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2007-06-18 PIER Vol. 74, 407-419, 2007. doi:10.2528/PIER07060905

Bandwidth Widening Techniques for Directive Antennas Based on Partially Reflecting Surfaces

Halim Boutayeb, Tayeb Denidni, and Mourad Nedil

The directivity bandwidth of Fabry-Perot directive antennas is first evaluated theoretically. Then, different techniques are proposed to widen the directivity bandwidth of antennas using Partially Reflecting Surfaces. The bandwidths obtained with the proposed solutions are compared to the bandwidth of a classical Fabry- Perot directive antenna.

2007-06-06 PIER Vol. 74, 379-405, 2007. doi:10.2528/PIER07051102

Nonlinear Scattering Effects in Optical Fibers

Sunil Singh, Ramgopal Gangwar, and Nar Singh

The nonlinear scattering effects in optical fiber occur due to inelastic-scattering of a photon to a lower energy photon. This paper describes stimulated Brillouin scattering and stimulated Raman scattering processes. Their thresholds, reduction in power penalty and applications along with comparative study of these effects are also presented.

2007-05-31 PIER Vol. 74, 353-377, 2007. doi:10.2528/PIER07052202

An Efficient Analysis of Vertical Dipole Antennas Above a Lossy Half-Space

Xiao-Bang Xu and Yongfeng Huang

The electromagnetic modeling of radiation by vertical dipole antennas above a lossy half-space is an important subject. The modeling often encounters Sommerfeld-type integrals that are normally highly oscillatory with poor convergence. Recently, an efficient computation of the electric field radiated by an infinitesimal electric dipole above a lossy half-space has been reported, in which the Sommerfeld-type integrals are reduced to rapidly-converging integrals. Using such efficiently-calculated electric field as the Green's function, in this paper, an electric field integral equation (EFIE) is formulated for the analysis of a vertical dipole antenna above a lossy half-space. Then, the EFIE is solved numerically employing the Method of Moments (MoM). Sample numerical results are presented and discussed for the current distribution as well as the input impedance and radiation pattern of the antenna. In particular, the EFIE solutions of the current distribution on an antenna in free space are checked with that obtained using a traditional approach of solving the Pocklington's equation. Also, the current distributions on an antenna above a very lossy halfspace are checked by comparing them with that for the antenna above a PEC plane. Data of the current distribution and the input impedance show that for an antenna close to the media interface separating the two half-spaces, the electromagnetic parameters of the lower half-space can significantly affect the antenna characteristics. The radiation patterns of the antenna presented all exhibit properties as expected and similar to that documented in literature for infinitesimal vertical dipoles above a lossy half-space.

2007-05-31 PIER Vol. 74, 341-351, 2007. doi:10.2528/PIER07051802

Analysis of Balanced Composite Right/Left Handed Structure Based on Different Dimensions of Complementary Split Ring Resonators

Jia-Xiao Niu and Xi-Lang Zhou

In this paper, rectangular shape complementary split ring resonators (CSRRs) with different dimensions are introduced to realize balanced composite right/left handed (CRLH) structure. As the dimensions of CSRRs is altered, the required series capacitance should also be modified and the propagation characteristics will be changed, which gives the facility of designing microwave/RF components using the balanced CRLH structure. The propagation characteristics of proposed structures are demonstrated by simulated and measured results, which are in good agreement.

2007-05-30 PIER Vol. 74, 319-340, 2007. doi:10.2528/PIER07051702

Design Equations of Two-Dimensional Dielectric Photonic Band Gap Structures

M. El-Dahshory, Ahmed Attiya, and Essam Hashish

This paper presents simple formulas for designing different configurations of two-dimensional photonic band gap (PBG) structures. These formulas are obtained by interpolating full wave analysis based on the plane wave expansion method. The design parameters of these formulas include the physical dimensions of the unit cell and the electrical properties of both host and inclusion in the structure. These formulas represent an efficient and fast method to obtain the band gap and the center frequency of different PBG structures.

