Electromagnetic Scattering Research Articles

SphericalScattering: A Julia Package for Electromagnetic Scattering from Spherical Objects

SphericalScattering: A Julia Package for Electromagnetic Scattering from Spherical Objects

Uniqueness Results for Some Inverse Electromagnetic Scattering Problems with Phaseless Far-Field Data

Consider three electromagnetic scattering models, namely, electromagnetic scattering by an elastic body, by a chiral medium, and by a cylinder at oblique incidence. We are concerned with the corresponding inverse problems of determining the locations and shapes of the scatterers from phaseless far-field patterns. There are certain essential differences from the usual inverse electromagnetic scattering problems, and some fundamental conclusions need to be proved. First, we show that the phaseless far-field data are invariant under the translation of the scatterers and prove the reciprocity relations of the scattering data. Then, we justify the unique determination of the scatterers by utilizing the reference ball approach and the superpositions of a fixed point source and plane waves as the incident fields. The proofs are based on the reciprocity relations, Green’s formulas, and the analyses of the wave fields in the reference ball.

Fourier Transform of the Lippmann-Schwinger Equation: Solving Vectorial Electromagnetic Scattering by Arbitrary Shapes

In Electromagnetics, the field scattered by an ensemble of particles—of arbitrary size, shape, and material—can be obtained by solving the Lippmann–Schwinger equation. This singular vectorial integral equation is generally formulated in the direct space Rn (typically n=2 or n=3). In the article, we rigorously computed the Fourier transform of the vectorial Lippmann–Schwinger equation in the space of tempered distributions, S′(R3), splitting it in a singular and a regular contribution. One eventually obtains a simple equation for the scattered field in the Fourier space. This permits to draw an explicit link between the shape of the scatterer and the field through the Fourier Transform of the body indicator function. We compare our results with accurate calculations based on the T-matrix method and find a good agreement.

The electromagnetic wave propagation in discontinuous waveguide containing plasma

The current study examines how electromagnetic waves scatter when encountering plasma medium and step-discontinuities. The physical model used in the study includes dielectric and plasma layers separated by horizontal plates made of metallic conducting material. The problem of interest is solved using the Mode-matching technique, which projects the solution onto an orthogonal basis to explain how planar mode excitation is reflected, transmitted, and attenuated. The mathematical and intrinsic power analyses confirm the accuracy of the algebra and solution scheme used. The analysis provides an understanding of both the mathematical and theoretical aspects of the structure under consideration.

A Fast Model Order Reduction Method for Electromagnetic Scattering of Large Periodic Arrays With Connected Elements

A Fast Model Order Reduction Method for Electromagnetic Scattering of Large Periodic Arrays With Connected Elements

Self-Sufficient Algorithm of the Method of Surface Integral Equations in the Problems of Electromagnetic Scattering by Magneto-dielectric Cylinders

Self-Sufficient Algorithm of the Method of Surface Integral Equations in the Problems of Electromagnetic Scattering by Magneto-dielectric Cylinders

Biometric Recognition Based on Hand Electromagnetic Scattering at Microwaves

Biometric Recognition Based on Hand Electromagnetic Scattering at Microwaves

Coronavirus-like all-angle all-polarization broadband scatterer

Creeping waves traveling around a volumetric electromagnetic scatterer provide a significant contribution to its radar cross-section. While quite a few efforts were devoted to suppressing creeping waves as a part of radar countermeasures, here we utilize specially engineered creeping waves to our advantage to create broadband, all-angle, and polarization scatterers. Metalized spherical surfaces, patterned with corona virus-like spikes are designed to provide a broadband constructive interference between the specular reflection and creeping waves, elevating the scattering cross-section. The demonstrated miniature corona scatterers utilize both resonant cascading phenomena and traveling wave interference to tailor electromagnetic interactions, outperforming a resonant dipole in terms of amplitude and bandwidth quite significantly. Our experimental samples are fabricated with an additive manufacturing technique, where a 3D-printed plastic skeleton is subsequently metalized. Micron-thick layers allow governing electromagnetic interactions as if the entire object was made of solid metal. Lightweight, all-angle, all-polarization, and broadband compact scatterers such as these, reported here, have numerous applications, including radar deception, electromagnetic beckoning, and many others.

