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2010-05-07
PIER
Vol. 103, 419-431, 2010
download: 704
Pencil Beam Patterns Obtained by Planar Arrays of Parasitic Dipoles Fed by Only One Active Element
Marcos Alvarez Folgueiras Juan Antonio Rodríguez-Gonzalez Francisco Ares-Pena
In this paper, an innovative method for obtaining a pencil beam pattern is presented. Planar arrays of parasitic dipoles are used to modify the pattern of an active dipole above a ground plane, in order to obtain a pencil beam of moderate gain and bandwidth. Only one feed point and one active element provides a very simple feeding network that reduces the complexity of the antenna. The correct configuration of the elements of the parasitic arrays allows to obtain the desired pencil beam pattern. Three designs that use parasitic arrays fed by a λ/2-dipole and synthesize pencil beam patterns are shown: 1) an antenna designed at 1.645 GHz and composed by one layer of 49 parasitic elements; 2) an antenna designed at the same frequency but composed by two layers of 49 parasitic elements; 3) an antenna designed at 5 GHz, composed by one layer of 49 parasitic elements, and taking into account the dielectric substrate and teflon screws.
PENCIL BEAM PATTERNS OBTAINED BY PLANAR ARRAYS OF PARASITIC DIPOLES FED BY ONLY ONE ACTIVE ELEMENT
2010-04-29
PIER
Vol. 103, 403-418, 2010
download: 174
Evolution of Transient Electromagnetic Fields in Radially Inhomogeneous Nonstationary Medium
Oleksandr M. Dumin O. O. Dumina Victor A. Katrich
To solve radiation problems in time domain directly the modal representation of transient electromagnetic fields is considered. Using evolutionary approach the initial nonstationary three-dimensional electrodynamic problem is transformed into the problem for one-dimensional evolutionary equations by the construction of the modal basis for electromagnetic fields with arbitrary time dependence in spherical coordinate system. Elimination of the radial components of electrical and magnetic field from Maxwell equation system permits to form the four-dimensional differential operators. It is proved that the operators are self- adjoint ones. The eigen-functions of the operators form the basis. The completeness of the basis is proved by means of Weyl Theorem about orthogonal detachments of Hilbert space. The expansion coefficients of arbitrary electromagnetic field are found from the set of evolutionary equations. The transient electromagnetic field can be found directly without Fourier transform application by means of one-dimensional FDTD method for the medium with dependence on longitudinal coordinate and time or using Laplace transform and wave splitting for the case of homogeneous stationary medium. The above mentioned methods are compared with the three-dimensional FDTD method for the case of the problem of small loop excitation by transient current.
EVOLUTION OF TRANSIENT ELECTROMAGNETIC FIELDS IN RADIALLY INHOMOGENEOUS NONSTATIONARY MEDIUM
2010-04-29
PIER
Vol. 103, 393-401, 2010
download: 183
A Compact Polarization Beam Splitter Based on a Multimode Photonic Crystal Waveguide with an Internal Photonic Crystal Section
Yaocheng Shi
We present the design and simulation of an ultra-compact polarization beam splitter (PBS) by combining a photonic crystal (PhC) multimode waveguide and an internal PhC section. The PhC multimode waveguide is designed to collect the powers reflected by or transmitted through the internal PhC structure which serves as a polarization sensitive scatterer. Plane wave expansion (PWE) method is used to calculate the band structure and the finite-difference time-domain (FDTD) method is employed to obtain the spectrum response. The simulation results show that the present design can give an ultra-compact PBS with high extinction ratio over a broad bandwidth.
A COMPACT POLARIZATION BEAM SPLITTER BASED ON A MULTIMODE PHOTONIC CRYSTAL WAVEGUIDE WITH AN INTERNAL PHOTONIC CRYSTAL SECTION
2010-04-29
PIER
Vol. 103, 371-391, 2010
download: 146
Efficient Determination of the Near-Field in the Vicinity of an Antenna for the Estimation of Its Safety Perimeter
Jaime Laviada-Martinez Yuri Alvarez-Lopez Fernando Las Heras Andres
The following paper deals with the problem of computing a safety perimeter, i.e., where the electromagnetic field due to a radiating system exceeds a certain electromagnetic value. The flexibility of the source reconstruction method (SRM) is employed to compute the fields almost everywhere around the antenna. Techniques for fast computing of the fields in the spectral and spatial domains exploiting the characteristics of the SRM are considered in order to avoid expensive integrations over the sources surface. Results for a logperiodic antenna and a base station antenna for cellular phone systems are shown, and compared with the usual far-field approximation.
