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2008-04-24
PIER
Vol. 82, 433-445, 2008
download: 593
An Equivalent Circuit Modeling Method for Ultra-Wideband Antennas
Yong Wang Jiazi Li Li-Xin Ran
This paper presents an effective modeling methodology for Ultra-wideband (UWB) antennas. The methodology is based on augmenting an existing narrow-band model with a macro-model while simultaneously perturbing component values of the narrow-band model. The narrow-band model is an empirical-based circuit and the macro-model described by rational functions is determined using data fitting approaches. The perturbation of component values of the narrow-band model is achieved by adjustments in SPICE. This method is demonstrated on the example of a 2.5 cm dipole antenna and a circular disc monopole antenna for UWB systems. Simulation results show that this methodology is effective over a wide bandwidth and suitable for modeling most UWB antennas.
AN EQUIVALENT CIRCUIT MODELING METHOD FOR ULTRA-WIDEBAND ANTENNAS
2008-04-24
PIER
Vol. 82, 419-431, 2008
download: 94
On the Target Classification through Wavelet-Compressed Scattered Ultrawide-Band Electric Field Data and ROC Analysis
Senem Makal Ahmet Kizilay Lutfiye Durak
This paper's aim is to classify cylindrical targets from their ultrawide-band radar returns. To calculate the radar returns, image technique formulation is used to obtain the Electric Field Integral Equations (EFIEs). Then, the EFIEs are solved numerically by Method of Moment (MoM). Because of wide frequency range of the ultrawide-band radar signal, the database to be used for target classification becomes very large. To deal with this problem and to provide robustness, wavelet transform is utilized. Application of wavelet transform significantly reduces the size of the database. The coefficients obtained by wavelet transform are used as the inputs of the artificial neural networks (ANNs). Then, the actual performances of the networks are investigated by Receiver Operating Characteristic (ROC) analysis.
ON THE TARGET CLASSIFICATION THROUGH WAVELET-COMPRESSED SCATTERED ULTRAWIDE-BAND ELECTRIC FIELD DATA AND ROC ANALYSIS
2008-04-24
PIER
Vol. 82, 401-418, 2008
download: 2131
Design of Compact Vivaldi Antenna Arrays for UWB See through Wall Applications
Yunqiang Yang Y. Wang Aly Fathy
Two different types of Vivaldi antenna arrays have been designed for UWB see through wall applications. The first is a 16×1 antipodal Vivaldi antenna covering 8-12GHz, and the second is an 8×1 tapered slot antenna for 2-4GHz frequency range. The array elements are optimized to have a compact size and almost constant gain with frequency. Wilkinson power dividers were designed and fabricated to compose the feed network for the Vivaldi antenna arrays. Measured results of the manufactured antipodal and tapered slot Vivaldi antenna arrays are in excellent agreement with the simulated ones, with a gain of more than 13dBi and 12dBi respectively within their respective operating band. The first array is geared towards see through dry wall with high resolution, while the second is designed at lower frequencies to allow see through concrete wall applications. Full arrays were manufactured and connected to multi-throw switches and have been utilized as part of synthetic aperture radar.
DESIGN OF COMPACT VIVALDI ANTENNA ARRAYS FOR UWB SEE THROUGH WALL APPLICATIONS
2008-04-10
PIER
Vol. 82, 381-400, 2008
download: 117
Time Domain Inverse Scattering of a Two-Dimensional Homogenous Dielectric Object with Arbitrary Shape by Particle Swarm Optimization
Chung-Hsin Huang Chien-Ching Chiu Ching-Lieh Li Kuan-Chung Chen
This paper presents a computational approach to the two-dimensional time domain inverse scattering problem of a dielectric cylinder based on the finite difference time domain (FDTD) method and the particle swarm optimization (PSO) to determine the shape, location and permittivity of a dielectric cylinder. A pulse is incident upon a homogeneous dielectric cylinder with unknown shape and dielectric constant in free space andthe scattered fieldis recorded outside. By using the scattered field, the shape and permittivity of the dielectric cylinder are reconstructed. The subgridding technique is implemented in the FDTD code for modeling the shape of the cylinder more closely. In order to describe an unknown cylinder with arbitrary shape more effectively, the shape function is expandedb y closedcubicspline function insteadof frequently used trigonometric series. The inverse problem is resolved by an optimization approach, and the global searching scheme PSO is then employedto search the parameter space. Numerical results demonstrate that, even when the initial guess is far away from the exact one, good reconstruction can be obtained. In addition, the effects of Gaussian noise on the reconstruction results are investigated. Numerical results show that even the measured scattered E fields are contaminated with some Gaussian noise, PSO can still yield good reconstructed quality.