2007-05-24 PIER Vol. 74, 309-317, 2007. doi:10.2528/PIER07051406

Multiple Targets Detection Method Based on Binary Hough Transform and Adaptive Time-Frequency Filtering

Wei Xue and Xiao-Wei Sun

When the echo energy of multiple targets of vehicle volume detecting radar diverge greatly, small targets are easily masked by the platform of large targets, it is difficult to detect the all the targets by the Wigner-Hough Transform simultaneously. In this paper, a method based on binary Hough Transform and adaptive time-frequency filtering is proposed, which can avoid the problems of detecting the platform of large targets as well as platform masking of small targets and detect all the targets with different energy at the same time. The experimental results show the method has good performance and high practical value.

2007-05-24 PIER Vol. 74, 291-307, 2007. doi:10.2528/PIER07042603

Reconstruction of 2D PEC Targets Using Limited Scattered Information

Jing Wu and Tie-Jun Cui

An efficient method is proposed in this paper to reconstruct the shape of a two-dimensional perfectly electrically conducting (PEC) target using limited scattered information. Based on the physical optics approximation, a Fourier transform relation has been obtained between the PEC target and the scattered fields. In theory, all scattered-field data are required for the reconstruction in the whole angle range (from 0 to 2π) and in the whole frequency range (from 0 to ∞). However, such data are impossible in practical applications. In this paper, we have discussed the influence of limited frequencies and limited incident angles on the imaging, where a Pade interpolation technique has been developed to obtain the scattered information in the whole angle range from limited-angle information. In order to overcome the ill-posed problem in the interpolation, the Tikhonov regularization has been used. Reconstruction examples are given to validate the efficiency of the proposed approach.

2007-05-22 PIER Vol. 74, 273-289, 2007. doi:10.2528/PIER07050904

Transient Solutions of Maxwell's Equations Based on Sumudu Transform

Malek G. Hussain and Fethi Bin Muhammad Belgacern

The Sumudu transform is derived from the classical Fourier integral. Based on the mathematical simplicity of the Sumudu transform and its fundamental properties, Maxwell's equations are solved for transient electromagnetic waves propagating in lossy conducting media. The Sumudu transform of Maxwell's differential equations yields a solution directly in the time domain, which neutralizes the need to perform inverse Sumudu transform. Two sets of computer plots are generated for the solution of Maxwell's equations for transient electric field strength in lossy medium. A set of plots presents the Sumudu transform of the transient solution and another one presents inverse Sumudu transform. Both sets of plots reveal similar characteristics and convey equal information. Such property is referred to as the Sumudu reciprocity.

2007-05-22 PIER Vol. 74, 241-271, 2007. doi:10.2528/PIER07050902

Two-Dimensional Electromagnetic Scattering of Non-Plane Incident Waves by Periodic Structures

Koki Watanabe and Kiyotoshi Yasumoto

This paper proposes the pseudo-periodic Fourier transform to analyze the electromagnetic scattering from periodic structures with non-plane wave incidence. The pseudo-periodic Fourier transform converts arbitrary field components into pseudo-periodic functions and the conventional grating theories based on the Floquet theorem become applicable. The inverse transform is given by integrating with respect to the transform parameter over a finite interval and the near field analysis requires numerical integration. Some application examples are numerically examined and the results show good convergence.

2007-05-18 PIER Vol. 74, 217-240, 2007. doi:10.2528/PIER07042401

Analysis of Planar Dielectric Multilayers as FSS by Transmission Line Transfer Matrix Method (Tltmm)

Homayoon Oraizi and Majid Afsahi

The transmission line transfer matrix method (TLTMM) is presented for the analysis of multilayer electric structures as frequency selective surfaces (FSS), whereby the reflection, transmission and absorption coefficients, field distribution and power flow may be computed inside and outside of the layers. The TLTMM formulation may be developed for any arbitrary angle of incidence, any polarization (linear TE or TM, circular, elliptical) of the incident plane wave, at any frequency of operation (microwave, millimeter wave, optical), any number dielectric layers with arbitrary thicknesses, lossless or low loss dielectric media, inclusion of dispersion relation, etc. A general formulation is given for both the TE and TM polarization of the incident wave. Several practical situations are treated by TLTMM namely, anti-reflection coatings, high reflection surfaces, computation of the axial ratio of the reflected and transmitted plane waves, distributed brag reflector (DBR), a narrow band filter consisting of two Fabry-Perot resonators, cantor superlattices in optics, field distribution and power flow for a multilayer structure. Consequently, it is verified that TLTMM is capable of analysis a variety of practical multilayer dielectric structures.

