Mohammed Hussein Bataineh

Synthesis of Aperiodic Linear Phased Antenna Arrays Using Particle Swarm Optimization

In this article, the particle swarm optimization (PSO) algorithm is used to synthesize an optimal linear array. The technique is applied to synthesize a linear antenna array in the Chebyshev sense or to eliminate a grating lobe. This is may be achieved by optimizing the excitation currents and/or the relative locations of the array elements. These various design parameters are considered in this paper. In synthesizing equiripple radiation patterns, two approaches were used. The excitation currents feeding the array or the spacing between the array elements are optimized. It is to be noted that the desired equal side lobes level is achieved simultaneously with the narrowest possible beamwidth. Although the optimization problem may become nonlinear, convex, or nonconvex, especially if the interelement distances are the optimized parameters, it can be handled using the PSO algorithm. The PSO is simple to implement and does not require evaluation of gradients or coded parameters. In order to effectively utilize this algorithm, it is important to define an objective function that returns a single number to enable the PSO algorithm to minimize it. In this paper, the objective function is formulated to take into consideration both the lobe level and the main beam width. The results obtained using the particle swarm optimization technique are in excellent agreement with those available in the literature.

Application of multiple scales analysis and the fundamental matrix method to rugate filters: initial-value and two-point boundary problem formulations

In this paper, the filtering problem of apodized rugates is solved by deriving first-order, as well as second-order, coupled-mode equations via the perturbation method of multiple scales. The first-order perturbation equations are the same as those of coupled-mode theory. However, the second-order perturbation expansion is more accurate, and permits the use of larger amplitudes of the periodic index variation of the rugate. The coupled-mode equations are solved numerically by using two different formulations. The first approach is a two-point boundary-value problem formulation, based on the fundamental matrix solution, that is essentially the exact solution for the unapodized rugate. The second approach is an initial-value problem formulation, that uses backward integration of the coupled-mode equations. Comparison with the characteristic matrix method is made for the case of unapodized rugate in terms of speed and accuracy, and it is found that the fundamental matrix solution is the fastest. The accuracy of the multiple scales solution is measured in terms of the amplitude error and the phase error of the filters spectral response, taking the characteristic matrix solution as a reference for the unapodized rugate. The proposed formulations are utilized to calculate the spectral response of apodized rugates.

Microwave filter response of nonuniformly corrugated circular waveguide

A corrugated circular waveguide is proposed as a microwave filter. The analysis is carried out using the perturbation method of multiple scales for the case of TM modes. The analysis concerns the interaction of two and four modes satisfying the resonant condition (Bragg condition) imposed by the periodicity of the waveguide wall. The coupled mode equations derived via the method of multiple scales are used to formulate the filtering problem as a two-point boundary-value problem which is solved numerically. Desirable filtering characteristics may be realised by introducing tapered as well as chirped corrugations to control the frequency response of such a wave filter. In case of two-mode interaction the side ripples can be eliminated by tapering the waveguide wall. In the four-mode interaction case, a multichannel filter may be realised by combining taper and chirp.

Using defected ground structure (DGS) to improve nonuniform microstrip bandpass filters' performance

In this paper, nonuniform bandpass filter with defected ground structure is presented. The width of the designed filter, with U shape and nonuniform, shape is obtained using an optimization process. Additionally, multiband is obtained by using defected ground structure (DGS). The performance of the proposed design is presented using high frequency structure simulator (HFSS) and computer simulation technology (CST) software packages.

Pulse compression using Fiber Bragg gratings

Fiber Bragg gratings (FBGs) are one of the most important enabling technologies for fiber optics communications in the last decade. Their market growth was in 1995 and their use in telecommunications and sensors has grown largely. FBGs can be designed to have an almost arbitrary, complex spectral response, thus it has various applications in telecommunications. One of these important applications of FBGs is pulse compression or dispersion compensation. FBGs have been chosen to compensate dispersion among different techniques since it has low insertion losses. So, in this paper, two cases for dispersion compensation system using fiber Bragg gratings (FBGs) are proposed. First, a transmission-based system for dispersion compensation with no need for chirping or circulator so saving the insertion losses. Second, a reflective-based system, where chirping along with circulator should be employed. The results are validated by using Optical Grating (OptiGrating) software package.

Band structure of a parallel-plate waveguide filter having phase-shifted square-wave corrugations

In this paper, we study the effect of harmonics of phase-shifted square-wave corrugations on the different stopbands of a corrugated parallel-plate waveguide supporting TM waves. The stopbands are characterized by simultaneous occurrence of first-order and higher-order Bragg interactions. Coupled mode equations of two or four modes are derived via the method of multiple scales. Above cutoff of a higher-order mode, it is found that three resonance conditions must be satisfied: a first-order Bragg condition for the higher-order mode and a higher-order Bragg condition for the dominant TM10 mode, and a third condition coupling the two modes. A design of a multiple stopband filter for interference suppression in UWB applications is given showing all stopbands above cutoff of the TM10 and higher-order modes up to TM50 by including effects of higher harmonics of the structure. The bandwidth of each stopband is controllable by varying the phase shift between corrugations on the two walls of the waveguide. The fundamental matrix method is used to solve the filtering problem numerically.

Gaussian Recompression in Cascaded Transmission Gratings

A step-chirped step-apodized transmission grating is proposed to maximize compression ratio, minimize compensating length, and improve recompressed pulse shape of a 40-ps (FWHM) Gaussian pulse, broadened and chirped upon transmission in a 100 km length of optical fiber. This is accomplished by tuning a single transmission side lobe to lie within or coincide with the pulse bandwidth at the upper edge of the photonic band gap of each grating section. Analysis is via the theory of uniform cascaded gratings achieving a compression ratio of 5.625 in a four-section grating 3.422 cm long.

Plane wave visualisation on a dielectric-dielectric interface

In this paper, the behaviour of an arbitrarily polarised plane wave on a dielectric-dielectric interface is investigated. By imposing the appropriate boundary conditions the Fresnel transmission and reflection coefficients are derived. Using these coefficients various three dimensional as well as contour plots are produced using a MATLAB code in order to illustrate the refraction and the reflection usually encountered at an interface. Snells law and the Brewster angle are discussed within the context of the analysis.

An Alternative Approach for Equating the Side Lobes of Linear Arrays

An alternative approach, based on an iterative least-squares optimization technique, for the design of antenna arrays exhibiting equal side lobes in their radiation patterns is presented. For a given number of elements equispaced by a constant amount, the algorithm returns the excitation currents under the condition that all side lobes are at the same level. The results show excellent agreement with those reported using other approaches.

A fast algorithm for calculating the reflectance of nonabsorbing multilayer dielectric films

In this paper, filtering nondesired bands of a polychromatic beam using multilayer dielectric films is described. The stop-bands could be placed anywhere in the spectrum range by carefully choosing the thickness and the refractive index of each layer. The total thickness of the structure, or the number of layers, affects the frequency response of the filter in such a way that increasing the number of coefficients of a digital filter or increasing the number of elements in an antenna array affects the respective responses. From computational point of view, reduction of computational time has been achieved by computing the characteristic matrix just once for similar layers. Illustrative examples are also given.