EFFICIENT DETERMINATION OF THE NEAR-FIELD IN THE VICINITY OF AN ANTENNA FOR THE ESTIMATION OF ITS SAFETY PERIMETER
2010-04-28
PIER
Vol. 103, 355-370, 2010
download: 149
Radiation Pattern Synthesis for Maximum Mean Effective Gain with Spherical Wave Expansions and Particle Swarm Techniques
Pedro Luis Carro Ceballos J. De Mingo Sanz Paloma García Dúcar
A new Mean Effective Gain (MEG) expression using SphericalWave Expansions (SWE) is presented in order to evaluate the impact of mobile environments on radiating structures. The proposed approach takes into account the pattern polarization and transforms a continuous functional optimization problem into an approximate discrete formulation. It allows to synthesize efficient antenna radiation patterns in terms of the Mean Effective Gain when it is combined with modern heuristic optimization techniques. In addition, antenna performance limits are evaluated by means of certain bounds. These depend on the modal number which is required to describe accurately far fields and depend ultimately on the antenna size. The method estimates the optimum patterns for two different wireless scenarios that are characterized by the statistical probability density functions of incoming waves and particularized in the case of Gaussian statistics. The numerical evaluation has been performed by means of the Particle Swarm Optimization (PSO) technique, which is slightly modified to include a specific constrain and whose parameters have been computed previously by solving a canonical problem. Finally, representative results in outdoor and mixed wireless scenarios are discussed, pointing out some useful consequences in antenna design.
RADIATION PATTERN SYNTHESIS FOR MAXIMUM MEAN EFFECTIVE GAIN WITH SPHERICAL WAVE EXPANSIONS AND PARTICLE SWARM TECHNIQUES
2010-04-28
PIER
Vol. 103, 339-354, 2010
download: 115
Perturbation Method for the Calculation of Losses Inside Conductors in Microwave Structures
Damien Voyer Ronan Perrussel Patrick Dular
A perturbation method based on the decoupling of propagation and diffusion phenomenons is proposed in order to calculate losses in microwave structures. Starting from the first problem in which the conducting regions are not described, a perturbation is calculated by solving a second problem restricted to the vicinity of the conductors; iterations between these problems can be performed when the perturbed solution is not sufficiently accurate. The perturbation approach is however more accurate than a method based on a surface impedance model, without introducing the huge calculations that appear when both conducting region and external medium are described in a single problem. 2D examples are presented using the finite element method and the integral equation method.
PERTURBATION METHOD FOR THE CALCULATION OF LOSSES INSIDE CONDUCTORS IN MICROWAVE STRUCTURES
2010-04-28
PIER
Vol. 103, 323-338, 2010
download: 365
Polar Format Algorithm for Spotlight Bistatic SAR with Arbitrary Geometry Configuration
Jinping Sun Shiyi Mao Guohua Wang Wen Hong
This paper presents an effective Polar Format Algorithm (PFA) for spotlight bistatic synthetic aperture radar (SAR) with arbitrary geometry configuration. Nonuniform interpolation and resampling are adopted when converting raw data from polar coordinates to Cartesian coordinates according to the characteristics of raw data samples in spatial frequency space. Thus, the proposed algorithm avoids both rotation transformation and the calculation of azimuth compensation factor and thereby avoids the corresponding approximate error appeared in the conventional PFA. Meanwhile, the proposed algorithm inherits the character of decomposing 2-D interpolation to two 1-D interpolations from conventional PFA algorithm applied in monostatic SAR imaging. Therefore, the processing flow, computation efficiency and performance of the proposed algorithm are the same as those of conventional PFA for monostatic spotlight SAR. Point target simulations are provided to validate the proposed algorithm.
POLAR FORMAT ALGORITHM FOR SPOTLIGHT BISTATIC SAR WITH ARBITRARY GEOMETRY CONFIGURATION
2010-04-25
PIER
Vol. 103, 305-322, 2010
download: 114
Scattering from Large 3-D Piecewise Homogeneous Bodies through Linear Embedding via Green's Operators and Arnoldi Basis Functions
Vito Lancellotti Bastiaan P. de Hon Antonius G. Tijhuis
We apply the linear embedding via Green's operators (LEGO) method to the scattering by large finite dielectric bodies which contain metallic or penetrable inclusions. After modelling the body by means of LEGO bricks, we formulate the problem via an integral equation for the total incident currents over the boundaries of the bricks. This equation is turned into a weak form by means of the Method of Moments (MoM) and sub-domain basis functions. Then, to handle possibly large MoM matrices, we employ an order-reduction strategy based on: i) compression of the off-diagonal sub-blocks of the system matrix by the adaptive cross approximation algorithm and ii) subsequent compression of the whole matrix by using a basis of orthonormal entire-domain functions generated through the Arnoldi iteration algorithm. The latter leads to a comparatively small upper Hessenberg matrix easily inverted by direct solvers. We validate our approach and discuss the properties of the Arnoldi basis functions through selected numerical examples.
