In this paper, simulated annealing algorithms are applied to the analyses of nonlinearly loaded antenna arrays. The analysis is first transformed into an optimization problem and then be solved by simulated annealing algorithms. Numerical examples show that the results calculated by the proposed method are consistent with those of other published papers. Nearly global optimum solutions can be obtained since the simulated annealing algorithm is inherently a direct searching method. It should be noted that the array mutual coupling effects are included in the analyses of this paper.

An FDTD methodology is provided herein that allows for TEM excitation and detection of signals associated with N-port network analysis. The scheme is based upon the numerical solution of Laplace's equation in the context of the standard Yee grid. The invocation of both equivalence and orthogonality of modes principles assures that the TEM mode of interest is both exclusively excited and detected. Electric and magnetic surface currents are employed to render zero backward radiation from the source plane. Orthogonality is utilized at the terminal plane to extract the TEM mode from a multi-mode signal, provided that the spectrum of the guiding structure is discrete. The advantage of this approach is found in the placement of both the terminal and source planes — both can be placed as close to each other and to the network as necessary, thus alleviating the computational and memory burdens of the simulation. Examples pertaining to this methodology include stripline structures and the monopole strip antenna. The microstrip patch antenna is also considered to demonstrate the difficulties associated with the excitation and detection of quasi-TEM signals in the midst of radiation terms.

In this report one-dimensional simulation of Electromag- netic pulses reflected from moving and/or vibrating perfectly conducting surfaces is presented. The computational results are obtained through the application of the method of characteristics with the aid of the characteristic variable and the relativistic boundary conditions. The reflecting perfect surface is set to constantly travel at relatively high speed and/or sinusoidally vibrate with very high frequency in order to easily observe the relativistic effects on the reflected pulses. To validate the numerical method, the reflected electric fields and the corresponding spectra are demonstrated side-by-side for comparisons with the theoretical Doppler shift values. It is found that the computational results and the theoretical values are in good agreement.

This paper presents a coplanar waveguide fed rectangular slot antenna tuned by a patch stub. The presented antenna has 98% impedance bandwidth, and 6 dB average gain. The antenna can be used in phased array applications with more than 61% usable bandwidth.

Buried ob ject detection by means of microwave-based sensing techniques is faced in biomedical imaging, mine detection, and many other practical tasks. Whereas conventional methods used for such a problem consist in solving nonlinear integral equations, this article considers a recently proposed learning by examples approach [1] based on Support Vector Machines, the techniques that proved to be theoretically justified and effective in real world domains. The article considers the approach performance for two different kernel functions: Gaussian and polynomial. The obtained results demonstrate that using polynomial kernels along with slightly sophisticated model selection criterion allow to outperform the Gaussian kernels. Simulations have been carried out for synthetic data generated by Finite Element code and a PML technique; noisy environments are considered as well. The results obtained by means of polynomial and Gaussian kernels are presented and discussed.

A study is made of the characteristics of a perfectly conducting cylindrical antenna insulated from the surrounding cold collisionless magnetoplasma by an isotropic coaxial cylindrical sheath for the case where the antenna is aligned with an external magnetic field and is excited by means of a delta-function voltage generator. A rigorous representation is obtained for the current distribution on an infinitely long antenna. It is shown that in the whistler frequency range, the current distribution of a sufficiently thin antenna is determined mainly by the eigenmode whose guided propagation is found to be supported along the antenna. Based on the results obtained for an infinitely long antenna, a generalized transmission-line theory is developed for determining the current distribution and the input impedance of an insulated antenna of finite length located in a resonant magnetoplasma. The influence of the sheath parameters on the antenna characteristics is analyzed.

A novel coupled T-matrix and microwave network approach is proposed for the multiple scattering from parallel semicircular channels. First, an equivalent network is set up to derive the T-matrix of a single channel, in which the S-parameters are derived for the semicircular boundary and the T-matrix of the inclusive cylinders is served as loading matrix of s-parameters. In addition, the T-matrix of the inclusive cylinders is obtained from the T-matrix of each cylinder in its local coordinates using the addition theorem of cylindrical harmonics. Thus, the T-matrix description of semicircular channels could be obtained steadily by the equivalent microwave network theory. Second, the addition theorems in half space are derived and utilized to take account of multiple scattering from several parallel channels. Comparing with previous dual-series eigenfunction solutions, the coupled method simplifies the analysis and could handle much more complex structures step by step. The method is verified by comparison with previous publications and both TM and TE wave illumination are considered.

