Radiation of a Hertzian dipole in a short-ended conducting circular cylinder with narrow circumferential slots is presented. Modematching and Fourier transform were utilized to derive a system of simultaneous equations for modal coefficients. Computations were performed to confirm the fast convergence of the series solution.

A novel uni-planar electromagnetic Band Gap (EBG) structure incorporated with inter-digital capacitor and meandered line inductor (ML-ID-EBG) is presented, this novel structure significantly enlarges the fringe capacitance to reduce sized cells, as well as increases the equivalent inductance to widen the relative bandwidth. Its design is detailed in this paper, and several experimental results are presented, the improved properties of the proposed ML-ID-EBG are examined, as compared with a conventional UC-EBG and a novel EBG incorporated only with inter-digital capacitor (ID-EBG).

In this paper the electromagnetic wave scattering from multilayered cylindrical structures is studied for a normally incident plane wave with linear (TE or TM), circular and elliptical polarizations. The cylindrical layers may be composed of any combination of dispersive common materials and metamaterials. The addition theorems for the cylindrical waves are used for the EM wave analysis. The objective of this study is to decrease or increase the Radar Cross Section (RCS) in an ultra wide band width. The optimization is based on the Method of Least Squares (MLS), employing a novel combination of the Genetic Algorithm (GA) and Conjugate Gradient (CG), where the global search for the minimization point is performed by GA and the local search is done by CG, which greatly speeds up the search algorithm. The behaviors of various combinations of common materials and metamaterials for reduction of RCS are studied. Furthermore, the procedures for selection of correct signs for metamaterial parameters, namely ε, μ, k and η are presented.

An ultra-wideband (UWB) U type monopole antenna fed by a coplanar waveguide (CPW) is proposed. It has low profile and very compact size (14.48mm×28.74mm×0.8 mm). It provides an wide impedance bandwidth ranging from 3.08 GHz to about 12.75 GHz adjustable by variation of its parameters, such as the relative permittivity and thickness of the substrate, width, and feed and ground plane dimensions. Parametric study is presented. Details of the proposed ultra-wideband design are described. Simulation results are presented and discussed in this paper.

The adiabatic parameter dynamics of non-Kerr law optical solitons is obtained in this paper by the aid of soliton perturbation theory. The various kinds of perturbation terms that arise exhaustively in the context of optical solitons are considered in this paper. The new conserved quantity is also used to obtain the adiabatic dynamics of the soliton phase in all cases of non-Kerr laws studied in this paper. The non-Kerr law nonlinearities that are considered in this paper are power law, parabolic law as well as the dual-power law.

A tunnel diode integrated E-shaped patch antenna is proposed and analyzed using equivalent circuit concept. It is found that bias voltage of tunnel diode controls the performance of the antenna. Various tunable frequency bands are obtained by selecting suitable bias voltage while antenna topology remains unchanged. Bandwidth of the tunnel diode integrated patch improves to 40.26% over the 32.58% bandwidth of the patch. The radiation pattern also varies with bias voltage and a considerable improvement in beamwidth is observed however radiated power remains almost same.

This paper presents a square cylindrical monopole antenna easily fabricated using a cross-shaped metal plate for wideband omnidirectional operation. A prototype of the proposed antenna with a cross-sectional area of 8 × 8mm² is implemented, and the antenna provides a wide operating bandwidth of about 7.5 GHz (1.8-9.4 GHz here), making it very promising for WMAN operation with the 802.16e standard in the 2 to 6 GHz. In addition, over the operating bandwidth, the antenna shows very good omnidirectional radiation patterns.

The estimation of the directions-of-arrival (DoAs) of multiple signals is a topic of great relevance in smart antenna synthesis and signal processing applications. In this paper, a memory-based method is proposed to compute the maximum likelihood (ML) DoA estimates. Such a conceptually-simple technique is based on the datasupported optimization (DSO) and the estimation of signal parameters via rotational invariance technique (ESPRIT), but fully exploits a memory mechanism for improving the estimation accuracy especially when dealing with critical scenarios characterized by low signal-tonoise ratios (SNR) or/and small number of snapshots. Simulation results assess the potentialities and limitations of the proposed approach that favorably compares with state-of-the-art methods.

In this paper, a new evolutionary learning algorithm based on a hybrid of improved real-code genetic algorithm (IGA) and particle swarm optimization (PSO) called HIGAPSO is proposed. In order to overcome the drawbacks of standard genetic algorithm and particle swarm optimization, some improved mechanisms based on non-linear ranking selection, competition and selection among several crossover offspring and adaptive change of mutation scaling are adopted in the genetic algorithm, and dynamical parameters are adopted in PSO. The new population is produced through three approaches to improve the global optimization performance, which are elitist strategy, PSO strategy and improved genetic algorithm (IGA) strategy. The effectiveness of the proposed algorithm has been compared with GAs and PSO, synthesizing a circular array, a linear array and a base station array. Results show that the proposed algorithm is able to adapt itself to different electromagnetic optimization problems more effectively.

The problem of wide bandwidth management in ultra-high resolution SAR systems can be solved by adopting stepped chirps and applying synthetic bandwidth approach. However, high resolution SAR image formation is a non-separable 2-D impulse compression processing, so the synthetic bandwidth procedure should be modified correspondingly with the image formation algorithm adopted. This paper demonstrates the application of synthetic bandwidth approach in SAR Polar Format Algorithm (PFA) using the deramp technique. The problem of motion compensation between the sub-pulses within a burst is discussed, and the signalpro cessing flows are investigated in detail. The presented approach is validated by point target simulation.