2007-05-15 PIER Vol. 74, 195-216, 2007. doi:10.2528/PIER07042201

Analysis of Two-Dimensional Magneto-Dielectric Grating Slab

Ahmed Attiya, Ahmed Kishk, and Allen Wilburn Glisson

Vectorial modal analysis of a 2-D magneto-dielectric grating structure is presented. The modal analysis is combined with the generalized scattering matrix to obtain the transmission and reflection coefficients of multilayered 2-D magneto-dielectric grating slabs. The results are verified with available commercial codes. Physical interpretation of the grating slab behavior is introduced. An equivalent homogeneous magneto-dielectric slab is found using a simple approach for extracting the equivalent permittivityand permeability. Several examples are presented to find the relation between the physical parameters of magneto-dielectric grating slabs and their equivalent parameters. Emphasis on the possibilityof designing a metamaterial with equivalent negative permittivityand/or negative permeability by using these grating structures is considered.

2007-05-13 PIER Vol. 74, 181-194, 2007. doi:10.2528/PIER07050202

Omnidirectional Reflection Bands in One-Dimensional Photonic Crystal Structure Using Fullerene Films

Sanjeev Srivastava and Sant Ojha

We study the omnidirectional reflection (ODR) in onedimensional photonic crystal (PC) structures consisting of alternate layers of fullerene-gallium arsenide (GaAs), fullerene-germanium (Ge) and fullerene-telurium (Te). The proposed structures give 100% reflection within a very wide range of wavelength in the visible and in a very narrow portion of near IR region of the EM spectrum. Fullerene (C60) in the form thin film structure is a suitable candidate for the designing the PC structure because alkali-metal doped thin film of fullerene acts as conductor and have almost zero absorption in the wavelength range > 530nm and near IR region. Also, in this region its dielectric constant has very small dependence on the frequency and can be ignored. Thus being a metallic counter part as well as almost frequency independent dielectric constant and easier fabrication technique it is useful in designing the PC structure. The investigation has also been made for the study the role of ambient medium and effect of number of layers in the formation of ODR.

2007-05-11 PIER Vol. 74, 167-180, 2007. doi:10.2528/PIER07041201

Pad Modeling by Using Artificial Neural Network

Xiuping Li and Jianjun Gao

An approach for the PAD modeling technique for microwave on wafer measurement based on a combination of the conventional equivalent circuit model and artificial neural network (ANN) is presented in this paper. The PAD capacitances are determined from S parameters of different size of PAD test structure based on EM (electromagnetic) simulation and described as functions of the dimensions of the PAD structure by using sub-ANN. Good agreement is obtained between ANN-based modeling and EM simulated results up to 40 GHz. The de-embedding procedure for PHEMT device utilizing the ANN based PAD model is demonstrated.

2007-05-10 PIER Vol. 74, 157-166, 2007. doi:10.2528/PIER07050401

Soliton Based Optical Communication

Ramgopal Gangwar, Sunil Singh, and Nar Singh

The group velocity dispersion (GVD) imposes severe limit on information carrying capacity of optical communication systems. By choosing appropriate pulse shape highly stable light pulses known as solitons are generated when effect of GVD is balanced by self-phase modulation (SPM). The application of solitons in communication systems opens the way to ultrahigh-speed information superhighways. Transmission speed of order of Tbit/s can be achieved if optical amplifiers are combined with WDM in soliton based communication systems.

2007-05-10 PIER Vol. 74, 141-155, 2007. doi:10.2528/PIER07042501

Frequency Selective Structures with Stochastic Deviations

Anders Karlsson, Daniel Sjöberg, and Björn Widenberg

This paper deals with the performance of frequency selective structures with defects. A frequency selective structure is in this case a periodic pattern of apertures in a conducting plate. The plate can be of arbitrary thickness. The defects can be due to deviations in the placing of the apertures, in the material parameters, or in the shape of the apertures. First, the perturbation to the farfield pattern from a deviation in one aperture is analyzed. It is then shown how this affects the mean scattered power from the structure. Numerical illustrations of the perturbed fields on the structure are given.