This paper describes exactly a new formulation of the T-matrix method with R-matrix expression for the electromagnetic wave diffraction efficiency from dielectric coated metallic Fourier grating. We found that the parameters of numerical calculation are widely applied by using R-matrix expression in dielectric coating media whose thickness or depth groove on the Fourier grating is large. The absorption phenomena of diffraction efficiency in particular incident angle are observed in the two cases. One of the factor is a guided mode in the dielectric coated layer. Other factor is resonance absorption that occurs by plasmon anomalies on the substrate for the TM polarization.

Electromagnetic penetration through an aperture into a cavity is considered. The structure of interest comprises a slotted infinite conducting plane backed by a semielliptical channel. Three independent integral equations are used to study the structure of interest, for which analytical expressions are derived in another paper and involve summations of Mathieu functions. Numerical results from the analytical expressions for the electromagnetic fields are compared with those from integral equation methods for various cases of excitation and isorefractive materials. The agreement is excellent in all cases.

The intra-channel collision of optical solitons, with Kerr law nonlinearity, is studied in this paper by the aid of quasi-particle theory. The perturbation terms that are considered in this paper are the nonlinear gain and saturable amplifiers along with filters. The suppression of soliton-soliton interaction, in presence of these perturbation terms, is achieved. The numerical simulations support the quasi-particle theory.

The propagation of waves in a random medium is a very complex phenomena which presents numerous difficulties in its experimental approach, and in its theoretical analysis. In this work, the case of a laser beam direction during its random propagation through a hot free jet of air, is considered using geometrical optics. Some experiments are done in the jet and from the hypothesis of the Markovian process, the main stochastic characteristics of the laser beam direction are studied. In addition, the sensitivity of the probability density of the beam random direction with respect to the jet turbulent diffusion is determined.

In this paper, a new coplanar waveguide (CPW) feed structure is proposed to improve impedance matching of low-permittivity dielectric resonator antennas (LPDRAs). The structure is studied experimentally for a two element-rectangular LPDRA array. In the proposed structure, a horizontal strip is centrally connected at the center strip of the CPW and symmetrically added to a coplanar rectangular coupled slot. The dielectric radiators are fed by the CPW through the slot. Based on the above design concept, several antenna prototypes have been successfully designed, fabricated and tested. The measured results show that the proposed antenna exhibits unique and attractive features in terms of impedance matching, gain and the realization of an array.

In a recent solution of this problem there is a subtle error that shows up in the coefficient of reflection off the lower surface of the half plane for oblique incidence and that is attributable to an unacceptable normalization of the spectra to produce the incident field. The correction of this error requires a substantial modification to the original analysis, but this has been carried out and new data are presented.

A very efficient and accurate method to characterize the electromagnetic scattering from periodic arrays of two-dimensional composite cylindrical ob jects with internal eccentric cylindrical scatterers is presented, using the lattice sums formula and the aggregate T-matrix for cylindrical structures. The method is quite general and applies to various configurations of two-dimensional periodic arrays. The dielectric host cylinder per unit cell of the array can contain two or more eccentric cylindrical scatterers (we call them inclusions in this paper), which may be dielectric, conductor, gyrotropic medium, or their mixture with different sizes. The power reflection coefficients from one-layer or one-hundred-layered periodic arrays of composite cylinders with up to two inclusions have been numerically studied. The effect of the presence of inclusions on the properties of resonance peaks or the stopband's width will be discussed.

Presently various models consistent with Einstein's Special Relativity theory are explored. Some of these models have been introduced previously, but additional models are possible, as shown here. The topsy-turvy model changes the order of postulates and conclusions of Einstein's original theory. Another model is given in the spectral domain, with the relativistic Doppler Effect formulas replacing the Lorentz transformation. In this model a new principle tantamount to the constancy of the speed of light in vacuum is stated and analyzed, dubbed as the constancy of light slowness in vacuum. Because the slowness is derived in the spectral domain from the Doppler Effect formulas, this result is not trivially semantic. It is shown that potentials and equations of continuity can replace the Maxwell Equations used by Einstein for his "Principle of Relativity" in electrodynamics. It is also shown that defining convection currents and assuming the current-charge densities transformations can replace the Lorentz transformation. The list of feasible models representative rather than exhaustive, since parts of the models presented here can be combined to yield additional models. The two underlying elements of Einstein's original Special Relativity theory are always present: (1) the theory requires a kinematical element (e.g., the constancy of the speed of light in vacuum in Einstein's original model), and (2), a dynamical element (e.g., the form-invariance of the Maxwell Equations in all inertial systems of reference in Einsteins original model).

