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2008-04-24
PIER
Vol. 81, 447-459, 2008
download: 579
Application of SVD Noise-Reduction Technique to PCA Based Radar Target Recognition
Kun-Chou Lee Jhih-Sian Ou Ming-Chung Fang
The noise effect is very challenging in radar target recognition. It usually degrades the accuracy of target recognition and then makes the recognition unreliable. In this study, we present a noise-reduction technique to improve the accuracy of radar target recognition. Our noise-reduction technique is based on the SVD (singular value decomposition). The PCA (principal components analysis) based radar recognition algorithm is utilized to verify our noise-reduction scheme. In our treatment, the received signals are arranged into a Hankel-form matrix. This Hankel-form matrix is decomposed into two subspaces, i.e., the noise-related subspace and clean-signal subspace. The noise reduction is obtained by suppressing the noise-related subspace and retaining the clean-signal space only. Simulation results show that the accuracy of target recognition is greatly improved as the received signals are first processed by the SVD noise-reduction technique. With the use of proposed noise-reduction scheme, the radar target recognition can tolerate more noises and then becomes more reliable. The noise-reduction technique in this study can also be applied to many other problems in radar engineering.
APPLICATION OF SVD NOISE-REDUCTION TECHNIQUE TO PCA BASED RADAR TARGET RECOGNITION
2008-02-10
PIER
Vol. 81, 437-446, 2008
download: 164
Directive Emission Obtained by Coordinate Transformation
Jing Jing Zhang Yingliang Luo Sheng Xi Hongsheng Chen Li-Xin Ran Bae-Ian Wu Jin Au Kong
We use coordinate transformation theory to realize substrates that can modify the emission of an embedded source. Simulation results show that with proper transformation functions the energy radiated by a source embedded in these space variant media will be concentrated in a narrow beam. The thickness of the slab achieved with our transformations will no longer be restricted by the evanescent modes and the source can be placed at any position along the boundary of the substrate without affecting the radiation pattern. We also discuss the case where reduced parameters are used,whic h still performs well and is physically realizable.
DIRECTIVE EMISSION OBTAINED BY COORDINATE TRANSFORMATION
2008-02-10
PIER
Vol. 81, 413-436, 2008
download: 120
SPM Numerical Results from an Effective Surface Impedance for a One-Dimensional Perfectly-Conducting Rough Sea Surface
Yohann Brelet Christophe Bourlier
From the analytical theory of rough surface Green's function based on the extension of the diagram method of Bass, Fuks and Itô, with the smoothing approximation, numerical results are presented for Gaussian and sea spectra and compared with a benchmark method by considering a one-dimensional perfectly conducting Gaussian rough surface. The effects of multiple scattering due to the surface roughness are incorporated systematically into the solutions through an effective surface impedance, which can be iterated up to the second-order. In addition, comparisons of the bistatic scattering coefficients are presented with the first- and second- orders conventional small perturbation method. This study will be useful for remote sensing of the ocean surface, especially when the transmitter is close to the surface.
SPM NUMERICAL RESULTS FROM AN EFFECTIVE SURFACE IMPEDANCE FOR A ONE-DIMENSIONAL PERFECTLY-CONDUCTING ROUGH SEA SURFACE
2008-02-06
PIER
Vol. 81, 393-412, 2008
download: 153
Numerical Approach to Survey the Problem of Electromagnetic Scattering from Resistive Strips Based on Using a Set of Orthogonal Basis Functions
Saeed Hatamzadeh Mohammad Naser-Moghadasi Esmail Babolian Zahra Masouri
In this paper, the problem of electromagnetic scattering from resistive strips is solved and discussed. This problem is modeled by the integral equations of the second kind. The basic mathematical concept is collocation method using block-pulse orthogonal basis functions. An effective numerical method for solving these integral equations is proposed. The problem of electromagnetic scattering from resistive strips is treated in detail, the illustrative computations are given for several cases, and an extensive discussion on the obtained results is performed. This method can be generalized to apply to objects of arbitrary geometry.
