The analysis of electromagnetic scattering from cavity structure is very important to many practical applications. The field iterative method (FIM) is one of the promising methods to deal with the cavity problem. In this paper, 3-dimensional (3D) FIM has been implemented using Rao-Wilton-Glisson (RWG) basis function and an accurate equivalent model of the cavity. Two testing procedures, a newly developed point matching and conventional Galerkin's methods, have been discussed for better and simpler implementation of the 3D FIM. Numerical results show that the accuracy of the 3D implementation of FIM using the newly developed point matching method is the same as that of the conventional Galerkin's method. The numerical results also show that the simpler implementation of 3D FIM using the point matching method converges very fast for all the tested cases.

A full-wave evaluation of the electromagnetic field in conformal structures with linear loading materials is presented in this paper. The analysis is performed considering at first conformal components with conventional isotropic and homogeneous media in the generalized orthogonal curvilinear reference system. In this first case, a summary of the possible analytical solutions of the vector wave equation obtainable through various factorization techniques is given. Then, the attention is focused on conformal structures involving non-conventional media (anisotropic, chiral, bianisotropic) and in this case the field solution is demanded to a new generalization of the transmission line approach. As an aside, exploiting a contravariant field formulation, which allows writing Maxwell's equations in the generalized reference system as in the Cartesian one, a useful relationship between the local curvature of the geometry and a suitable inhomogeneity of a related planar structure is presented. Finally, some results, obtained simulating the behavior of patch radiators mounted on curved bodies through the combined application of an extended Method of Line (MoL) numerical algorithm and the theoretical approach here derived, are presented.

We develop in this paper a theoretical approach to describe the electrodynamics of carbon nanotubes (CNTs). A lattice dynamics formalism is employed to model the mechanical response of matter to the radiation field. We start first by deriving the normal modes of the free lattice. Then, a simple and general microscopic model for light-matter interaction is proposed and the resulting mechanical equation of motion is derived using a suitable Lagrangian formalism. The symmetry group of the CNT is employed to explicitly probe the nonlocal structure of the fields and to carefully insure that higher-order Floquet modes are included in the derivation. The normal modes are then employed to perform an eigenmode expansion for the solution of the mechanical equation of motion, leading to the susceptibility tensor of the CNT medium. The final expression of this tensor describes the electrodynamics in the CNT viewed as a low-dimensional surface and is shown to be reduced effectively to a one-dimensional response function.

Circularly polarized superquadric dielectric resonator antenna is investigated. A single coaxial probe is used to excite circularly polarized patterns. Finite element method is used to analyze the problem. Different aspect ratios of the superquadric dielectric resonator cross section for each squareness parameter for circular polarization are calculated.

An approach utilizing a paraboloid photonic crystal structure (PPCS) is proposed in this paper to compensate the polarization discrimination of an antenna's radiation. It is demonstrated by considering a reflector antenna excited by a pair of crossed-dipoles, whose circularly polarized (CP) radiation may be distorted due to the scattering from the finite reflector surface. The proposed approach tends to compensate the discrimination and achieve a wider beamwidth of good axial ratios while, in the mean time, retaining a less gain loss. The advantage of this approach is that the PPCS can be integrated into a radome structure of the antenna without increasing an excess cost. Numerical studies are conducted in this paper and demonstrate that this compensation method can achieve a beamwidth of about 30 degrees at the frequency of 12.45 GHz.

Fields inside the chiral nihility slab which is backed by perfect electric conductor are determined. It is noted that both electric and magnetic fields exist inside the grounded chiral nihility slab when it is excited by a plane wave. Electric field inside the slab disappears for excitation due to an electric line source. Magnetic field inside the slab disappears when geometry changes to corresponding dual geometry. Dual geometry means chiral nihility slab backed by perfect magnetic conductor and excited by a magnetic line source. Using fractional curl operator, fields are determined for fractional order geometries which may be regarded as intermediate step between the two geometries which are related through principle of duality. Discussion is extended for chiral nihility slab which is backed by perfect electromagnetic conductor (PEMC).

This paper presents a comprehensive Non Line of Sight (NLOS) localization scheme in a multipath environment where the scatterers with smooth surfaces are aligned parallel or perpendicular to each other. It leverages on the estimation of Angle of Arrival (AOA) and Time of Arrival (TOA) of the omni-directional mobile device's signal received at the reference devices. Unlike the conventional Line of Sight (LOS) localization schemes that rely on the various mitigation techniques to mitigate the multipaths that are mistaken as the LOS signal, our proposed two step localization scheme not only utilizes the LOS path but also any one bound scattering NLOS multipath arriving at the reference devices for localization. Channel experiment coupled with simulation results in a typical multipath environment has demonstrated that our proposed localization scheme outperforms the conventional localization schemes that are coupled with their own mitigation techniques. Robustness in performance of our proposed localization scheme towards different scatterers' orientation where they are not aligned parallel or perpendicular to each other are also investigated.

In order to simulate the electromagnetic scattering of targets with thin-coating accurately, a conformal finite-difference timedomain (CFDTD) method based on effective constitutive parameters is presented in this paper. Two kinds of coating problems are considered. For a coated target with medium backing material, the CFDTD formulations on conformal cells are the same as those of the conventional FDTD, but the parameters in FDTD formulations are replaced by effective constitutive parameters to include the curved coating message of target. For a coated target with perfectly conducting (PEC) backing material, the contour-path integral is used to exclude the curved PEC part, and effective constitutive parameters are then introduced to include the coating message. The bistatic radar cross section (RCS) of coated spheres with medium backing material and with PEC backing material are computed, respectively, to validate the presented CFDTD scheme. The backscattering of a composite airfoil, which is made of radar absorbing material (RAM) and metal framework, and coated by fiberglass-reinforced plastics, is also analyzed to demonstrate the feasibility of presented scheme.

