Components Of Scattered Field Research Articles

An Interpretation Method on Amplitude Intensities for Response Waveforms of Backward Transient Scattered Field Components by a 2-D Coated Metal Cylinder

An Interpretation Method on Amplitude Intensities for Response Waveforms of Backward Transient Scattered Field Components by a 2-D Coated Metal Cylinder

Interpretation Method of Inversion Phenomena on Backward Transient Scattered Field Components by a Coated Metal Cylinder

Interpretation Method of Inversion Phenomena on Backward Transient Scattered Field Components by a Coated Metal Cylinder

Scattering evaluation of an infinite PEC plane coated with an anisotropic medium under arbitrary source excitation

A spectral-domain asymptotic method based on the dyadic Green’s function is proposed to study the electromagnetic (EM) scattering of an infinite perfectly conducting (PEC) plane coated with a uniaxial electric anisotropic medium (UEAM) under arbitrary source excitation. We specifically analyze the ray propagation path of the incidence wave from the individual point source, which acts at the planar-layered medium structure to obtain the dyadic Green’s functions (DGFs) of different types of EM waves. These DGFs from the reflected, transmitted, and entire secondary scattered fields are employed to establish the relationship between the arbitrary excitation source and different types of scattered fields. According to the corresponding “source-field” connection between the excitation source and the scattered field components in the spectral domain, we can first derive the expression of the spectral-domain DGF matrix components and then use the saddle point method to obtain the spatial-domain dyadic Green’s function. Finally, we use the integral equation solution to construct the scattered field for an infinite PEC plane coated with the UEAM layer under arbitrary source excitation. The comparison of simulation results from the proposed method and the method of moments (MoM) method confirms the algorithm validation. So it is expected to be a valid algorithm for dealing with electrically large and complex targets coated with the UEAM layer under any source excitation in the future.

Radar Cross Section (RCS) of perfect electromagnetic conductor (PEMC) cylinder by a Laguerre–Gaussian beam

Radar Cross Section (RCS) of perfect electromagnetic conductor (PEMC) cylinder using an incident Laguerre–Gaussian (LG) beam has been investigated. LG beam potential function is used to expand the incident and scattered electromagnetic (EM) field components. The co- and cross-polarized scattered field coefficients are determined by applying the PEMC boundary conditions at the interface i.e., 𝑟=𝑎. The obtained values for co- and cross-polarized scattered field components would be helpful to find out the scattered field distribution. A comparison of our results for PEMC and PMC for fundamental LG beam with beam mode 𝑝=0, 𝑙=0, i.e., 𝐿𝐺00 match with the gaussian beam scattering as witnessed in published work. The effects of OAM mode index (𝑙), beam waist radius (𝑤0), and PEMC cylinder radius on RCS have been analyzed.

Speed-up of scattered field formulation of FDTD method combining with time-domain EFIE by using spherical harmonic expansion of Green’s function

This paper proposes a scattered field formulation of the finite-difference time domain method (S-FDTD) combining with a time-domain electric field integral equation (TD-EFIE) based on surface equivalence theorem. The scattered field formulation enables us to reduce computation cost effectively for the case that scatterers are located at a far distance from field sources of electromagnetic wave since we need to calculate the scattered field component only on the region in the vicinity of the scatterers. Then it is required for the use of the scattered field formulation that the field source for the incident field component has to be expressed by any analytical solutions such as a point dipole source, plane wave, and so on. In this work, the scattered field formulation of the FDTD method is applied to cases that there are no analytical expressions of the field sources, in which the field source contains conductors such as antennas, combining with the TD-EFIE on a virtual surface which encloses the field sources. Then, it is known that calculation of the TD-EFIE itself is time consuming. This paper considers speed-up of the S-FDTD simulation based on the TD-EFIE using a spherical harmonic expansion of Green’s function of Helmholtz equation, additionally.

