This contribution concerns the interaction of an arbitrarily orientated, time-harmonic, magnetic dipole with a perfectly conducting sphere embedded in a homogeneous conductive medium. A rigorous low-frequency expansion of the electromagnetic field in positive integral powers (jk)ⁿ, k complex wavenumber of the exterior medium, is constructed. The first n = 0 vector coefficient (static or Rayleigh) of the magnetic field is already available, so emphasis is on the calculation of the next two nontrivial vector coefficients (at n = 2 and at n = 3) of the magnetic field. Those are found in closed form from exact solutions of coupled (at n = 2, to the one at n = 0) or uncoupled (at n = 3) vector Laplace equations. They are given in compact fashion, as infinite series expansions of vector spherical harmonics with scalar coefficients (for n = 2). The good accuracy of both in-phase (the real part) and quadrature (the imaginary part) vector components of the diffusive magnetic field are illustrated by numerical computations in a realistic case of mineral exploration of the Earth by inductive means. This canonical representation, not available yet in the literature to this time (beyond the static term), may apply to other practical cases than this one in geoelectromagnetics, whilst it adds useful reference results to the already ample library of scattering by simple shapes using analytical methods.

The electromagnetic scattering from a 2D chiral circular cylinders, illuminated by either a TE_z or a TM_z plane wave, is investigated using an iterative scattering procedure. The developed formulation and the implemented code simulate different types of cylinders, where the cylinders can be made of anisotropic chiral material with uniform or non-uniform chiral admittance distribution, homogeneous isotropic dielectric material, perfectly conducting material or a combination of all of them. The technique applies the boundary conditions on the surface of each cylinder in an iterative procedure in order to solve for the field expansion coefficients. Numerical verifications are presented to prove the validity of the formulation before presenting the scattering from an array of chiral cylinders showing significant RCS reduction in forward or backward directions based on the selection of the chirality parameter.

Helix particle exhibits uniaxial electrical-magnetic coupling and doped material with helix particles has the nonlinearity properties of electromagnetic waves. Based on the small nonlinearity assumption, nonlinear electromagnetic waves propagating in doped materials with transversely and longitudinally uniaxial electrical-magnetic coupling are analytically formulated, respectively. It is shown that this class of nonlinear material can simultaneously support right- and left-handed elliptically-polarized nonlinear waves. In the case of transversely uniaxial electrical-magnetic coupling, the two nonlinear waves propagate with different phase velocities (sub- and super-luminously, respectively) and spatial profiles. For the case of longitudinally uniaxial electrical-magnetic coupling, the two nonlinear waves exhibit different spatial profiles but propagate with the same phase velocity. It is also found that complex nonlinear waves, which propagate with complex phase factor, could exist for certain constitutive parameters of this class of nonlinear material.

The generalized system function, H(s), directly associated with the radiated or scattered fields is presented in this paper, which is constructed by applying the model-based parameter estimation (MBPE) technique combined with the complex frequency theory. A complex frequency ω̃ relating the real resonant frequency with radiated or scattered Q factor is introduced to antenna and scattering systems. By analyzing the characteristics of complex poles and zeros of H(s) in a finite operational frequency band, and combining with adaptability of MBPE, we can determine the resonant frequency and Q-value of the antenna and scattering systems effectively. The intensity of resonance can be estimated in terms of Q-value and residues at the complex resonant frequencies. Some examples of the practical antenna arrays and scattering systems are given to illustrate the application and validity of the proposed approach in this paper.

This paper presents the adaptive integral method (AIM) utilized to solve scattering problem of mixed dielectric/conducting objects. The scattering problem is formulated using the Poggio-Miller- Chang-Harrington-Wu-Tsai (PMCHWT) formulation and the electric field integral equation approach for the dielectric and conducting bodies, respectively. The integral equations solved using these approaches can eliminate the interior resonance of dielectric bodies and produce accurate results. The method of moments (MoM) is applied to discretize the integral equations and the resultant matrix system is solved by an iterative solver. The AIM is used then to reduce the memory requirement for storage and to speed up the matrix-vector multiplication in the iterative solver. Numerical results are finally presented to demonstrate the accuracy and efficiency of the technique.

Achieving a high stability of the phase centre position in horn antennas with respect to frequency is a very desirable aim in reflector antenna design; a highly stable phase centre reduces efficiency dropping for defocusing at the frequency band extremes. By using an appropriate profile for the horn antenna it is possible to obtain horns both compact and with a stable phase centre. In this paper an automatic design procedure, based on Genetic Algorithms, to obtain such horns is described. The algorithm operates on many horn profile parameters, including corrugations, and is based on an accurate fullwave mode matching/combined field integral equation analysis code. To keep computing time down a full parallel algorithm over a 12 CPU parallel virtual machine is described.