In this paper, the edge-facet model is transformed to the Non-Uniform Rational B-Spline (NURBS) model. The parameters of the knot vectors and the control points of NURBS are computed based on the data points on the surface of a target, and the NURBS model is constructed with the parameters. The degrees of the two parametric directions of a NURBS surface and the B-spline basis function are also analyzed. The relative errors between the NURBS models and the real models prove that the modeling method proposed in this paper is exact. Finally, the results of the Radar Cross Section (RCS) computed by the Physical Optics (PO) method with NURBS models are illustrated, and the results prove that the modeling method is of high precision and can be widely used in computational electromagnetics techniques.

A dual-mode dual-band bandpass microstrip filter using double square-loop structure is proposed in this paper. Each of the square-loop forms a dual-mode resonator with controllable respective passband. Two tuning patches placed symmetrically at the side of the perturbation patch are used to change the higher passband frequency, while while keeping the lower invariable. Several attenuation poles in the stopband are realized to improve the selectivity of the proposed bandpass filter. The filter is evaluated by experiment and simulation with good agreement.

For certain applications in radio astronomy, viz. radio spectrographs, spectrum monitoring etc., only the amplitude power spectrum coverage within an angle of observation could be of interest. Ideally, the antenna structures of such instruments should illuminate this covering angle with a fixed uniform gain. This might be achieved using a combination of dipole antennas, a single vertical dipole, a loop antenna etc., but are subjected to limited bandwidth. This limitation could be overcome if many electrically-identical wideband antennas are positioned across the perimeter of a circle lying in the horizontal plane such that the antennas' adjacent half power beam angles touch each other. It has been theoretically observed that if two identical antennas are positioned at an angle with respect to one-another in such a way that their adjacent half power beam angles coincide, then if the amplitude power spectrums of the two are added, the result is effectively an amplitude power spectrum obtained from a single antenna having an uniform gain and uniform signal to noise ratio within the angle subtended by them. This angle also happens to be equal to the half power beamwidth of the individual antennas. A proper design using frequency independent antennas might possibly result to an user specified uniform amplitude power spectrum gain coverage across any required angle, with a theoretically unlimited bandwidth. More number of identical antennas might be positioned in similar fashion for extending the angular coverage. The power spectrums from these antennas could be directly added which effectively represent the power spectrum from a single antenna possessing uniform gain coverage within an angle equal to the product of individual half power beamwidth angle with one less the number of antennas, thus achieving user defined gain, wide bandwidth, and uniform signal to noise ratio across the angle. It is also possible to recover the time domain signal by applying Fourier Transform on the outputs of the antennas followed by an addition of their amplitudes while keeping the phase information identical to that of one antenna (taken as reference), and taking its inverse Fourier Transform.

In this paper,a new monopole with G type structure is proposed,consisting of two wires rectangle rings with radius of 2 mm. The software Numerical Electromagnetic Code (NEC) is used to analyze the proposed antenna and a prototype is designed. The experimental and numerical results of the designed wideband antenna are presented and analyzed,and a 510MHz bandwidth from 0.86 GHz to 1.37 GHz is demonstrated. The experimental and numerical results fit well.

In this paper, novel structures using split ring resonators (SRRs) and coupled lines are proposed and analyzed. SRRs are etched on three different planes and their propagation characteristics are compared. Two compact narrow band band-pass filters based on these structures are designed and their performances are demonstrated by simulated and measured results, which are in good agreement.

The reflectivity of a Spherical Lens Reflector is investigated. The scattering of an electromagnetic plane wave by a Spherical Lens Reflector is treated as a classical boundary value problem for Maxwell's equations. No restrictions are imposed on the electrical size of reflectors and the angular size of the metallic spherical cap. The competitiveness of the Spherical Lens Reflector against the Luneberg Lens Reflector is demonstrated. It has been found that Spherical Lens Reflectors with relative dielectric constant in the range 3.4 ≤ ε_r ≤ 3.7 possess better spectral performance than 3- or 5-layer Luneberg Lens Reflectors in a wide frequency range.

High frequency field expressions are derived around feed point of a three dimensional Cassegrain system using the Maslov's method. Maslov's method is a systematic procedure for predicting the field in the caustic region. It combines the simplicity of ray theory and generality of the transform method. Numerical computations are made for the analysis of field pattern around the caustic of a Cassegrain system.

The scattering of electromagnetic plane wave by a perfectly conducting disk is formulated rigorously in a form of the dual integral equations (abbreviated as DIE). The unknowns are the induced surface current (or magnetic field) and the tangential components of the electric field on the disk. The solution for the surface current is expanded in terms of a set of functions which satisfy Maxwell's equation for the magnetic field on the disk and the required edge condition. At this step we have used the method of the Kobayashi potential and the vector Hankel transform. Applying the pro jection solves the rest of a pair of equations. Thus the problem reduces to the matrix equations for the expansion coefficients. The matrix elements are given in terms of the infinite integrals with a single variable and these may be transformed into infinite series that are convenient for numerical computation. The numerical results are obtained for far field patterns, current densities induced on the disk, transmission coefficient through the circular aperture, and radar cross section. The results are compared with those obtained by other methods when they are available, and agreement among them is fairly well.

Based on the Mie theory, the light scattering properties of clouds consisting of pure water, pure ice spheres and concentric water- ice spheres are studied in the near-infrared regions, respectively. We computed the single scattering albedo, phase function, and asymmetry parameters of water clouds, ice clouds, and ice-water mixed clouds. The near infrared reflectivity of the ice-water mixed clouds is computed by using the adding-doubling method and compared to the other two types of clouds. It is shown that it is possible to use the near infrared reflectivity to derive the microphysical characteristics of the clouds.