Comparison of Plane Wave and Spherical Vector Wave Channel Modeling for Characterizing Non-Specular Rough-Surface Wave Scattering

This letter demonstrates advantages of modeling the nonspecular wave scattering from surfaces of a multiple-input multiple-output (MIMO) channel in terms of the spherical vector wave (SVW) mode expansion. We propose the SVW mode coupling matrix $\boldsymbol {M}$ as a more efficient alternative to the commonly used set of distinct plane waves. $\boldsymbol {M}$ incorporates the scattered field components through the limited number of modes due to the cutoff property. A planar surface with random roughness is used to simulate the nonspecular scattering contribution to the radio channel, which is computed using physical optics. The matrix $\boldsymbol {M}$ and the plane wave channel model parameters are estimated from simulated radio channels. The estimates are used to compare the contribution of the nonspecular scattering to the radio channel reproduced from these two approaches. The comparison is performed for a small array antenna arrangement. Compared are the error of the magnitudes of MIMO channel transfer matrix, the narrowband channel eigenvalues, the correlation matrix distance, and the mutual information. It is found that $\boldsymbol {M}$ from the SVW channel modeling performs better in reproducing the radio channel of nonspecular scattering from the studied rough surface.

Scattering of Lommel beams by homogenous spherical particle in generalized Lorenz–Mie theory

In this paper, we investigate the generalized Lorenz–Mie theory (GLMT) for calculating the scattered field components of Lommel beams by a homogenous spherical particle. We use also, the integral localized approximation for computing the beams shape coefficients for this kind of beams. These coefficients are of great interest in the description of beams in the GLMT but valuable only if the axicon angle is small enough. This work is devoted to the study the far field scattered intensity by homogenous dielectric spherical particle illuminated by x-linearly Lommel beams. All through this work, the effects of various parameters characterizing the feature of Lommel beams on the scattered intensity are analysed numerically.

Effects of ferrite coating layer on PEMC sphere radar cross section

Characteristics of Radar Cross Sections (RCS) in the presence of ferrite coating layer on perfect electromagnetic conductor sphere have been studied theoretically and analytically. Spherical wave vector functions were used to expand the incident, scattered and transmitted electromagnetic field components. Co and Cross polarized scattered field components have been evaluated by applying PEMC boundary conditions at both interfaces, i.e., free space- ferrite layer and at ferrite layer-PEMC sphere core. By using obtained values of the Co and Cross polarized scattering coefficients, the forward and backscattered Radar Cross Section were calculated and compared with already published literature. The effects of applied dc bias magnetic field, saturation magnetization, incident frequency, sphere radius and relative permittivity on forward and backscattered radar cross section were analyzed in graphical form.

Light scattering in a medium with fluctuating gyrotropy: Application to spin-noise spectroscopy

The spin noise signal in the Faraday-rotation-based detection technique can be considered equally correctly either as a manifestation of the spin-flip Raman effect or as a result of light scattering in the medium with fluctuating gyrotropy. In this paper, we present rigorous description of the signal formation process upon heterodyning of the field scattered due to fluctuating gyrotropy. Along with conventional single-beam experimental arrangement, we consider here a more complicated, but more informative, two-beam configuration that implies the use of an auxiliary light beam passing through the same scattering volume and delivering additional scattered field to the detector. We show that the signal in the spin noise spectroscopy arising due to heterodyning of the scattered field is formed only by the scattered field components whose wave vectors coincide with those of the probe beam. Therefore, in principle, the detected signal in spin noise spectroscopy can be increased by increasing overlap of the two fields in the momentum space. We also show that, in the two-beam geometry, contribution of the auxiliary (tilted) beam to the detected signal is represented by Fourier transform of the gyrotropy relief at the difference of two wave vectors. This effect can be used to study spin correlations by means of noise spectroscopy.