2007-05-07 PIER Vol. 74, 131-140, 2007. doi:10.2528/PIER07042302

Wideband X-Band Microstrip Butler Matrix

Jun He, Bing-Zhong Wang, Qing-Qiang He, Yu-Xia Xing, and Zhong-Liang Yin

This paper presents the design of a wideband X-band microstrip 4×4Butler matrix. The wideband performance of the Butler matrix means that it possesses equal coupling and difference of phases throughout the operating band. Design of the wideband components such as 3-branch branch line hybrid, crossover and Schiffman line phase shifter are presented in this paper. A final design of the Butler matrix is proposed. The Butler matrix exhibits couplings and phase errors within −6.7 ± 0.7 dB and 10 over a 20% bandwidth with a center frequency at 10 GHz.

2007-05-05 PIER Vol. 74, 113-130, 2007. doi:10.2528/PIER07041506

A Stable Integral Equation Solver for Electromagnetic Scattering by Large Scatterers with Concave Surface

Mei Song Tong

Electromagnetic scattering by electrically large scatterers usually requires a large number of unknowns. To reduce the matrix size, one expects to choose a small sampling rate for the unknown function. In the method of moments (MoM) scheme, this rate is about 10 unknowns per wavelength for electrically small or medium scatterers. However, this rate may not work well for electrically large scatterers with a concave surface. The concave area on the scatter is observed to be the oscillatory part in the solution domain. The oscillation property requires more samplings to eliminate the numerical noises. The multiscalets with a multiplicity of two are higher-order bases. It is shown that the multiscalets are more suitable to represent the unknown function with oscillatory characteristic. Furthermore, the testing scheme under the discrete Sobolev-type inner product allows the MoM have the derivative sampling which enhances the tracking quality of the multiscalets further. Numerical Examples of scattering by 1000 and 1024 wavelength 2D scatterers demonstrate that the use of multiscalets in the MoM can keep the same discretization size for electrically large scatterers as for electrically small scatterers without losing the accuracy of the solution. In contrast, the traditional MoM and Nyström method require the finer discretization scheme if achieving a stable solution.

2007-05-03 PIER Vol. 74, 85-112, 2007. doi:10.2528/PIER07041905

Study on Shielding Effectiveness of Metallic Cavities with Apertures by Combining Parallel FDTD Method with Windowing Technique

Ji-Zhao Lei, Chang-Hong Liang, and Yu Zhang

A novel hybrid method combining 3D Parallel Finite- Difference Time-Domain (FDTD) method with Windowing technique through a new Controlling factor to study the Shielding Effectiveness (SE) of metallic cavities with apertures is firstly presented in this paper. The simulating time when the sampling electric field in cavity converges can be reduced greatly by the MPI-based Parallel FDTD method with the optimum virtual topology for the scattering problem. And then the sampling electric field in cavity is dealt with Windowing technique,whic h can further reduce the total time steps that Parallel FDTD method needs. The numerical results show that combination of Parallel FDTD with Windowing technique can enhance the simulating efficiency greatly. Finally,the SE of metallic cavities with different configurations is studied by the hybrid method and some useful conclusions to the practical electromagnetic shielding problems are obtained.

2007-05-03 PIER Vol. 74, 69-84, 2007. doi:10.2528/PIER07041602

Characterization of Perfectly Conducting Targets in Resonance Domain with Their Quality of Resonance

Janic Chauveau, Nicole de Beaucoudrey, and Joseph Saillard

In resonance domain, the radar scattering response of any object can be modelled by natural poles of resonance with the formalism of the Singularity Expansion Method. The mapping of these poles in the complex plane gives useful information for the discrimination of a radar target, as its general shape, its characteristic dimension and its constitution. In this paper, we use an analogy with resonant circuits modelling to define the quality factor Q of each resonance. Therefore, we propose to characterize the resonance behavior of perfectly conducting targets with this quality factor Q and the natural pulsation of resonance ω0. Indeed, this new representation in {ω0;Q} allows to better separate information than the usual mapping of natural poles of resonance in the complex plane. For perfectly conducting canonical and complex shape targets, we present results exhibiting advantages of these two parameters {ω0;Q}.