SCATTERING FROM LARGE 3-D PIECEWISE HOMOGENEOUS BODIES THROUGH LINEAR EMBEDDING VIA GREEN'S OPERATORS AND ARNOLDI BASIS FUNCTIONS
2010-04-23
PIER
Vol. 103, 285-303, 2010
download: 124
Electromagnetic Wave Propagation in Chiral h -Guides
Antonio Topa Carlos Paiva Afonso Barbosa
Guided-wave propagation in chiral H-guides is analyzed, using a building-block approach. In a first stage, a 2D chiral parallel-plate waveguide is studied using a frequency dispersion model for the optically active medium, where the constitutive chiral parameter is assumed to be dependent on the gyrotropic parameter. In the second stage, the mode matching technique and the transverse resonance method are used to characterize the 3D structure. A full parametric study is presented for a fixed frequency. The operational and dispersion diagrams for the chiral H-guide are presented. By replacing the common isotropic slab with a chiral slab, chirality provides an extra degree of freedom in the design of new devices.
ELECTROMAGNETIC WAVE PROPAGATION IN CHIRAL H-GUIDES
2010-04-20
PIER
Vol. 103, 271-284, 2010
download: 169
A Novel Approach to the Design of Dual-Band Power Divider with Variable Power Dividing Ratio Based on Coupled-Lines
Zhe Lin Qing-Xin Chu
This paper presents an approach to the design of a novel dual-band power divider with variable power dividing ratio. To achieve dual-band operation, a novel dual-band quarter-wave length transformer based on coupled-lines is proposed, which is used to replace the quarter-wave length transformer in Wilkinson power divider. The proposed dual-band power divider features a simple compact planar structure with wide bandwidth performance for small frequency ratio. Closed-form design equations with one degree of design freedom are derived using even- and odd-mode analysis and transmission line theory. For verification purpose, power dividers operating at 2.4/3.8 GHz with dividing ratios of 2:1 and 1:1 are designed, simulated and measured. The simulated and measured results are in good agreement.
A NOVEL APPROACH TO THE DESIGN OF DUAL-BAND POWER DIVIDER WITH VARIABLE POWER DIVIDING RATIO BASED ON COUPLED-LINES
2010-04-20
PIER
Vol. 103, 259-269, 2010
download: 162
A Double-Printed Trapezoidal Patch Dipole Antenna for UWB Applications with Band-Notched Characteristic
Yan-Sheng Hu Ming Li Guo-Ping Gao Jin-Sheng Zhang Ming-Kun Yang
In this paper, a novel double-printed trapezoidal patch dipole antenna suitable for UWB applications with band-notched characteristic is presented and investigated. The band -notched characteristic is achieved by inserting T-shape slots on the trapezoidal radiating patches. The impedance characteristic, radiation patterns and the transfer function are studied. Experimental results show that the proposed antenna covers the entire UWB band (3.1-10.6 GHz) while it has a notched band for the IEEE 802.11a frequency band (5.15-5.825 GHz). Measured group delay, transmission characteristics and Time domain characteristics indicate that the proposed antenna satisfies the requirement of the current wireless communications systems.
A DOUBLE-PRINTED TRAPEZOIDAL PATCH DIPOLE ANTENNA FOR UWB APPLICATIONS WITH BAND-NOTCHED CHARACTERISTIC
2010-04-19
PIER
Vol. 103, 241-257, 2010
download: 330
SPICE Models for Radiated and Conducted Susceptibility Analyses of Multiconductor Shielded Cables
Haiyan Xie Jianguo Wang Ruyu Fan Yinong Liu
This paper presents SPICE models to analyze the radiated and conducted susceptibilities of multiconductor shielded cables in the time and frequency domains. These models, which can be used directly in the time and frequency domains, take into account the presence of both the transfer impedance and admittance, and allow the transient analysis when the termination is nonlinear or time-varying. The radiated and conducted susceptibilities are studied by using an incident plane-wave electromagnetic field and an injection current on the cable shield as the source, respectively. Results obtained by these models are in good agreement with those obtained by other methods.