In the military applications, electro-optics and electromagnetics features of the cloths made of special textile structures and certain fibers play an important role in producing textile characterized with high ability of camouflage. This means not allowing enemy to precisely determine the moving and mute targets using available radar or any other electro-optics sensors. The aim of this paper is to determine the effect of the composite fabrics structure parameters on the fabrication of a resistive sheet used in many radar applications. The objective sheet can be used as a lossy sheet in absorbing mechanism. The radar absorbing mechanism has been studied with emphasis on the single layer structure mechanism with a resistive sheet. Fabric structure of the resistive sheet was accurately chosen and coated with lossy material. For coating, several formulas of fabrics using carbon black were tested to determine the best chemical treatment in accordance with their functional performance. Lab measurements have been done to get optimum formulas and optimum fabrics structures for high radar absorption performance.

In this communication, we theoretically report the reflection properties of a photonic crystal with alternate layers of air and GaAs for specified values of the lattice parameters. By employing the transfer matrix approach, the reflection spectra of the layered media are obtained for chosen sets of number of unit cells and incident angles. It is observed that the photonic crystals with different number of unit cells completely reflect a wide band in the infrared region of radiation. Also, we find that the reflectivity decreases and the completely reflected bands are shifted towards lower wavelength side with increase in the incident angle. Further, the reflected broadbands in the reflection spectra correspond to the forbidden ranges of wavelength obtained by using the analogy of Kronig-Penney model. It indicates that the completely reflected ranges are forbidden bandgaps, which is considered as an important feature of the proposed photonic crystals.

In this paper an effective numerical method for determining the scattered electromagnetic fields from thin wires is presented and discussed. This problem is modeled by the integral equations of the first kind. The basic mathematical concept is the method of moments. The problem of determining these scattered fields is treated in detail, and illustrative computations are given for several cases.

The asymptotic strip boundary condition (ASBC) is applied to analyze the solution of the electromagnetic scattering from a conducting cylinder coated with a homogeneous linear material layer and loaded with conducting helical strips. Such homogeneous material layer can be implemented by a conventional dielectric material, a single negative (SNG) or double negative (DNG) meta-material layer. A study of different materials' constitutive parameters is presented with accordance to Drude and Lorentz material modeling. The boundary condition assumes that the strips are rounded around the coated cylinder in a helical form and both the strip's period and the spacing between the helix turns are very small and mathematically approaching the zero. Scattering due to normal and oblique incident plane waves (θ_i, φ_i) of arbitrary polarization using the series solution is also computed. A number of parametric studies were investigated to illustrate the advantages of using metamaterials compared with conventional coating materials in terms of strip's rounding pitch angle and coating layer electrical thickness variations. It is also shown that for SNG materials, modified Bessel functions are used to accept negative arguments. Coating with metamaterials proves to achieve higher forward scattering compared with conventional materials for the same electrical coating thickness.

This paper proposes a novel beamforming technique to form an arbitrary-shaped cell for the high altitude platforms (HAPs) mobile communications. The new technique is based on pattern summation of individual low-sidelobe narrow-beams which constitute the desired cell pattern weighted by an amplitude correcting function. The new cell pattern can be adapted to cover the main highways forming worm-shaped cells which may cover the highway for long distances up 100km and it will has an important role in reducing frequent handoffs and signaling traffic of location updating from moving users over the long highways.

The electronic structure of finite parabolic GaAs/Al_xGa_1-xAs superlattices is studied. A detailed analysis of the miniband formation is given and the importance of all system parameters is discussed. The dependence of the equidistant miniband separation on the superlattice size is revealed. A comparison with different theoretical methods and experimental data is presented. The calculations are conducted in the framework of the semi-empirical sp³s^* tight-binding model including spin applying the Green function formalism and the Surface Green Function Matching Method (SGFM) method.

This paper presents a proposal of taking the left-handed material as the structural defects of one-dimensional photonic crystals and uses the transfer matrix method to analyze the band-gap of that structure. The simulation result shows that the structure investigated can be considered as a narrow pass band optical filter. By tuning the refractive index of the left-handed material, the ideal transmission rate in the pass band is as higher as 99.99%, while in the band-gap is lower than 0.01%. In addition, we show that the bandwidth can be increased by reducing the cycle number of the photonic crystals.

The paper describes a theoretical investigation into a limited bandwidth operation of a microstrip reflectarray. Two main factors limiting the bandwidth are considered. One is related to the requirement of phase compensation to convert a spherical wavefront launched by a feed into a planar wavefront. The other one is linked to the limited phasing range of microstrip antenna elements. The two factors contribute to the reflectarray phasing errors that in turn reduce its gain as a function of frequency. Simple formulas for an upper bound of gain bandwidth are derived, assuming the phase compensation by the elements is independent of frequency changes and verified against the results produced by other researchers. It is shown that the phase errors incurred in the path equalization to obtain conversion from spherical to planar wavefronts have a more profound effect on the reduction of operational bandwidth of the reflectarray than the phase truncation implemented on the required phase from each element.

In this paper the problem of electromagnetic scattering from the resistive surfaces is carefully surveyed. We model this problem by the integral equations of the second kind. A new set of orthogonal basis functions is used to solve these integral equations via collocation method. Numerical solutions of these equations are given for some cases of resistance distributions. Presented method in this paper can be easily generalized to apply to other cases.

This paper presents a comprehensive study on the hybrid mode analysis of a periodic structure in a Suspended Microstrip and Broadside-coupled Suspended Stripline. The analysis has been use of Floquet's theorem in special harmonics to express the field equations in various sub regions of the periodic loaded suspended substrate. Their characteristic equation is derived, using the Galerkin's procedure. The unknown electric field distribution in the substrate region, corresponding to one unit cell of the periodic structure is specified in terms of suitable basis functions. The characteristic of slow wave properties, resonance behavior and the passband-stopband characteristics are at the millimeter wave frequencies as a various structural parameters are presented.