Hypothesis of possible superconductivity of the iced matter of the rings of Saturn (based on the data of Voyager and Pioneer space missions) allow us to explain many phenomena which have not been adequately understood earlier. By introducing into planetary physics the force of magnetic levitation of the superconducting iced particle of the rings, which interact with the magnetosphere of the planet, it becomes possible to explain the origin, evolution, and dynamics of the rings; to show how the consequent precipitation of the rings' matter upon the planet was concluded; how the rings began their rotation; how they were compressed by the magnetic field into the thin disc, and how this disc was fractured into hundreds of thousands of separated rings; why in the ring B do exist "spokes"; why magnetic field lines have distortion near by ring F; why there is a variable azimuth brightness of the ring A; why the rings reflected radio waves so efficiently; why there exists strong electromagnetic radiation of the rings in the 20,4 kHz-40,2 MHz range and Saturnian kilometric radiation; why there is anomalous reflection of circularly polarized microwaves; why there are spectral anomalies of the thermal radiation of the rings; why the matter of the various rings does not mix but preserves its small-scale color differences; why there is an atmosphere of unknown origin nearby the rings of Saturn; why there are waves of density and bending waves within Saturn's rings; why planetary rings in the solar system appear only after the Belt of Asteroids (and may be the Belt of Asteroids itself is a ring for the Sun); why our planet Earth has no rings of its own.

This paper begins with a complete description of the complex Poynting theorem, followed by a rigorous study of the generalized resonance in a multi-antenna system. The condition generating the generalized resonance is discussed, which is the balance of the electromagnetic fields energy stored in the antennas open system. The matrix expression of the generalized resonant factor (GRF) is derived. On this basis, the generalized Foster reactance theorem for an arbitrary antenna system is presented and radiation Q is used to further describe the generalized resonance behaviors. Some practical examples have shown that the generalized resonance may take on the phenomena of strong and sharp fields in the near zone and super-directivity in the far zone of the antenna system.

The binary Genetic Algorithm (GA) optimization method is used to simulate antennas from their near-field distribution by a set of infinitesimal dipoles. The infinitesimal dipoles could be of electric and/or magnetic types that produce the near field of the actual antenna and thus the same far field. The method is verified using near fields from known infinitesimal electric and/or magnetic dipoles. Some simple antennas have been simulated by infinitesimal dipoles such as dipole, loop, waveguide, and dielectric resonator antenna. The obtained equivalent dipoles from single frequency measurements are found to be valid for certain frequency band.

An efficient technique for the solution of large-scale electromagnetic radiation and scattering problems arising from the surface integral equations and the method of moments is developed. The conventional MoM basis and testing functions are used to discretize the integral equations resulting in a dense impedance matrix. A block-partitioned wavelet transform is then employed to sparsify the matrix. Full advantage is taken of the sparse nature of the mathematical model to solve the system of equations by means of the recently introduced Stabilized Bi-Conjugate Gradient method (Bi-CGSTAB (l)). Various problems are considered involving perfect electric conductor and dielectric material. Results are compared to the corresponding results obtained via the direct solution, or LU decomposition, of the original MoM dense matrix. Excellent results are obtained in a very efficient manner. By block partitioning the MoM impedance matrix as it is built and performing the wavelet transform on the matrix blocks, analysis of very large electromagnetic problems becomes possible in a very efficient and accurate manner.

The accuracy of a spherical wave expansion is examined when the expansion is calculated from incomplete data of the radiation pattern, i.e., when field data on a part of the far-field sphere is missing. The effect of antenna size and truncation index on the interpolation capacity of a SWE is examined by using an analytical expression for the radiation pattern of wire antennas of different lengths. The error of the SWE is seen to increase drastically when the smallest diameter of the dead zone surpasses the length of a period of the highest included wave function. The influence of the size and shape of the dead zone is studied by the aid of a measured pattern, of which a part of the field data is ignored. Two different ways are proposed for estimating the accuracy of the obtained SWE in a practical instance, when the field in the dead zone is unknown.