In this paper a method is introduced and applied to calculate the effects of an external field on a circular symmetric microstrip transmission line. The primary/secondary field idea is used for this purpose. The primary field is determined analytically for the cases of normal TM^z and TE^z incidence. The secondary field is determined using multi-conductor transmission line theory. The method is applied to a special structure and some useful results are obtained.

This paper shows the ability to use a continuous wave (CW) radar as an instrument to search for trapped alive persons in demolished buildings and ruins. The utilized operation principle is the detection of the Doppler frequency shift of the E/M wave when it is reflected by a slightly moving part of a living human body. The presented system has gone through several prototype development phases. Many parameters and alternative implementations have been tested in both real and simulated sites. A system analysis is carried out and presented followed by a presentation of the signal processing techniques. The inherent difficulties for the realization and practical exploitation of such a system are discussed. Results from tests of the system are also presented.

Abstract-Ever since the concepts of "focus waves modes" and "electromagnetic missile" were introduced in the open literature almost two decades ago, extensive research work has been carried out to arrive at physically realizable applications for such concepts. In this paper, an ultra-wideband (UWB) electromagnetic missile with the time variation of a generalized Gaussian pulse (GGP) is generated based on the principle of focused-array beamforming. The radiation pattern, or array factor, of the focused-planar array is derived, and focused-energy patterns are computed to demonstrate the decaying behavior of the radiation energy of the electromagnetic missile as a function of distance travelled from the array to an observation point. The focused-energy patterns show that the depth-of-focus, or focusing bandwidth, is directly proportional to the focusing distance, and inversely proportional to the signal frequency bandwidth and array dimension. The focusing bandwidth is a measure of how well the energy is concentrated in the vicinity of the focusing point, and it is a useful parameter for radar ranging as well as imaging. In practice, the trade-off between the focusing distance, frequency bandwidth, and array dimension for improved focusing capability (or resolution) is of interest, in particular in the case of the ground-probing radar (GPR).

In this paper, we investigate various methods for solving a time-domain electric field integral equation (TD-EFIE) and a timedomain magnetic field integral equation (TD-MFIE) for analyzing the transient electromagnetic response from three-dimensional (3-D) dielectric bodies. The solution method in this paper is based on the method of moments (MoM) 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 using a set of orthogonal basis functions that is derived from the Laguerre functions. These basis functions are also used as the temporal testing. Numerical results involving equivalent currents and far fields computed by the proposed TD-EFIE and TD-MFIE formulations are presented and compared.

Optimization and parameter estimation techniques have been employed for many years as a method of improving and exploring designs in numerous areas. As the designs of antennas and antenna arrays become more complex in nature, optimization techniques such as Bayesian estimation or genetic algorithms have become more necessary in the design process. These techniques provide methods for not only the design process, but also for operation simulations such as element failure corrections as well. This paper will deal with Bayesian optimization techniques for antenna and antenna array design as an alternative to other techniques. Through the use of Bayesian inference techniques, probability and information theory can be applied to a design problem to improve the operation within a range of specifications. Examples provided show that how this method allows for the examination of an entire parameter space of a linear array so that the best fitting solutions can be quickly and efficiently examined and improvements can be implemented.

The characteristics of a bow-tie slot antenna with tapered tuning stubs fed by a coplanar waveguide (CPW) are investigated. The effects of the antenna dimensional parameters are studied through simulation results and design procedure is developed and verified for different frequency bands. The antenna shows wideband characteristics for radar and wireless communication applications. Numerical simulations and measurements indicate that 73% bandwidth can be obtained using the developed design procedure.

The well-conditioned asymptotic waveform evaluation (WCAWE) is applied to the MoM solution of scattering from microstrip antennas so that the reduced order model is obtained to efficiently evaluate the frequency response over a broadband in this paper. In the traditional asymptotic waveform evaluation (AWE) method, the ill conditioning usually leads to stagnation in the momentmatching process.The WCAWE eliminates this difficult.A t the same time, to cover the entire bandwidth, a multipoint automatic WCAWE method is also proposed.Numerical examples are given to illustrate the accuracy and robustness of this method.