Electromagnetic Scattering by Arbitrarily Located Electric and/or Magnetic Conducting Double-Strip

The study presents electromagnetic scattering by arbitrarily located double strips with perfect electric and/or magnetic conducting surfaces. The study generalizes not only the physical dimension, location, and orientation of the strips but also, the boundary conditions on each strip are generalized and variable. It can be Dirichlet or Neumann boundary conditions. Since the study considers numerous parameters as the variable, the comparison between the present study and the literature is investigated in detail. Geometries such as parallelly located double strips with fractional boundary conditions, impedance double strips, and wedge problems are considered to compare. Besides, the proposed methodology is compared by the method of moments, the method of auxiliary sources, and the orthogonal polynomials approach. The suggested research investigates the electromagnetic scattering by finite wedge and arbitrarily located two strips with different boundary conditions and widths for the first time since each strip can have different widths and boundary conditions (Dirichlet or Neumann). The results reveal that the angle between the strips, the rotation of the strips, width of the strip have noticeable effects on the scattered field and total radar cross-sections. Between the strips, resonances are observed and their characteristics have a substantial dependency on the boundary conditions.

A High-Order Discontinuous Galerkin Method for Electromagnetic Scattering From Perfectly Conducting Objects in Half-Space

A High-Order Discontinuous Galerkin Method for Electromagnetic Scattering From Perfectly Conducting Objects in Half-Space

An Asymmetrical Mixed Higher-Order Discontinuous Galerkin Time Domain Method for Electromagnetic Scattering from the Plasma Sheath around a Hypersonic Vehicle

The plasma sheath during reentry of hypersonic vehicle is an unmagnetized and weakly ionized nonuniform plasma flow, which causes radio frequency blackout and strong plasma attenuation of electromagnetic wave. The physical properties of the nonuniform plasma flow were obtained using computational fluid dynamics software with unstructured grids. In this study, a detailed computational model was reconstructed with the high-order Lagrange grids for the nonuniform plasma flow region and the high-order Serendipity grids for the homogeneous medium region. In order to calculate the numerical flux between the two types of grids in the discontinuous Galerkin time domain (DGTD) algorithm, an asymmetric high-order element is constructed as a transition unit. Finally, the simulation results in the plasma sphere show that the above method improves the computational accuracy and decreases calculation. The amplitude and scattering about electromagnetic wave in nonuniform plasma flow are clarified in detail. It is suggested that the presented method could be an effective tool for investigating interaction between electromagnetic waves and plasma flow.

Enhancement of Electromagnetic Scattering Computation Acceleration Using LSTM Neural Networks

This paper presents the electromagnetic long short-term memory neural network (EM-LSTMNN) approach to accelerate radar cross-section (RCS) calculations in optimizing low RCS for electrically large targets. The proposed method converts the conventional electromagnetic numerical calculation into an efficient numerical calculation using the LSTM neural network, resulting in a significant improvement in RCS computation speed. To assess the effectiveness of this approach, a downscaled model of a large-sized ship is employed as the target for low RCS optimization. Each modification made to the target’s mesh data during the optimization process is stored in the dataset as a new element. As the ship scaling model undergoes modifications during the optimization process, the new mesh data are recorded, thus adding a new element to the dataset at each time step. This forms a time series representation of the mesh model. By utilizing the dataset collected throughout the optimization process, the proposed EM-LSTMNN model is trained using data-driven approaches, with a training time of approximately 106 s. It is worth noting that this training time is significantly smaller compared to existing methods that employ fully connected neural networks. The performance of the proposed approach is demonstrated by comparing the RCS calculation results obtained through this method with those obtained through traditional electromagnetic simulations.