2007-05-01 PIER Vol. 74, 57-67, 2007. doi:10.2528/PIER07042101

Analysis of Longitudinally Inhomogeneous Waveguides Using the Method of Moments

Mohammad Khalaj-Amirhosseini

A new method is introduced to analyze arbitrary Longitudinally Inhomogeneous Waveguides (LIWs). In this method, the integral equations of the LIWs, converted from their differential equations, are solved using the method of moments (MOM). It is assumed that the electric permittivity function is known at all or only at some points along the length of LIWs. The validity of the method is verified using a comprehensive example.

2007-05-01 PIER Vol. 74, 47-56, 2007. doi:10.2528/PIER07041904

On the Equivalent Radius of a Radiating Slot in Impedance Calculations

Ashish Tiwari, Dipak Poddar, and Biswanath Das

By means of evaluating impedance of a slot by spectral domain analysis, the radius of the equivalent cylindrical dipole is found in terms of slot parameters. The analysis proceeds from the integral equation for the surface current density induced on a planar strip. Explicit expressions for real and imaginary parts of impedances are derived in visible and invisible regions respectively.

2007-04-25 PIER Vol. 74, 39-46, 2007. doi:10.2528/PIER07041801

Wideband Cavity-Backed Patch Antenna for PCS/IMT2000/2.4 GHz WLAN

Fa Wang and Jin-Sheng Zhang

A wideband cavity-backed patch antenna is presented for operating at PCS, IMT200, and 2.4 GHz WLAN bands. A parasitic patch and a probe with a capacitor patch is used to enhance the bandwidth. The cavity-backed and without cavity-backed antenna has been compared. It has been found that the cavity backed antenna has wide impedance bandwidth of 43% and high gain level. It can simultaneously serve most of the modern wireless communication applications that operate at 1.7 GHz-2.5 GHz.

2007-04-25 PIER Vol. 74, 21-38, 2007. doi:10.2528/PIER07041401

Optimal Design of Dualband CPW-Fed g -Shaped Monopole Antenna for WLAN Application

Wen-Chung Liu

A dualband coplanar waveguide (CPW)-fed planar monopole antenna suitable for WLAN application is presented in this paper. The antenna resembling as a "G" shape and optimally designed by using the particle swarm optimization (PSO) algorithm can produce dual resonant modes and a much wider impedance bandwidth for the higher band. Prototypes of the obtained optimized antenna have been constructed and tested. The measured results explore good dualband operation with −10 dB impedance bandwidths of 9.7% and 62.8% at bands of 2.43 and 4.3 GHz, respectively, which cover the 2.4/5.2/5.8 GHz WLAN operating bands, and show good agreement with the numerical prediction. Also, good antenna performances such as radiation patterns and antenna gains over the operating bands have been observed.

2007-04-23 PIER Vol. 74, 1-19, 2007. doi:10.2528/PIER07032703

Analysis of Interaction Between a Crystallographically Uniaxial Ferrite Resonator and a Hall-Effect Transducer

Marina Koledintseva and Alexander Kitaitsev

In this paper, a number of physical phenomena taking place at the interaction of a crystallographically uniaxial ferrite resonator (UFR) with a semiconductor element, such as a Hall-effect transducer (HET), are analyzed. The UFR in this study is in a direct contact with an unpackaged HET. The interaction is studied in the vicinity of the ferromagnetic resonance in the UFR. The analytical model based on the combination of the problem of interaction of an arbitrarily orientated and shaped UFR with electromagnetic field of a multimode transmission line (waveguide) and thermal balance equations is proposed. A number of thermo/electro/magnetic phenomena that cause a voltage additional to that of the Hall-effect in the HET are analyzed. It is shown that this additional voltage is mainly due to Nernst-Ettingshausen thermo-magnetic effect. Some experimental results in 8-mm waveband are presented. This structure may serve as a frequency-selective primary transducer for detection and measurement of microwave (or millimeter-wave) power.