TIME DOMAIN INVERSE SCATTERING OF A TWO-DIMENSIONAL HOMOGENOUS DIELECTRIC OBJECT WITH ARBITRARY SHAPE BY PARTICLE SWARM OPTIMIZATION
2008-04-09
PIER
Vol. 82, 367-380, 2008
download: 599
Sum and Difference Multiple Beam Modulation Transmitted by Multimode Horn Antenna for Inverse Monopulse Direction-Finding
Maozhong Song Tao Hong
The sum and difference multiple channels were usually applied to the monopulse system only in a receiver. But this paper presents a technique of multiple beam modulation transmitted by the sum and difference multiple channels. The modulated field is designed as three chip signal vectors whose sum and whose differences are controlled by the gains of antennas,and the angle between the sum vector and the differential vector depends on the phase error between the channels so that the different microwave signals can be transmitted in the different directions. A receiver with single-antenna can extract azimuth and elevation with respect to the transmitter. Simulation results show that the proposed modulation system has been successfully designed to integrate digital communication with direction-finding in the way of the reverse monopulse.
SUM AND DIFFERENCE MULTIPLE BEAM MODULATION TRANSMITTED BY MULTIMODE HORN ANTENNA FOR INVERSE MONOPULSE DIRECTION-FINDING
2008-04-09
PIER
Vol. 82, 351-366, 2008
download: 86
Lateral Displacement of an Electromagnetic Beam Reflected from a Grounded Indefinite Uniaxial Slab
Fanmin Kong Bae-Ian Wu Hui Huang Jiangtao Huangfu Sheng Xi Jin Au Kong
A theoretical analysis of the lateral shift for an electromagnetic beam reflected from an uniaxial anisotropic slab coated with perfect conductor is presented. The analytic expression for the lateral shift is derived by using the stationary-phase approach, and the conditions for negative and positive lateral shifts are discussed. It is shown that the lateral shift depends not only on the slabthic kness and the incident angle, but also on the constitutive parameters of the uniaxial medium. Enhancement and suppression of lateral shift are observed and are attributed to the interference between the reflected waves from the two interfaces of the slab. By tuning the thickness of the slaband material parameters, large negative and positive shifts can be attained. In particular, when total reflection occurs at the upper interface, the lateral shift will saturate with increasing slabthic kness.
LATERAL DISPLACEMENT OF AN ELECTROMAGNETIC BEAM REFLECTED FROM A GROUNDED INDEFINITE UNIAXIAL SLAB
2008-04-09
PIER
Vol. 82, 333-350, 2008
download: 121
Experimental Validation of a Hybrid Wide-Angle Parabolic Equation - Integral Equation Technique for Modeling Wave Propagation in Indoor Wireless Communications
Giorgos Theofilogiannakos Traianos V. Yioultsis Thomas Xenos
A new full-wave Parabolic --- Integral Equation Method (PE-IEM) for the simulation of wave propagation in realistic, highly complex indoor communication environments is proposed, together with an extensive validation via measurements. The method is based on a wide-angle parabolic equation, further enhanced by an integral equation correction and is capable of providing good approximations of the electromagnetic fields and the received power, incorp orating all fundamental propagation mechanisms in a single simulation. For a rigorous validation, it has been applied in a complex twelve-room office space and compared with measurements at the two different frequencies of 1 GHz and 2.5 GHz. The accuracy of the approximation is within reasonably expected margins, while the method retains all the advantages of full wave methods and it also has moderate requirements of computational resources.
EXPERIMENTAL VALIDATION OF A HYBRID WIDE-ANGLE PARABOLIC EQUATION - INTEGRAL EQUATION TECHNIQUE FOR MODELING WAVE PROPAGATION IN INDOOR WIRELESS COMMUNICATIONS
2008-04-09
PIER
Vol. 82, 319-332, 2008
download: 149
An Improved Particle Swarm Optimization Algorithm for Pattern Synthesis of Phased Arrays
Wen-Tao Li Xiao-Wei Shi Yong-Qiang Hei
In this paper an improved particle swarm optimization algorithm (IPSO) for electromagnetic applications is proposed. In order to overcome the drawbacks of standard PSO, some improved mechanisms for velocity updating, the exceeding boundary control, global best perturbation and the simplified quadratic interpolation (SQI) operator are adopted. To show the effectiveness of the proposed algorithm, a selected set of numerical examples, concerned with linear as well as planar array, is presented. Simulation results show that the refined pinpointing search ability and the global search ability of the proposed algorithm are significantly improved when compared to the particle swarm optimization (PSO) and Genetic Algorithm (GA).