Building an anechoic chamber involves a substantial investment both financially and in physical space. Hence, there is much interest in trying to reduce the required investment while still maintaining adequate performance. The performance of an anechoic chamber depends on the type, size, and array configuration of the absorber elements as well as the geometry of the screened room on which the inner surfaces are covered with RF absorbers. If the room geometry is designed such that an electromagnetic ray from the transmitter will only reach the receiver antenna after a few reflections, the wave energy may be sufficiently damped after a few bounces off the absorbing walls and ceiling. Hence, lower cost RF absorbers can be used to make the anechoic chamber design more economical. In this paper, a variant of beam-tracing technique is used for modeling of anechoic chamber to study the normalized site attenuation (NSA) performance of the anechoic chamber. This allows the chamber performance to be predicted prior to the actual construction. The ma jor advantage of beam-tracing over ray tracing is the path loss information at multiple receiver locations can be determined simultaneously as opposed to running a ray tracing simulation for each receiver location one at a time. As a result, the computing time is greatly reduced. This feature is particularly useful in calculating the field strength at different heights of the receiving antenna in EMC site calibration procedure. The efficient modeling tool has given rise to the successful design and construction of an asymmetrical shape anechoic chamber that supports various measurement needs including EMC tests at the Multimedia University, Malaysia.

An optimization problem for designing non-uniformly spaced, linear arrays is formulated and solved by means of an improved genetic algorithm (IGA) procedure. The proposed iterative method is aimed at minimizing the side-lobes level and thinning the array by optimizing the element positions and weights. Selected examples are included, which demonstrate the effectiveness and the design flexibility of the proposed method in the framework of electromagnetic synthesis of linear arrays.

The study of periodically dielectric-slab-loaded TE10 waveguide structures of conductive walls and finite length is carried out by using wave analysis techniques.The principal aim is to design and construct a highly dispersive waveguide keeping losses to a minimum. Passing a properly frequency modulated wave through this waveguide, pulse compression phenomena take place. Frequency modulated waves, incident to a finite length periodic loaded waveguide, are studied.The aim is to achieve optimum pulse compression, by taking into account all wave phenomena involved. In order to minimize the reflected (at the input) and maximize the transmitted (at the output) waves of the compressor structure, a staggered-tapered structure of dielectric slabs inside the waveguide is utilized to match the incident waves. The slab longitudinal discontinuity nature prevents the appearance of field singularity points that could hinder the operation of the compression mechanism. An exact Fourier analysis is carried out to compute the compressed wave field intensities.Optimization techniques are used to achieve the best compression and matching conditions for various realistic dielectric materials, having permittivities εr in the range of 9 to 36 and loss factors tan(δ) in the range of 0.01 to 0.00001. Experimental results, obtained by carrying out measurements on prototype waveguide structures, built in our laboratory, present pulse compression phenomena, but do not show good agreement with theory.

The differential method for arbitrary profiled onedimensional gratings made of anisotropic media is reformulated by taking into account Li's Fourier factorization rules [10] though the present formulation uses the intuitive Laurent rule only. The study concerns arbitrary profiled gratings with both types of electric and magnetic anisotropy, and includes the case of lossy materials. Diffraction efficiencies computed by the present formulation are compared with previous ones, and numerical results show that convergence of the present formulation is superior to the conventional one and comparable convergence with the previous works based on Li's rules.

We are interested in first order v/c velocity effects in scattering problems involving motion of media and scatterers. Previously constant velocities have been considered for scattering by cylindrical and spherical configurations. Presently time-varying motion - specifically harmonic oscillation - is investigated. A firstorder quasi-Lorentz transformation is introduced heuristically, in order to establish relations to existing exact Special-Relativistic results. We then consider simple problems of plane interfaces, normal incidence, and uniform motion, in order to introduce the model: Starting with an interface moving with respect to the medium in which the excitation wave is introduced, then considering the problem of an interface at rest and a moving medium contained in a half space. The latter corresponds to a Fizeau experiment configuration. Afterwards these configurations are considered for harmonic motion. This provides the method for dealing with the corresponding problems of scattering by a circular cylinder, involving harmonic motion. The present formalism provides a systematic approach for solving scattering problems in the presence of time-varying media and boundaries.

This paper presents a novel design of a triangle slot antenna fed by a coplanar waveguide. The antenna consists of a symmetric triangle slot tuned by a metal stub and slot hat. The antenna exhibits a wide bandwidth of 57% for X-band frequencies with an average gain of 4.5 dB and cross polarization level of −10 dB. In addition to being small in size, the coupling between the two elements of this type antenna is in the order of −15 dB or less, which makes it a good candidate for a phased array system. A linear array of 8- elements is simulated and results indicated that a steering angle of 50^◦ is attainable without grating lobes.

