Some insights on the short pulse scattering from a small target. Case study: The PEC sphere revisited (original) (raw)
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Statistical electromagnetic analysis of PEC sphere scattering
2014 4th International Conference on Engineering Technology and Technopreneuship (ICE2T), 2014
This paper presents the far field scattering properties of a perfect electric conductor (PEC) sphere from the statistical electromagnetics (SEM) point of view. The probability distribution function (PDF) of the calibration error for both monostatic and bistatic radar cross section (RCS) has been discussed. Closed form expressions for the monostatic RCS in the Rayleigh region and optical region have been derived. Monte Carlo simulations have been performed for general cases. The results show that, with a given alignment uncertainty the calibration uncertainly can be determined without/before apply practical measurement, and vice versa; the calibration uncertainty obtained here can be regarded as the theoretical limit that cannot be exceeded in practice.
Unveiling the scattering behavior of small spheres
Physical Review B, 2016
A classical way for exploring the scattering behavior of a small sphere is to approximate Mie coefficients with a Taylor series expansion. This ansatz delivered a plethora of insightful results, mostly for small spheres supporting electric localized plasmonic resonances. However, many scattering aspects are still uncharted, especially with regards to magnetic resonances. Here, an alternative system ansatz is proposed based on the Padé approximants for the Mie coefficients. The results reveal the existence of a self-regulating radiative damping mechanism for the first magnetic resonance and new general resonating aspects for the higher order multipoles. Hence, a systematic way of exploring the scattering response is introduced, sharpening our understanding about the sphere's scattering behavior and its emergent functionalities.
The Impedance Scattering Problem for a Point-Source Field. The Small Resistive Sphere
The Quarterly Journal of Mechanics and Applied Mathematics, 1997
A small resistive scatterer disturbs a spherical time-harmonic field emanating from a point source. The incident point-source field is normalized in such a way as to be able to recover the corresponding results for plane-wave incidence. The full low-frequency expansion for the corresponding total field is reduced to an exterior boundary-value problem for the Laplace equation, which has to be solved repeatedly. Exact results for the case of a small resistive sphere are obtained. It is shown that the leading low-frequency approximations for the scattering as well as for the absorption cross-section are increasing functions of the impedance parameter and decreasing functions of the distance of the source from the scatterer. It is also shown that a small sphere scatters and absorbs more energy when it is illuminated by a point-rather than by a plane-wave field establishing the fact that the closer the source of illumination to the scatterer, the stronger the interaction. The leading approximation of.the absorption cross-section is independent of the wavenumber, while the leading approximation of the scattering cross-section is proportional to the second power of the wavenumber. Hence, in the low-frequency realm, absorption is by two orders of magnitude stronger than scattering. Finally, a comparison between point-and plane-wave incidence, based on multipole expansions, is included.
IDENTIFICATION OF RADAR TARGETS IN RESONANCE ZONE: E-PULSE TECHNIQUES - Abstract
Journal of Electromagnetic Waves and Applications, 2003
Radar scattering amplitudes contain pole singularities whose importance was recognized in the context of the Singularity Expansion Method: S.E.M. This method uses the fact that the late time domain response r t (t) of a target, illuminated by an E.M. wave, is mainly defined in a frequency band corresponding to the resonance region of the object. The knowledge of the singularities is useful information for discrimination of radar targets and has been used for different purposes of discrimination and identification. In this paper, we propose a modified scheme of radar target identification. The method presented is based on E-Pulse technique. In practical cases, direct application of classical E-Pulse techniques is not very efficient. Its performances are damaged by the characteristics of the exciting signal (antenna output signal). We propose a modified scheme of E-Pulse technique, which allows more accurate target discrimination and improves radar target identification. This procedure requires the deconvolution of the target response by the antenna signal and the application of an equivalent gaussian impulse excitation. This process has been successfully tested to FDTD simulations and measurements in anechoic chamber.
2020
If the duration of the input pulse resonantly interacting with a system is comparable or smaller than the time required for the system to achieve the steady state, transient effects become important. For complex systems, a quantitative description of these effects may be a very difficult problem. We suggest a simple tractable model to describe these phenomena. The model is based on approximation of the actual Fourier spectrum of the system by that composed of the superposition of the spectra of uncoupled harmonic oscillators (normal modes). The physical nature of the underlying system is employed to select the proper approximation. This reduces the dynamics of the system to tractable dynamics of just a few driven oscillators. The method is simple and may be applied to many types of resonances. As an illustration, the approach is employed to describe the sharp intensive spikes observed in the recent numerical simulation of short light pulses scattered by a cylinder in the proximity o...
HIGH FREQUENCY SCATTERING BY AN IMPENETRABLE SPHERE
Progress In Electromagnetics Research, 2009
The high frequency scattering of a scalar plane wave from an impenetrable sphere with a diameter of several thousand wavelengths is treated by the Sommerfeld-Watson transformation, the saddle-point technique (SPT), and the numerical steepest descent method (NSDM). Both the near and far fields for the sphere are computed within the observation angle range of 0 to 180 degree. First, with the aid of the Watson transformation, the fast-convergent residue series replacing the slow-convergent Mie series is derived. Second, a new algorithm for finding the zeros of the Hankel functions is developed. Third, a novel NSDM, which is adaptive to frequency and is hence frequency independent, is proposed to overcome the breakdown of the traditional SPT in the transition region. Numerical results show that when the observation angle is very small, the Mie series solution of the near-field will not be accurate due to error accumulation. Furthermore, using the proposed methods, the CPU times for both the near-field and far-field calculations are frequency independent with controllable error. This work can be used to benchmark future works for high-frequency scattering.
Scattering of a Spherical Gaussian Pulse Near an Absorbing Half Plane
The space±time acoustic wave diraction due to a spherical Gaussian pulse near an absorbing half plane introducing the Kutta±Joukowski condition (wake condition) is considered. The temporal Fourier transform is used to calculate the diracted ®eld. It is found that the ®eld produced by the Kutta±Joukowski condition will be substantially in excess of that in its absence when the source is near the edge. #
Subsurface Target Recognition Based on Transient Electromagnetic Scattering
The E-pulse technique which typically uses transient scattering data from radar targets in free space is one of the most well known resonance based radar target recognition schemes on which target recognition is based. In this communication, the possibility of subsurface target recognition based on the E-pulse technique is investigated using numerical examples of a metallic hip prosthesis embedded in models of realistic human tissue.