NUMERICAL APPROACH TO SURVEY THE PROBLEM OF ELECTROMAGNETIC SCATTERING FROM RESISTIVE STRIPS BASED ON USING A SET OF ORTHOGONAL BASIS FUNCTIONS
2008-02-05
PIER
Vol. 81, 371-391, 2008
download: 187
Electromagnetic Field of a Horizontal Electric Dipole in the Presence of a Four-Layered Region
Yi Hui Xu Kai Li Liang Liu
In this paper, we study in detail the electromagnetic field excited by a horizontal electric dipole in the presence of a four-layered region, which consists of a perfect conductor, the two dielectric layers, and air above. From the derivations and analysis, it is seen that the electromagnetic field includes four wave modes: Direct wave, ideal reflected wave, trapped surface wave, and lateral wave. The wave numbers of the trapped surface wave, which are determined by the residues of the poles, are between the wave number k0 in the air and k2 in the lower dielectric layer. The lateral waves with the wave number being k0 are determined by the integrations along the branch cuts. It should be pointed out that both the trapped surface wave and lateral wave can be separated into the electric-type terms and magnetic-type terms. Analysis and computations show that the trapped surface waves play major roles at large propagation distance when both the dipole point and the observation point are on or close to the air-dielectric boundary.
ELECTROMAGNETIC FIELD OF A HORIZONTAL ELECTRIC DIPOLE IN THE PRESENCE OF A FOUR-LAYERED REGION
2008-02-05
PIER
Vol. 81, 359-370, 2008
download: 1097
Chip Impedance Matching for UHF RFID Tag Antenna Design
Chye-Hwa Loo Khaled Elmahgoub Fan Yang Atef Elsherbeni Darko Kajfez Ahmed Kishk Tamer Elsherbeni Leena Ukkonen Lauri Sydanheimo Markku Kivikoski Sari Merilampi Pekka Ruuskanen
Passive UHF RFID tag consists of a microchip attached directly to an antenna. Proper impedance match between the antenna and the chip is crucial in RFID tag design. It directly influences RFID system performance characteristics such as the range of a tag. It is known that an RFID microchip is a nonlinear load whose complex impedance in each state varies with the frequency and the input power. This paper illustrates a proper calculation of the tag power reflection coefficient for maximum power transfer by taking into account of the changing chip impedance versus frequency.
CHIP IMPEDANCE MATCHING FOR UHF RFID TAG ANTENNA DESIGN
2008-02-03
PIER
Vol. 81, 343-357, 2008
download: 109
Investigation of Electromagnetic Complex Scattering for Conductor Target Based on Electromagnetic Images Method
Ying-Le Li Ji-Ying Huang Ming-Jun Wang
The general image relations of electromagnetic sources are presented around a conductor sphere. The general transformations of trigonometric functions and the unit vectors between two coordinates depart from a distance are obtained. The second scattering field for a target is derived in detail. The complex scattering field and the complex RCS are gained respectively. Results show that the electromagnetic interaction of the targets must be calculated as the distance between two targets is small. The second scattering field is small to three order in magnitude to its first scattering field as the distance becomes large. The phase shift of the second field is mainly determined by the target size and the observing position and not affected greatly by its surrounding target and the distance apart. The distortion of a pulse wave is mainly induced by the phase shift of the second scattering field from the particles as the wave propagating through the random discrete medium.