A system consisting of a smart antenna and a processor can perform filtering in both the time and space domain,th us reducing the sensitivity of the receiver to interfering directional noise sources. Smart antennas can be used for further increase in the capacity of a communication system and for variable speed of transmission for multimedia information. Switched beam antenna arrays are a subset of smart antennas that cover either the x-y plane or a portion of it with multiple radiation patterns. A processor can decide which pattern to use for reception or transmission. In this paper the use of genetic algorithms (GAs) is examined in the design of switched beam antenna arrays. The antenna consists of five or six elements and the radiation patterns vary from 4 to 8, covering the x-y plane with the main beams of the radiation patterns pointing at 0°, 90°, 180°, 270° and 0°, 45°, 90°, 135°, 180°, 225°, 270°, 315° respectively. The positions of the antenna elements are either chosen exclusively by the GA or are assumed to form a circular array with one central element and the GA decides for the radius and the offset angle of the circle. Furthermore, the GA is asked to design an array covering the first 120° of the x-y plane with 4 radiation patterns pointing at 15°, 45°, 75° and 105°. Such a configuration can be used in sector antennas,whic h are widely used in 2G mobile communication systems.

The approach based on investigation of characteristic properties of the resolving operators (resolvents) of stationary boundary value problems of the theory of wave diffraction by gratings is used for the analysis of the basic regularities running the formation of resonant non-stationary scattered fields. Information about singularities provides the description of the anomalous effects connected with possibility of existence, in the structures under consideration, of eigen modes having super high Q-factor, with linear "interaction" of modes in the parameter regions of spectrum crowding.

The electric field integral equation (EFIE) with the method of moments (MoM) is used for treating problems of a thin wire antenna in the presence of a conducting cube. Pulse-expansion and point-matching technique in MoM are applied to both thin wire and closed object. For simplicity and efficiency, hybrid method for calculating near field and more importantly the surface field of objects is presented. Several examples in this paper show the validity of the proposed pulse-expansion and point-matching technique and the simplified hybrid calculation method.

In this paper, we analyze the transient electromagnetic response from three-dimensional (3-D) dielectric bodies using a time domain PMCHW (Poggio, Miller, Chang, Harrington, Wu) integral equation. The solution method in this paper is based on the Galerkin's method that involves separate spatial and temporal testing procedures. Triangular patch basis functions are used for spatial expansion and testing functions for arbitrarily shaped 3-D dielectric structures. The time domain unknown coefficients of the equivalent electric and magnetic currents are approximated by a set of orthonormal basis functions that are derived from the Laguerre functions. These basis functions are also used as the temporal testing. Use of the Laguerre polynomials as expansion functions characterizing the time variable enables one to handle the time derivative terms in the integral equation and decouples the space-time continuum in an analytic fashion. We also propose an alternative formulation using a differential form of time domain PMCHW equation with a different expansion for the equivalent currents. Numerical results computed by the two proposed methods are presented and compared.

The variational closed-forms of the capacitance formulae of a type of conformal coaxial lines are presented in this paper with the assumption that the equipotential lines are conformal to the contour of the coaxial line. The variational extreme formula of the functional of continuous functions is first obtained. Then the variational stable and analytical expression of the capacitance is deduced. Considering the actual applications, we give the variational stable formulae of the capacitances of the conformal coaxial transmission lines whose contours are homogeneous curves of the 1st, 2nd and n-th order. Examples are given including the conformal regular polygonal, elliptical and highorder elliptical coaxial lines.

In this paper,the design idea and technique of the ferrite phase shifter in substrate integrated waveguide (SIW) has been reported. The characteristics of the millimeter-wave ferrite phase shifter have been firstly calculated analytically,and the relative parameters of the device have been decided on the basis of optimization. At the same time,the design procedure of transition from ferrite phase shifter in SIW to CPW has been introduced; the agreement between the simulation results of the final integrated structure and the experimental results of an equivalent model has shown the good performance of this integrated structure.

In this paper, the modal method is applied to analyze coated circular waveguide terminated by a perfect electric conductor (PEC) plate. The key to this method is the accurate calculation of the propagation constants of modes in coated circular waveguide. To overcome numerical difficulties, such as overflow, encountered in solving characteristic equation, the characteristic equation is modified using Hankel function of the second kind instead of Bessel function of the first kind in the coated layers. The modified characteristic equation can be accurately solved to obtain the propagation constants even for very large circular waveguide with highly lossy coatings. To verify the modified characteristic equation, the attenuation and scattering property of circular waveguide structure have been simulated. Simulation results agree well with the reference results.