AN IMPROVED PARTICLE SWARM OPTIMIZATION ALGORITHM FOR PATTERN SYNTHESIS OF PHASED ARRAYS
2008-04-08
PIER
Vol. 82, 299-318, 2008
download: 97
Morphological Processing of Electromagnetic Scattering Data for Enhancing the Reconstruction Accuracy of the Iterative Multi-Scaling Approach
Davide Franceschini Massimo Donelli Paolo Rocca Manuel Benedetti Andrea Massa Matteo Pastorino
This work is aimed at presenting a methodology that exploits the scattered electromagnetic radiation collected on a measurement region outside the area under investigation to locate and characterize multiple unknown profiles. In many practical cases, an accurate quantitative imaging of the scenario under test is required and it can be reached by using a high resolution representation of the dielectric profile of the scatterers. Towards this aim, an enhanced iterative multi-resolution procedure that exploits a morphological processing for detecting and focusing on different non-connected regions-of-interest is developed. A suitable set of representative numerical results is presented for demonstrating that the proposed approach is able to efficiently detect the objects located in the test domain and to enhance the accuracy in reconstructing multiple scatterers.
MORPHOLOGICAL PROCESSING OF ELECTROMAGNETIC SCATTERING DATA FOR ENHANCING THE RECONSTRUCTION ACCURACY OF THE ITERATIVE MULTI-SCALING APPROACH
2008-04-04
PIER
Vol. 82, 287-298, 2008
download: 109
The Effect of Microwave Emmision from Mobile Phones on Neuron Survival in Rat Central Nervous System
Yongjian Zhu Feng Gao Xiaofeng Yang Hong Shen Weiguo Liu Hongsheng Chen Xiuyi Jiang
To investigate the effect of microwave emitted by mobile phones on the rat central nervous system (CNS), in vitro cultured cortical neuronal cells and in vivo rat's brain were exposed to the electromagnetic waves emitted by a microwave transmitter that mimics the working frequency of mobile phones. Trypan blue staining and terminal deoxynucleotidy transferase-mediated dUTP nick-end labeling (TUNEL) were used to determine the survival state of neuronal cells while immunohistochemistry method was used to determine the expression level of Bcl-2 and Bax. Our results show that microwave lead to significant cell death in culture and more in vivo brain neuronal cells were stained positive for TUNEL, Bax and Bcl-2 in rats with cranial defect after exposure than that for control groups (with intact cranium, or had no microwave exposure) (P < 0.01). However, no significant differences were observed in the ratio of Bax/Bcl-2 among the groups studied. Therefore, microwave emitted from mobile phones is harmful to both in vitro cultured cortical cells and in vivo brain neuronal cells from rat with cranial defect. The integrity of cranium is important in protecting the CNS against apoptotic injuries inflicted by the microwaves from mobile phones.
THE EFFECT OF MICROWAVE EMMISION FROM MOBILE PHONES ON NEURON SURVIVAL IN RAT CENTRAL NERVOUS SYSTEM
2008-04-02
PIER
Vol. 82, 271-285, 2008
download: 137
Trapped Surface Wave and Lateral Wave in the Presence of a Four-Layered Region
Yi Hui Xu Wang Ren Liang Liu Kai Li
In this paper, propagation model considers the region as a perfect conductor, covered by the two layer dielectrics, and air above. Propagation of the electromagnetic field in the presence of a four-layered region is examined in detail when a vertical electric dipole and observation point are located in the air. Similar to the three-layered case, analytical results are found for the electromagnetic field, which includes four wave modes: a direct wave,an ideal reflected wave, trapped surface waves, and lateral waves. The wave number of the trapped surface wave, which is contributed by the sums of residues of the poles, is between the wave numbers k0 in the air and k2 in the lower dielectric layer. The lateral wave is evaluated by the integrations along the branch cut. Analysis and computations shows that the trapped surface wave play a major role in communication at large distance when both the source point and observation point are on or close to the boundary between the air and the upper dielectric layer.