SPICE MODELS FOR RADIATED AND CONDUCTED SUSCEPTIBILITY ANALYSES OF MULTICONDUCTOR SHIELDED CABLES
2010-04-19
PIER
Vol. 103, 217-240, 2010
download: 115
Hybrid FD-FD Analysis of Crossing Waveguides by Exploiting Both the Plus and the Cross Structural Symmetry
Hung-Wen Chang Yan-Huei Wu Wei-Chi Cheng
We propose a hybrid finite-difference frequency-domain method to study the perpendicular crossing waveguide, dielectric and microwave, TE and TM modes, by exploiting built-in structural symmetries in these waveguide devices. In the plus (+) symmetry model, the complete solution is obtained by solving two rectangular-shaped quarter structures each with two transparent boundaries and two symmetry boundaries. For the cross (x) symmetry model, solutions of four triangular-shaped quarter structures are needed but each with only one transparent boundary. Numerical results are verified by comparison between these two models and with the power conservation test. We show the total and the fundamental-mode, coupling coefficients of the reflected, cross and through power in the crossing waveguide as functions of the normalized frequency.
HYBRID FD-FD ANALYSIS OF CROSSING WAVEGUIDES BY EXPLOITING BOTH THE PLUS AND THE CROSS STRUCTURAL SYMMETRY
2010-04-17
PIER
Vol. 103, 201-216, 2010
download: 257
DOA Estimation with Sub-Array Divided Technique and Interporlated ESPRIT Algorithm on a Cylindrical Conformal Array Antenna
Peng Yang Feng Yang Zai-Ping Nie
A novel DOA finding method for conformal array applications is proposed. By using sub-array divided and interpolation technique, ESPRIT-based algorithms can be used on conformal arrays for 1-D and 2-D DOA estimation. In this paper, the circular array mounted on a metallic cylindrical platform is divided to several sub-arrays, and each sub-array is transformed to virtual uniform linear array or virtual uniform planar array through interpolation technique. 1-D and 2-D direction of arrivals can be estimated accurately and quickly by using LS-ESPRIT and 2-D DFT-ESPRIT algorithms, respectively. This method can be applied not only to cylindrical conformal array but also to any other arbitrary curved conformal arrays. Validity of this method is proved by simulation results.
DOA ESTIMATION WITH SUB-ARRAY DIVIDED TECHNIQUE AND INTERPORLATED ESPRIT ALGORITHM ON A CYLINDRICAL CONFORMAL ARRAY ANTENNA
2010-04-16
PIER
Vol. 103, 185-199, 2010
download: 117
Improved 3-D GPR Detection by NUFFT Combined with MPD Method
Yueqin Huang Yanhui Liu Qing Huo Liu Jianzhong Zhang
A combined method of the non-uniform fast fourier transform (NUFFT) migration and the least-square based matching pursuit decomposition (MPD) algorithms is proposed to obtain better discrimination and interpretation for subsurface from ground penetrating radar (GPR) signals. By using the modified NUFFT migration algorithm, a fast and high resolution GPR reconstruction can be obtained with an additional reduction in storage and computation requirements. By incorporating the MPD algorithm into a migration method, denoised reconstructions are obtained to enhance objects detection, including the identification of objects' geometries and the estimation of their sizes and locations. Several examples from synthetic data and field data are demonstrated to establish the effectiveness of the synergic effect by comparing it with the conventional migration methods.
IMPROVED 3-D GPR DETECTION BY NUFFT COMBINED WITH MPD METHOD
2010-04-16
PIER
Vol. 103, 169-184, 2010
download: 357
Properties of Defect Modes in One-Dimensional Photonic Crystals
Chien-Jang Wu Zheng-Hui Wang
A theoretical analysis of the properties of the defect modes in a one-dimensional defective photonic crystal (PC) is given. Two defective PCs stacked in symmetric and asymmetric geometries are considered. The defect modes are investigated by the calculated wavelength-dependent transmittance for both TE and TM waves. It is found that there exists a single defect mode within the photonic band gap (PBG) in the asymmetric PC. There are, however, two defect modes within the PBG in the symmetric one. The dependences of defect modes on the angle of incidence are illustrated. Additionally, the effect of defect thickness on the number of defect modes is also examined.