In this paper is presenteda methodfor computing, andan experimental procedure for verifying, the coupling of a signal, caused by a modulatedlaser beam, to a loadimp edance terminating a coaxial waveguide whose center conductor protrudes into a an open-ended body of revolution (BOR). The excitation is the signal radiated by electrons emittedfrom the conducting surface by an impinging laser beam, modulated in such a way that the electrons escaping the surface oscillate harmonically in time causing them to radiate a coherent signal at an angular frequency ω. For a vanishingly small spot of laser light on the conducting surface, the radiating source is modeled as an electric dipole normal to and located at the surface. To perform this computation directly is very difficult so we resort to an indirect methodthat allows us to realize significant savings with no loss in generality. The indirect approach adopted here takes the advantage of the reciprocity andallo ws one to determine the receivedsignal at the coax terminal load from knowledge of the field radiated by a small wire probe mounted on the symmetry axis of the BOR under the condition that the excitation results from a current generator impressedat the terminal endof the coax. This scheme necessitates the formulation andsolution of a simpler integral equation. In principle, the approach developed to solve this problem is exact and rigorous. The validity of this approach is demonstrated numerically and experimentally.

In this work,the ray trajectory for oblique incidence is determined by solving the wave equation using the Finite Element Method (FEM). In case of ionospheric reflection the Discrete Fourier Transform (DFT), applied here in the space domain, is used to discriminate the incident and reflected waves. Ray tracing equations are combined with the Poynting vector components in order to calculate the wave trajectory taking into account the Earth's curvature. The results are illustrated for different frequencies and angles of incidence using electron density profiles obtained from the Rome digisonde station,topside profiles from the IRI-95 model and atmospheric data from the MSIS-E-90 model of NSSDC as an inputs.

A new procedure for fast computing mixed potential spatial domain Green's functions for cylindrically stratified media is developed in this paper. Based on the fundamental behaviour of electric field Green's functions, spectral domain Green's functions for mixed potential integral equation (MPIE) are formulated by decomposing electric field Green's functions into appropriate forms. The spatial domain mixed potential Green's functions are obtained by using inverse Fourier transform applied to the spectral domain Green's functions. The summations of infinite cylindrical harmonics are accelerated by subtracting a term to resolve the problem of the series' slow convergence and by using the Shank's transform. The Sommerfeld integrals are efficiently evaluated using the discrete complex image method (DCIM) and the generalized pencil of function (GPOF) technique.

Recently non-relativistic boundary conditions, based on the Lorentz force formulas, have been investigated. It was shown that to the first order in the relative velocity v/c the results for scattering problems are in agreement with the exact relativistic formalism. Examples for scattering by material objects moving in free space have been discussed. Presently the feasibility of non-relativistically solving scattering problems involving arbitrary material media is investigated. For concreteness, two representative canonical problems were chosen: scattering by a uniformly moving circular cylinder, and the related problem of a cylinder at rest, comprised of a uniformly moving medium in the cylindrical cross-sectional plane. The investigation demonstrates that solving such problems is feasible, and indicates the complexity involved in such an analysis. The main highlights are that we need to evaluate the phases and amplitudes of waves at the scatterer's surface, employing formulas based on the Lorentz force formulas and the Fresnel drag concept. The explicit solutions for the scattering problem display velocity-dependent interaction of the scattering coefficients.

Abstract-Performance trends varying with different geometrical parameters for on-chip spiral inductors: (a) with fixed inner-dimension, (b) with outer-dimension, and (c) variation in both inner- and outerdimensions are extensively investigated in this paper. The relationships for the inductance, Q-factor and self-resonance frequency (SRF) with various geometrical parameters, such as track width, track spacing, and turn numbers are examined on an extensive experiment basis. These performance trends can be a good guideline for practical inductor designs in RFICs.

Abstract-In this paper, the region of interest consists of the spherical dielectric earth, coated with a dielectric layer under the air. The simple explicit formulas have been derived for the electromagnetic fields of a vertical electric dipole and vertical magnetic dipole in the presence of three-layered spherical region, respectively. Next, basing on the above results, the formulas for the six components of the field in the air generated by a horizontal electric dipole are derived by using reciprocity. The computations show that the trapped surface wave of electric type can be excited efficiently and the trapped surface wave of magnetic type can not be excited when the thickness l of the dielectric layer is somewhat and satisfies the condition 0 < √(k²₁-k²₀)*l < Ï€/2.When the thickness l of the dielectric layer is somewhat and satisfies the condition Ï€/2 < √(k²₁-k²₀)*l < Ï€, the trapped surface wave of magnetic type can be excited. These formulas and the computations can be applied to the surface communications at the lower frequencies.

The plane wave diffraction by a terminated semi infinite parallel-plate waveguide with two-layer material loading and impedance boundaries is rigorously analyzed for E polarization using the Wiener-Hopf technique. Introducing the Fourier transform for the scattered field and applying boundary conditions in the transform domain, the problem is formulated in terms of the simultaneous Wiener-Hopf equations, which are solved via the factorization and decomposition procedure. The scattered field is evaluated by taking the inverse Fourier transform and applying the saddle point method. The numerical examples of the radar cross section (RCS) are represented for various physical parameters and backscattering characteristics, of considered geometry for open ended cavity and discussed in detail.