TRAPPED SURFACE WAVE AND LATERAL WAVE IN THE PRESENCE OF A FOUR-LAYERED REGION
2008-03-30
PIER
Vol. 82, 257-270, 2008
download: 113
Analysis of the Surface Magnetoplasmon Modes in the Semiconductor Slit Waveguide at Terahertz Frequencies
Fanmin Kong Kang Li Hui Huang Bae-Ian Wu Jin Au Kong
The propagation properties of surface plasmon polaritons (SPP) modes and surface magnetoplasmon polaritons (SMP) modes in a semiconductor slit waveguide are analyzed by the effective dielectric constant approach, and the interaction of the external magnetic field with the dispersion properties and field distributions of SMP modes in the Voigt configuration are emphasized in our analysis. Both the symmetric structure and the asymmetric structure are discussed in details. In contrast to the SPP modes which have one propagation band below the plasmon frequency only, the SMP modes have both the low-frequency propagation band below the plasmon frequency and the high-frequency propagation band above the plasmon frequency. When the external magnetic field increases, the two bands of the SMP modes will separate further in frequency, and the even symmetric distribution of the fundamental mode, which usually associates with the SPP mode, will be destroyed. These results can provide some guidance for the design of the tunable semiconductor waveguide in the terahertz regime.
ANALYSIS OF THE SURFACE MAGNETOPLASMON MODES IN THE SEMICONDUCTOR SLIT WAVEGUIDE AT TERAHERTZ FREQUENCIES
2008-03-30
PIER
Vol. 82, 241-255, 2008
download: 100
Efficient Electrically Small Prolate Spheroidal Antennas Coated with a Shell of Double-Negative Metamaterials
Ming Da Huang Soon Yim Tan
An efficient, electrically small prolate spheroidal antenna coated with confocal double-negative (DNG) metamaterials (MTMs) shell is presented. The radiation power of this antenna-DNG shell system excited by a delta voltage across an infinitesimally narrow gap around the antenna center is obtained using the method of separation of the spheroidal scalar wave functions. Our results show that this electrically small dipole-DNG shell system has very high radiation efficiency comparing with the normal electrically small antenna due to the inductive effect of the MTMs shell that cancel with the capacitive effect of the electrically small antenna. It is found that the spheroidal shell can achieve more compact structure and higher radiated power ratio than the corresponding spherical shell. This dipole-DNG shell systems with different sizes are analyzed and discussed.
EFFICIENT ELECTRICALLY SMALL PROLATE SPHEROIDAL ANTENNAS COATED WITH A SHELL OF DOUBLE-NEGATIVE METAMATERIALS
2008-03-30
PIER
Vol. 82, 227-240, 2008
download: 134
Tracking Airborne Targets Hidden in Blind Doppler Using Current Statistical Model Particle Filter
Zhi-Guo Shi Shao-Hua Hong Kang Chen
This paper aims at finding an algorithm featuring good estimation performance and easy hardware implementation for tracking airborne target hidden in blind Doppler. Incorporating the current statistical model which is effective in dealing with the maneuvering motions that most blind Doppler issues are caused, a current statistical model particle filter (CSM-PF) is presented in this paper for tracking airborne targets hidden in blind Doppler. Simulation results demonstrate that the proposed CSM-PF shows similar performance with the interacting multiple model particle filter (IMM-PF) in terms of tracking accuracy and track continuity, but it avoids the difficulty of model selection for maneuvering targets. In addition, when hardware implementation is considered, the proposed CSM-PF has lower processing latency, fewer resource utilization and lower hardware complexity than the IMM-PF.
TRACKING AIRBORNE TARGETS HIDDEN IN BLIND DOPPLER USING CURRENT STATISTICAL MODEL PARTICLE FILTER
2008-03-26
PIER
Vol. 82, 203-226, 2008
download: 225
The Methods of External Excitation for Analysis of Arbitrarily-Shaped Hollow Conducting Waveguides
Sergiy Reutskiy
A new numerical technique is proposed for analyzing arbitrary shaped hollow waveguides. The method is based on mathematically modelling of physical response of a system to excitation over a range of frequencies. The response amplitudes are then used to determine the resonant frequencies. The results of the numerical experiments justifying the method are presented. The method is validated by circular waveguide,rectangular waveguide an equilateral triangular waveguide. We apply the method for multi connected domains and for waveguides with boundary singularities like the Lshaped waveguide. Good agreements between the simulated and the published results have been obtained. The method does not generate spurious eigenfrequencies.
THE  METHODS OF EXTERNAL  EXCITATION FOR ANALYSIS OF ARBITRARILY-SHAPED HOLLOW CONDUCTING WAVEGUIDES
2008-03-25
PIER
Vol. 82, 189-202, 2008
download: 148
Transient Analysis of Microstrip – Like Interconnections Guarded by Ground Tracks
Rohit Y. Sharma Tapas Chakravarty A. Bhushan Bhattacharyya
Guarded ground tracks are extensively used in high density routing for mitigation of crosstalk. However, these ground tracks can influence the electrical properties of the interconnect line also. We present a novel analytical model for extraction of line parameters of high-speed interconnect lines guarded by ground tracks. Based on the proposed model, transient response of such interconnect structures is presented. It is seen ground tracks can significantly affect the time-domain response of the interconnect lines. The computed interconnect circuit parameters are compared with finite-difference time-domain simulations. The proposed model can be practically used for time-domain analysis of microstrip lines also. The results obtained would be useful in design of high-speedin terconnections for MCM, RF and MIC related applications.