Propagation of Radio and Microwave Frequency Electromagnetic Pulses in Dielectric and Magnetic Dispersive Media

Analysis of the propagation and attenuation of electromagnetic (EM) waves and of the dispersive properties of the dielectric permittivity and of the magnetic permeability of a propagating medium deals with the concept of signal velocity in electromagnetism, specially to differentiate free-space light velocity from phase velocity in a given medium. The analysis is important for several technical applications, which employ EM energy in the radio frequency and microwave bands, such as: ground probe radar, material science, and bioelectromagnetism. This paper investigates the propagation of a sine wave pulse lasting one period within those frequency bands, to describe and quantify the behavior of primary signals in dispersive media relying on Lorentz models. The results show that a careful analysis allows to identify dielectric and magnetic dispersive media and to distinguish them from hypothetical nondispersive conductive media. So, it will help to separate primary fields from the scattered field components in actual surveys, what will improve interpretation. Therefore, it may increase the accuracy of the determination of the physical properties of the investigated medium.

A Generalized case of Electromagnetic Scattering from a finite number of Ferromagnetic cylinders

A generalized solution of the scattering problem from an array containing a finite number of axially magnetized ferromagnetic cylinders of infinite length placed in free space is presented in this paper. The analysis is carried out by matching the tangential boundary conditions at the surface of each cylinder to find the unknown expansion coefficients of the scattered field. Planar arrays consist of a finite number of ferromagnetic microwires are considered to obtain the numerical results for TMz and TEz polarizations in terms of the variation in scattered field components of the near field and scattering cross section (SCS) with respect to angle of incidence, radius of microwires, spacing among the microwires and operating frequency. For validation purpose, numerical results of the proposed analysis specialized for the case of single microwire and normal incidence for TMz polarization are compared with the results available in the literature for the specialized case and both are found to be matched completely.

A generalized case of the electromagnetic scattering from an array of ferrite cylinders

A boundary value type solution of the generalized case of scattering from an array consisting of a finite number of axially magnetized ferromagnetic circular cylinders is presented in this paper. Proposed analysis is carried out by matching the tangential fields at the surface of each cylinder to find the unknown expansion coefficients of the scattered field. A planar array having size and a linear array having size consist of ferromagnetic microwires are considered to obtain the numerical results for and polarizations in terms of the variation in scattered field components of the near field and scattering cross section with respect to the angle of incidence, radius of microwires, spacing among the microwires, number of microwires in the array, and operating frequency. For validation, theoretical results of the method already available in the literature are simulated for a linear array and compared to match with the numerical results of proposed analysis for the same array. In order to prove the generalization of the solution in terms of the number of microwires, simulated results specialized to the case of single ferromagnetic microwire are shown to be matched with the results available in the literature for the special case.

Electromagnetic Inverse Scattering of Axially Moving Cylindrical Targets

Electromagnetic inverse scattering techniques are considered to reconstruct the permittivity and the velocity profiles of axially moving cylindrical targets. Two approaches are proposed. One of these is based on a two-step procedure. It is shown that it provides good approximations of the profiles to be reconstructed in a very efficient way, when the peak velocity is small with respect to the speed of light in vacuum. These features are obtained by neglecting the movement in the first step, which is devoted to the reconstruction of the geometric and dielectric properties of the cylindrical targets. The second approach is more classical and is defined as a global optimization problem. It is shown that the two procedures are in some way complementary in the sense that, when the two-step procedure can be applied, it is by far the best, with the general procedure giving large errors; vice versa, the two-step procedure is in trouble when the other one gives good results. In carrying out this analysis, some estimates on the effects of the movement on the scattered field components are deduced in the limit as the peak velocity goes to zero.

A comprehensive examination of the acoustic vector fields scattered by cylindrical bodies

In this study, the properties of the scattered acoustic vector fields generated by infinite-length and finite-length rigid and elastic cylinders are investigated. Analytical solutions are derived from general acoustic pressure scattering models, and analyzed for wave numbers in the resonance region. The separable active and reactive components of the acoustic intensity are used to investigate the structural features of the scattered field components. Numerical results are presented for the near field and transition regions. A finite element model is developed for both rigid and elastic cylindrical bodies. The finite cylinder model and analysis is then extended to include interactions with an elastic half space. The vector properties of the time-independent complex intensity components and their relations to field energy density quantities are summarized.