INVESTIGATION OF ELECTROMAGNETIC COMPLEX SCATTERING FOR CONDUCTOR TARGET BASED ON ELECTROMAGNETIC IMAGES METHOD
2008-02-03
PIER
Vol. 81, 329-341, 2008
download: 481
Kd-Tree Based Fast Ray Tracing for RCS Prediction
Yu Bo Tao Hai Lin Hu Bao
Ray tracing is of great use for computational electromagnetics, such as the well-known shooting and bouncing ray (SBR) method. In this paper, the kd-tree data structure, coupled with the mailbox technique, is proposed to accelerate the ray tracing in the SBR. The kd-tree is highly effective in handling the irregularly distribution of patches of the target, while the repeatedly intersection tests between the ray and the patch when using space division acceleration structures can be eliminated through the mailbox technique. Numerical results show excellent agreement with the measured data and the exact solution, and demonstrate that the kd-tree as well as the mailbox technique can greatly reduce the computation time.
KD-TREE BASED FAST RAY TRACING FOR RCS PREDICTION
2008-01-31
PIER
Vol. 81, 315-328, 2008
download: 111
Robust Adaptive Beamforming for a Class of Gaussian Steering Vector Mismatch
Yujie Gu Zhi-Guo Shi Kang Chen Yu Li
Compared with the worst-case optimization-based approach, the probability-constrained approach is a more flexible one to robust adaptive beamforming. In this paper, a precise relationship between the two approaches is built in the case of Gaussian steering vector mismatch, which shows that the probability-constrained beamformer design can be interpreted in terms of the worst-case beamformer design. Numerical simulations demonstrate that the precise version of the probability-constrained beamformer is more robust to the steering vector mismatch than the other popular robust adaptive beamformers.
ROBUST ADAPTIVE BEAMFORMING FOR A CLASS OF GAUSSIAN STEERING VECTOR MISMATCH
2008-01-30
PIER
Vol. 81, 303-314, 2008
download: 186
Adaptively Accelerated GMRES Fast Fourier Transform Method for Electromagnetic Scattering
Yuan Xin Ping-Liang Rui
The problem of electromagnetic scattering by 3D dielectric bodies is formulated in terms of a weak-form volume integral equation. Applying Galerkin's method with rooftop functions as basis and testing functions,the integral equation can be usually solved by Krylov-subspace fast Fourier transform (FFT) iterative methods. In this paper,the generalized minimum residual (GMRES)-FFT method is used to solve this integral equation,and several adaptive acceleration techniques are proposed to improve the convergence rate of the GMRES-FFT method. On several electromagnetic scattering problems,the performance of these adaptively accelerated GMRESFFT methods are thoroughly analyzed and compared.
ADAPTIVELY ACCELERATED GMRES FAST FOURIER TRANSFORM METHOD FOR ELECTROMAGNETIC SCATTERING
2008-01-26
PIER
Vol. 81, 291-302, 2008
download: 136
Multilevel Fast Multipole Algorithm for Radiation Characteristics of Shipborne Antennas Above Seawater
Xun-Wang Zhao Chang-Hong Liang Le Liang
Radiation characteristics of shipborne antennas above lossy half-space are studied using the multilevel fast multipole algorithm (MLFMA). The near terms in the MLFMA are evaluated by using the rigorous half-space dyadic Green's function, computed via the method of complex images. The far MLFMA interactions employ an approximate dyadic Green's function via a direct-radiation term plus a single real image, with the image amplitude characterized by the polarization-dependent Fresnel reflection coefficient. Finally, radiation patterns of an ultra-shortwave antenna mounted on a realistic 3-D ship over seawater are presented and compared with a rigorous method-ofmoments (MoM) solution.
MULTILEVEL FAST MULTIPOLE ALGORITHM FOR RADIATION CHARACTERISTICS OF SHIPBORNE ANTENNAS ABOVE SEAWATER
2008-01-23
PIER
Vol. 81, 279-289, 2008
download: 322
Indoor Accurate RCS Measurement Technique on UHF Band
Chu-Feng Hu Jia-Dong Xu N. J. Li Lin-Xi Zhang
Based on the step-frequency RCS measurement system, high performance absorbers and low scattering supports, employing two log-periodic dipole antennas to carry out the quasi-monostatic measurement and many DSP techniques to reduce the error, the indoor accurate RCS measurement can be completed on UHF band. Experimental results show that the valid data waved less than 1 dB can be obtained over 70% of whole band.