TRANSIENT ANALYSIS OF MICROSTRIP – LIKE INTERCONNECTIONS GUARDED BY GROUND TRACKS
2008-03-25
PIER
Vol. 82, 167-188, 2008
download: 90
An Alternative Solution for the Reflector Surface Retrieval Problem
Pietro Bolli Giuseppe Mazzarella Giorgio Montisci Giampaolo Serra
The retrieval of the surface profile of a reflector antenna is an important task, mainly for radio-astronomical applications. The microwave holography retrieves the reflector profile starting from a set of measured far-field data. The main step of this technique is the computation of the induced currents on the reflector surface. This requires the solution of a linear inverse problem which is strongly illconditioned. We propose a new technique, based on the Singular Value Decomposition, for the solution of this linear inversion problem. This technique supplies a flexible regularization scheme, able to take into account also the noise level of the data. The proposed procedure has been tested on a number of different cases, with field data generated by a commercial software.
AN ALTERNATIVE SOLUTION FOR THE REFLECTOR SURFACE RETRIEVAL PROBLEM
2008-03-20
PIER
Vol. 82, 151-166, 2008
download: 100
Compact Broadband Dual-Band Bandpass Filters Using Slotted Ground Structures
Xiao-Hua Wang Bing-Zhong Wang Kevin Chen
Dual-band bandpass filters featuring compact size and flexible frequency choice are demonstrated using resonators based on slotted ground structures. Two resonators based on slotted ground structures form the basis of the filter design. The resonators allow the back-to-back and face-to-face embedding configuration, hence, greatly reduces the physical size of the filters. By changing the sizes of the two resonators independently, the lower and upper resonance frequencies can be adjusted to the desired values. A dual-band broadband bandpass filter was implemented with good compactness and low insertion loss. A good agreement is obtained between the simulation and measurement results.
COMPACT BROADBAND DUAL-BAND BANDPASS FILTERS USING SLOTTED GROUND STRUCTURES
2008-03-20
PIER
Vol. 82, 137-150, 2008
download: 120
Influence of External Magnetic Field on a Symmetrical Gyrotropic Slab in Terms of Goos-h änchen Shifts
Hui Huang Yu Fan Fanmin Kong Bae-Ian Wu Jin Au Kong
A detailed study on the influence of an external magnetic field on a symmetrical gyrotropic slab in terms of Goos-Hanchen (GH) phase shifts is presented. The GH phase shifts at both boundaries of the slab are calculated, and the guidance condition is explained by means of them. It is found that the external magnetic field destroys the spatial symmetry of the field distribution, and we use the concepts of `penetration' distance as well as effective thickness to illustrate the phenomenon. In term of the GH phase shifts, the spatial distribution of the time-average Poynting power is also derived. We find that influenced by the external magnetic field, the positive and negative time-average Poynting power along the waveguide direction can exist simultaneously in the gyrotropic medium, depending on the transverse position.
INFLUENCE OF EXTERNAL MAGNETIC FIELD ON A SYMMETRICAL GYROTROPIC SLAB IN TERMS OF GOOS-HÄNCHEN SHIFTS
2008-03-20
PIER
Vol. 82, 127-136, 2008
download: 168
A Novel UWB Elliptical Slot Antenna with Band-Notched Characteristics
Rajab Fallahi Abdol Aziz Kalteh Mahdi Roozbahani
This paper presents a novel band-notched elliptical slot antenna for Ultra Wide-Band (UWB) communication, which is printed on a dielectric substrate of RT/duroid 6006 with relative permittivity (εr) of 6.0, thickness of 1.27 mm, and fed by an elliptical open ended microstrip line connected to the 50Ω main line. This antenna is designed to be used in frequency band of 3.1-10.6 GHz. Bandnotched characteristics of antenna to reject the frequency band of 5.15-5.825 GHz, which is limited by IEEE 802.11a, is realized by parasitic inverted-U strip attached to the elliptical slot plane. Effects of varying the parameters of parasitic inverted-U strip on performance of proposed antenna have been investigated. The antenna with optimal parameters obtained from parametric study is fabricated and measured. It is observed that the simulation and experimental results have good agreements with each other.
A NOVEL UWB ELLIPTICAL SLOT ANTENNA WITH BAND-NOTCHED CHARACTERISTICS