PROPERTIES OF DEFECT MODES IN ONE-DIMENSIONAL PHOTONIC CRYSTALS
2010-04-15
PIER
Vol. 103, 153-168, 2010
download: 106
Channel-Ranked Beamformer for the Early Detection of Breast Cancer
Martin O'Halloran Martin Glavin Edward Jones
Confocal Microwave Imaging (CMI) for the early detection of breast cancer is based on several assumptions regarding the dielectric properties of normal and malignant breast tissue. One of these assumptions is that the breast is primarily dielectrically homogeneous, and that the propagation, attenuation and phase characteristics of normal breast tissue allows for the constructive addition of the UWB returns from dielectric scatterers within the breast. However, recent studies by Lazebnik et al. have highlighted a very signicant dielectric contrast between normal adipose and broglandular tissue within the breast. This dielectric heterogeneity presents a considerably more challenging imaging scenario, where constructive addition of the UWB returns, and therefore tumor detection, is much more dicult. In a dielectrically homogeneous breast, each additional beamformed backscattered signal adds coherently with existing signals, resulting in an improved image of any dielectric scatterers present. However, in a dielectrically heterogeneous breast, signals with a longer propagation distance are more likely to encounter heterogeneity and therefore are more prone to incoherent addition, reducing the overall quality of the breast image. In this paper, a novel beamforming algorithm is described, which gives extra weighting to signals with shorter propagation distances to create an improved image of the breast. The beamformer is shown to provide improved images of more dielectrically heterogeneous breasts than the traditional delay and sum beamformer from which it is derived.
CHANNEL-RANKED BEAMFORMER FOR THE EARLY DETECTION OF BREAST CANCER
2010-04-15
PIER
Vol. 103, 139-152, 2010
download: 109
Semi-Infinite Chiral Nihility Photonics: Parametric Dependence, Wave Tunneling and Rejection
Vladimir Tuz Cheng-Wei Qiu
The novel characteristics of wave transmission and reflection in one-dimensional semi-infinite chiral photonics have been investigated theoretically. Waves in each region have been formulated for both normal and oblique incidences. At a given incident angle, the transmission or reflection is found to be easily adjusted to be equal to 1 for the chiral photonics using chiral nihility media. The wave tunneling and rejection properties in chiral nihility photonics, as well as their parametric dependences on periodicity, chiral nihility and incident angles, have been explicitly presented theoretically and verified numerically.
SEMI-INFINITE CHIRAL NIHILITY PHOTONICS: PARAMETRIC DEPENDENCE, WAVE TUNNELING AND REJECTION
2010-04-14
PIER
Vol. 103, 115-138, 2010
download: 132
Novel Fractal Antenna Arrays for Satellite Networks: Circular Ring Sierpinski Carpet Arrays Optimized by Genetic Algorithms
Katherine Siakavara
A novel fractal antenna-array type is proposed. The design is based on the Sierpinski rectangular carpet concept. However, the generator is a circular ring area, filled with radiating elements, so the higher stages of the fractal development produce large arrays of circular rings which, besides the high directivity, have the advantage of the almost uniform azimuthal radiation pattern, attribute that many applications require. The introduced arrays can operate as direct radiating multi-beam phased arrays and meet the requirements of satellite communications links: high End of Coverage (EOC) directivity, low Side Lobe Level (SLL) and high Career to Interference ratio (C/I). These operational indices were further optimized by a synthesized multi-objective and multi-dimensional Genetic Algorithm (GA) which, additionally, gave arrays no more than 120 elements.
NOVEL FRACTAL ANTENNA ARRAYS FOR SATELLITE NETWORKS: CIRCULAR RING SIERPINSKI CARPET ARRAYS OPTIMIZED BY GENETIC ALGORITHMS
2010-04-13
PIER
Vol. 103, 101-114, 2010
download: 112
Polarization-Tunable Negative OR Positive Refraction in Self-Complementariness-Based Extraordinary Transmission Prism
Miguel Navarro-Cia Miguel Beruete Francisco J. Falcone Mario Sorolla Ayza Igor Campillo
Here we report a prism made of stacked quasi-selfcomplementary extraordinary transmission surfaces which allows simultaneously left- and right-handed propagation within the V-band for vertical and horizontal polarizations, respectively and righthanded propagation within the W-band for both polarizations. The numerical dispersion diagram of the infinite structure and effective indexes of refraction retrieved from S-parameters under normal incidence together with the finite integration time domain simulations predict single negative and double positive birefringence. The unusual type of birefringence single negative and regular double positive birefringence are afterwards demonstrated experimentally at the millimeter-waves (V- and W-bands) by the wedge experiment which lets us check, using a straightforward geometrical method, the refraction of each component. The effective index of refraction is retrieved via the Snell's law and compared to those obtained through the dispersion diagram and the retrieval method from S-parameters computed with the commercial software CST Microwave StudioTMTM.
POLARIZATION-TUNABLE NEGATIVE OR POSITIVE REFRACTION IN SELF-COMPLEMENTARINESS-BASED EXTRAORDINARY TRANSMISSION PRISM