Three-Dimensional Microwave Holographic Imaging Using Co- and Cross-Polarized Data

A full vector three-dimensional holographic technique is proposed for near-field imaging of dielectric bodies. This new formulation allows for the processing of two (co- and cross-polarized) scattered field components in a single reconstruction process. We demonstrate that employing both co- and cross-polarized signals leads to significant improvement of the target shape reconstruction. The simulated examples for X-shaped and square-shaped targets in a lossy background medium are presented.

Electromagnetic fields near plasmonic wedges

The behavior of electromagnetic fields near the edge of a plasmonic wedge is investigated. We study the scattering properties, field divergence, and field enhancement near an Au wedge bounded by SiO2 upon illumination by TM-polarized light using hypersingular integral equations, as a function of wavelength, wedge angle, and angle of incidence. The transverse scattered field components show a convergent behavior at wavelengths approaching the surface plasmon energy asymptote (on the corresponding flat Au-SiO2 interface), and become strongly divergent at longer wavelengths. The computed divergence is compared with Meixner's theory and is found to be in good agreement over a restricted range of parameters.

Characterization of scattered acoustic intensity fields of finite cylinders in the resonance region

The properties of the scattered acoustic vector fields generated by infinite-length and finite rigid and elastic cylinders are investigated. Analytical solutions are derived from general acoustic pressure scattering models and analyzed for wave numbers in the resonance region. The separable active and reactive components of the acoustic intensity are used to investigate the structural features of the scattered field components. Numerical results are presented for the near and transition regions. A finite element model is developed for a rigid cylinder and compared to measured results in-air using an anechoic chamber and acoustic vector sensor probes to measure the scattered acoustic vector field. The finite cylinder model and analysis is then extended to include an evacuated thin-walled elastic shell. The vector properties of the time-independent complex intensity components and their relations to field energy density quantities are summarized.

A characterization of the scattered acoustic intensity field in the resonance region for simple spheres

The properties of the scattered acoustic vector fields generated by simple spheres illuminated by monotonic continuous wave (CW) plane waves are investigated. Analytical solutions are derived from general acoustic pressure scattering models and analyzed for wave numbers in the resonance region. Of particular interest is the understanding of the characteristics of the scattered acoustic vector field in the near-to-far-field transition region. The separable active and reactive components of the acoustic intensity are used to investigate the structural features of the scattered field components. Numerical results are presented for the near and transition regions for a rigid sphere. A method of mapping nulls in the scattered intensity field components is described. The analysis is then extended to include a simple fluid-filled boundary and finally the evacuated thin-walled shell. Near field acoustic intensity field structures are compared against mechanical material properties of vacuous shells. The ability to extract scattered field features is illustrated with measurements obtained from a recent in-air experiment using an anechoic chamber and acoustic vector sensor probes to measure the scattered acoustic vector field from rigid spheres.

Scattering in a Pekeris waveguide from a rough bottom using a two-way coupled mode approach

Scattering from a rough ocean bottom is described numerically with a two-way coupled-mode formalism that contains scattering effects to all orders and provides an exact solution to the wave equation. Both scattered field and direct blast components are computed within the formalism framework. A comparison of the scattered component solution from the coupled mode with the Born approximation (BA) solution for scattering from a rough bottom Pekeris waveguide shows that the BA predicts correctly the scattered field levels but not detailed structure. The transition from direct blast to scattered field dominance is identified in the total field time series.

Scattering in a Pekeris waveguide from a rough bottom using a two-way coupled mode approach.

Scattering from a rough surface is described numerically with a two-way coupled-mode formalism that contains scattering effects to all orders and provides, in principle, an exact solution to the wave equation. Both scattered field and direct blast components are computed within the framework of the formalism. In contrast to finite elements, each modal component can be calculated separately. A comparison between the scattered component from the coupled mode and Born approximation solutions is presented for scattering from a rough bottom Pekeris waveguide. Total field time series are constructed, and the transition from direct blast to scattered field dominance is identified. For a Gaussian source pulse, the frequency band needed to resolve the scattered component is shown to be much less than is required to resolve the direct blast. Convergence tests to validate the accuracy of the solution are discussed. The importance of the nonlinear contributions to the scattering is identified. The usual method of time averaging the solution produces lower intensity levels than those obtained from the envelope of the time series.