Four-dimensional conformal transformations due originally to Bateman have been used in the past by Hillion as alternative approaches to focus wave mode solutions to the 3D scalar wave equation. More recently, more extended families of focus wave mode solutions to the 3D scalar wave equation have been derived by Borisov and Utkin, as well as Kiselev, based on Bateman transformations together with a dimension-reduction approach, whereby the wave function is separated incompletely into a product of two functions. One particular goal in this exposition is to comment on and extend the work of Borisov and Utkin and simplify and extend the method used by Kiselev. More generally, however, the aim is to show that an already existing method, known as the bidirectional spectral representation, when examined in conjunction with Bateman conformal transformations, encompasses the Borisov-Utkin-Kiselev theories as special cases and allows a systematic derivation of extended families of FWM-type localized waves beyond the ranges of their applicability.

In the framework of buried object detection and subsurface sensing, some of the main difficulties in the reconstruction process are certainly due to the aspect-limited nature of available measurement data and to the requirement of an on-line reconstruction. To limit these problems, a multi-source (MS) learning-by-example (LBE) technique is proposed in this paper. In order to fully exploit the more attractive features of the MS strategy, the proposed approach is based on a support vector machine (SVM). The effectiveness of the MS-LBE technique is evaluated by comparing the achieved results with those obtained by means of a previously developed single-source (SS) SVMbased procedure for an ideal as well as a noisy environment.

Space-Time reversal symmetry properties of free-Space electromagnetic Green's tensors for complex and bianisotropic homogeneous media are discussed. These properties are defined by symmetry of the medium under consideration, of the point sources and of the vector S connecting the source and the point of observation. The constraints imposed on Green's tensors by the restricted Time reversal, by the center and anticenter of symmetry are independent on the vector S orientation. Other Space-Time reversal operators lead to constraints on Green's tensors only for some special directions in Space. These directions are along the (anti)axes and (anti)planes and normal to the (anti)axes and (anti)planes. The full system of the continuous magnetic point groups for description of Space-Time reversal symmetry of Green's tensors is defined and a general group-theoretical method for calculation of simplified forms of Green's tensors is presented.

In this paper, a neural network is used to implement an optimized objective function for a genetic algorithm (GA) for application on array antenna design optimization. Traditional GAs are inefficient because a large amount of data that describes the problem space is discarded after each generation. Using the neural network enhanced genetic algorithm (NNEGA), this redundant information is fed back into the GA's objective function via the neural network. The neural network learns the optimal weights of the objective function by identifying trends and optimizing weights depending on the knowledge that it accumulates in-situ. The NNEGA is successfully applied to challenging array antenna design problems. This use of neural network to optimize a multi-objective function for the GA is a new idea that is different from other hybridization of GA and NN.

This paper studies the propagation of solitons through an optical fiber, with strong dispersion-management in presence of perturbation terms. The adiabatic parameter dynamics of the solitons in presence of such perturbation terms have been obtained by using the variational principle. In particular, the Gaussian and super-Gaussian pulses have been considered.

The electromagnetic-wave propagation through a medium consisting of two dielectric half-spaces with a plate in between, has been investigated. The half-spaces are isotropic with their dielectric permittivity depending only on the z coordinate. The plate is anisotropic, and the components of its dielectric permittivity tensor are also z-dependent. For the first time, the sufficient conditions allowing the transformation of the system of Maxwell's equations into two independent equations, are ascertained. For an arbitrary z-dependence of the dielectric permittivity, the plate's reflectance and transmittance coefficients are obtained, this result being a generalization of the Fresnel formulas. We have considered both determinate and random dependences of the dielectric permittivity on the z-coordinate, and the plate's full-transparency conditions are specified. For a statistically inhomogeneous plate, the conditions of its full opacity are formulated. The Faraday effect in such a medium is studied. The influence of the medium's inhomogeneity on the temporal rotation of the polarization plane of a propagating wave has been demonstrated.

We offer symmetry relations of the translation coefficients of the spherical scalar and vector multi-pole fields. These relations reduce the computational cost of evaluating and storing the translation coefficients and can be used to check the accuracy of their computed values. The symmetry relations investigated herein include not only those considered earlier for real wavenumbers by Peterson and Ström [9], but also the respective symmetries that arise when the translation vector is reflected about the xy-, yz-, and zx-planes. In addition, the symmetry relations presented in this paper are valid for complex wavenumbers and are given in a form suitable for exploitation in numerical applications.