magnetic (TM)-polarized Gaussian plane wave. The temporal basis function is triangular, and the spatial basis function is rectangular. The two-dimensional Green's function is employed to develop the TD-MoM formulation. Two different approximations are used to calculate the self-coupling terms of the impedance matrix. It is shown that the time convolution integrals and self-terms involved in the formulation can be evaluated analytically to increase the accuracy and the stability of the proposed technique.

Scattering of electromagnetic plane wave from a chiral cylinder placed in chiral metamaterials

Analytical solution of vector wave equation describing the scattering of electromagnetic plane waves from an infinitely long circular chiral cylinder placed in another chiral metamaterial is presented. Cylindrical vector wave functions are used to express the fields both inside and outside the circular cylinder. The unknown are determined by applying the appropriate boundary conditions at the cylindrical interface. The numeric results are presented taking different combinations of metamaterials for inner and outer mediums of the cylinder. For this purpose chiral and/or chiral nihility cylinder placed in chiral and/or chiral nihility mediums are considered. Extreme cases of permittivity and permeability corresponding to PEC and PMC cylinder are also considered.