Observations of plasma waves generated by charged space objects

A sampling of the environment around inert space objects has determined, which linear and nonlinear waves are created by moving space debris of all sizes. Plasma waves excited by satellites and space debris moving through the Earth's plasma in low earth orbit have been measured with in situ electric field sensors on other satellites. These orbit driven plasma waves are of interest for proximity detection of space debris and sources of electrostatic and electromagnetic noise on spacecraft. Satellites and other space objects moving through the near-earth ionosphere between 200 and 1000 km altitude become electrically charged by both electron collection and photo emission in sunlight. These hypersonic, charged objects can excite a wide range of plasma waves. Measurements with the Radio Receiver Instrument (RRI) on the Swarm-E satellite have shown that electromagnetic plasma waves from known objects can be observed out to ranges of tens of kilometers. The amplitude, spectral, and polarization changes of the RRI data are consistent with electromagnetic, compressional Alfvén waves launched by charged space objects traveling across magnetic field lines. In addition, electrostatic lower hybrid waves or nonlinear ion acoustic pinned oscillations may have been self-generated and measured on the Swarm-E satellite. It is proposed that measurements of these waves with local electric field measurements or remote electromagnetic wave scatter may be useful to design systems for the location of orbiting objects. Spatial and temporal details of spacecraft charging are key to understanding the extent of waves associated with the object motion in space plasmas.

On the Direct Electromagnetic Scattering Problem by an Impenetrable Partially Coated Obstacle Embedded in a Chiral Environment

On the Direct Electromagnetic Scattering Problem by an Impenetrable Partially Coated Obstacle Embedded in a Chiral Environment

Quantitative Analysis of Super Resolution in Electromagnetic Inverse Scattering for Microwave Medical Sensing and Imaging.

Microwave medical sensing and imaging (MMSI) has been a research hotspot in the past years. Imaging algorithms based on electromagnetic inverse scattering (EIS) play a key role in MMSI due to the super-resolution phenomenon. EIS problems generally employ far-field scattered data to reconstruct images. However, the far-field data do not include information outside the Ewald's sphere, so theoretically it is impossible to achieve super resolution. The reason for super resolution has not been clarified. The majority of the current research focuses on how nonlinearity affects the super-resolution phenomena in EIS. However, the mechanism of super-resolution in the absence of nonlinearity is routinely ignored. In this research, we address a prevalent yet overlooked problem where the image resolution due to scatterers of extended structures is incorrectly analyzed using the model of point scatterers. Specifically, the classical resolution of EIS is defined by the Rayleigh criterion which is only suitable for point-like scatterers. However, the super-resolution in EIS is often observed for general scatterers like cylinders, squares or Austria shapes. Subsequently, we provide theoretical results for the Born approximation framework in EIS, and employ the Sparrow criteria to quantify the resolution for symmetric objects of extended structures. Furthermore, the modified Sparrow criterion is proposed to calculate the resolution of asymmetric scatterers. Numerical examples show that the proposed approach can better explain the super-resolution phenomenon in EIS.

Mathematical Theory for Electromagnetic Scattering Resonances and Field Enhancement in a Subwavelength Annular Gap

Mathematical Theory for Electromagnetic Scattering Resonances and Field Enhancement in a Subwavelength Annular Gap

The Electromagnetic Scattering Problem by a Cylindrical Doubly-Connected Domain at Oblique Incidence: An Inverse Problem

In this work, we examine the inverse problem to reconstruct the inner boundary of a cylindrical doubly-connected infinitely long medium from measurements of the scattered electromagnetic wave in the far-field. We consider the integral representation of the solution to derive a non-linear system of equations for the unknown radial function. We propose an iterative scheme using linearization and regularization techniques.

Static Surface Mode Expansion for the Electromagnetic Scattering From Penetrable Objects

Static Surface Mode Expansion for the Electromagnetic Scattering From Penetrable Objects

Multibranch Curvilinear Rao–Wilton–Glisson Basis Functions for Electromagnetic Scattering From Perfect Electric Conducting Targets

A multibranch curvilinear Rao-Wilton-Glisson (MB-CRWG) basis function is proposed to solve surface integral equations (SIEs) with nonconformal curvilinear meshes. The derivation of the MB-CRWG basis function is given. The structure of the MB-CRWG basis function can be divided into positive and negative parts. The positive part is one curvilinear triangular patch, and the negative part is composed of several curvilinear triangular patches. The MB-CRWG can conveniently connect two surfaces discretized with curvilinear triangular patches of different sizes. Numerical examples on the electromagnetic scattering from multiscale perfect electrically conducting (PEC) targets are given to demonstrate the effectiveness of the proposed basis function.

Characteristic Mode Analysis: Application to Electromagnetic Radiation, Scattering, and Coupling Problems

Characteristic Mode Analysis: Application to Electromagnetic Radiation, Scattering, and Coupling Problems