INDOOR ACCURATE RCS MEASUREMENT TECHNIQUE ON UHF BAND
2008-01-23
PIER
Vol. 81, 267-277, 2008
download: 93
Transition Behavior of k -Surface: from Hyperbola to Ellipse
Shan Qiao Guoan Zheng Haifei Zhang Li-Xin Ran
The transition behavior of the k-surface of a lossy anisotropic indefinite slab is investigated. It is found that, if the material loss is taken into account, the k-surface does not show a sudden change from hyperbola to the ellipse when one principle element of the permittivity tensor changes from negative to positive. In fact, after introducing a small material loss, the shape of the k-surface can be a combination of a hyperbola and an ellipse, and a selective high directional transmission can be obtained in such a slab.
TRANSITION BEHAVIOR OF K-SURFACE: FROM HYPERBOLA TO ELLIPSE
2008-01-22
PIER
Vol. 81, 253-265, 2008
download: 137
FDTD Study on Wave Propagation in Layered Structures with Biaxial Anisotropic Metamaterials
Mao-Yan Wang Jun Xu Jian Wu Bing Wei Hai-Long Li Tong Xu De-Biao Ge
The Gaussian beam propagation in multi-layered structures that include indefinite anisotropic metamaterial (AMM) are simulated with shift operator method in Finite-Difference Time-Domain method (FDTD). The excitations of backward and forward surface affected by the types of biaxial AMM are investigated. Numerical results show that the directions of the guided wave excited are influenced by the sign of z component of relative permeability tensor of AMM that determines the energy flow is positively refracted or negatively refracted. Positive or negative Goos-H¨anchen shift associated with Total Cutoff media are also shown.
FDTD STUDY ON WAVE PROPAGATION IN LAYERED STRUCTURES WITH BIAXIAL ANISOTROPIC METAMATERIALS
2008-01-22
PIER
Vol. 81, 237-252, 2008
download: 253
Analysis of Wave Function, Energy and Transmission Coefficients in GaN /AlGaN Superlattice Nanostructures
Kanchan Talele Dyneshwar Patil
Analysis of wave function intensity, eigen energy and transmission coefficients in GaN/AlGaN superlattice nanostructure has been carried out using Transfer Matrix Method (TMM). The effect of change in Aluminum mole fraction in AlxGa1xN barrier region has been included through variable effective mass in the Schrödinger time independent equation. The behaviour of wave function intensity has been studied for superlattice structure by changing the barrier width. The effect of smaller barrier width on wave function intensity in case of superlattice is clearly observed due to interaction of wave functions in the adjacent wells and it provides a new insight in the nature of interacting wave functions for thin barriers in GaN/AlGaN superlattice structures. The barrier widths have been optimized for the varying number of wells leading to better quantum confinement. The iterative method (Secant Method) is used to determine value of electron energy E. The number of iterations need to converge the value of E has been simulated. Transmission coefficients have been determined as a function of energy E considering tunneling effect for three well structures using TMM. Analysis has been extended to show surface image of wave function intensity for 5 and 6 wells.
ANALYSIS OF WAVE FUNCTION, ENERGY AND TRANSMISSION COEFFICIENTS IN GaN/ALGaN SUPERLATTICE NANOSTRUCTURES
2008-01-19
PIER
Vol. 81, 225-235, 2008
download: 115
Design of Photonic Band Gap Filter
Ragini Srivastava Khem Thapa Shyam Pati Sant Ojha
In this paper a new type of optical filter using photonic band gap materials has been suggested. A detailed mathematical analysis is presented to predict allowed and forbidden bands of wavelengths with variation of angle of incidence. It is possible to get desired ranges of the electromagnetic spectrum filtered with this structure by changing the incidence angle of light.
DESIGN OF PHOTONIC BAND GAP FILTER
2008-01-19
PIER
Vol. 81, 213-223, 2008
download: 101
Improved Channel Estimation and MAI-Robust Schemes for Wireless Ofdma System
Y.-D. Lee D.-H. Park Hyoung-Kyu Song
This paper presents an investigation into improving the channel estimation scheme and reducing the effects of symbol timing misalignment when OFDMA is used as an access scheme. Under OFDMA uplink channel environments, appropriate symbol length of CAZAC sequences as a preamble could be utilized in accordance with the number of transmitting antenna and channel condition. The effect of the number of CAZAC sequences for channel estimation is also presented in terms of mean square error (MSE). Taking into account the effect of multiple access interference (MAI) introduced by a symbol timing misalignment, the symbol error rate (BER) and throughput performance are investigated for a typical OFDMA uplink scenario.
IMPROVED CHANNEL ESTIMATION AND MAI-ROBUST SCHEMES FOR WIRELESS OFDMA SYSTEM
2008-01-19
PIER
Vol. 81, 197-212, 2008
download: 98
Numerical Simulation of Propagation of EM Pulse through Lossless Non-Uniform Dielectric Slab Using Characteristic-Based Method
Mingtsu Ho Fu-Shun Lai Shun-Wen Tan Pi-Wei Chen
This paper demonstrates the one-dimensional computational results of the propagation of Gaussian electromagnetic pulse through dielectric slabs of finite thickness with variation in permittivity. The numerical approach used is the characteristic-based method solving the time-domain Maxwell curl equations involved with nonuniform permittivity. In the numerical model, all dielectric slabs are assumed to be isotropic, lossless, and linear. The permittivity of dielectric slab may increase or decrease linearly or sinusoidally. The numerical permittivity is finely discretized such that the variation between two adjacent grids is so small that the non-uniform permittivity is assumed to be piecewise continuous and consequently can be modeled as an individual block. The numerical results of various electric fields, both in the time- and frequency-domain, are presented and compared based on the dielectric slab of constant permittivity for close investigating the effects of the non-uniform permittivity distribution on the electromagnetic fields. It is also shown that under certain arrangement of Gaussian electromagnetic pulse and dielectric slab thickness the pattern of field propagation, reflection and transmission, can be reproduced in different time scales and frequency ranges.
NUMERICAL SIMULATION OF PROPAGATION OF EM PULSE THROUGH LOSSLESS NON-UNIFORM DIELECTRIC SLAB USING CHARACTERISTIC-BASED METHOD
2008-01-19
PIER
Vol. 81, 183-195, 2008
download: 688
A New 2-18 GHz Quad-Ridged Horn Antenna
Ramin Dehdasht-Heydari Hamid Reza Hassani Ali Reza Mallahzadeh
A novel design of a dual-polarized broadband 2-18 GHz horn antenna with VSWR≤2.2 is presented. The designed horn antenna is most suitable as a feed element in reflectors of the radar systems and EMC applications. A coaxial line to quadruple-ridged waveguide transition with a new conical cavity back and a technique for tapering the flared section of the horn is introduced to improve the return loss and matching of the impedance, respectively. In order to overcome the deterioration of the broadside radiation pattern at higher frequencies, common to broad band ridged horn antennas, a new modified horn antenna with arc shaped aperture is introduced. Results of simulation obtained via two different software packages, HFSS and CST, for VSWR, isolation, radiation patterns, and gain of the designed quad ridged horn antenna as well as the modified horn antenna are presented and discussed.
A NEW 2-18 GHZ QUAD-RIDGED HORN ANTENNA
2008-01-17
PIER
Vol. 81, 167-182, 2008
download: 112
A Hybrid Multimode Contour Integral Method for Analysis of the h -Plane Waveguide Discontinuties
Ali Banai Ali Hashemi
A hybrid method is introduced for analysis of the H-plane waveguide discontinuities. It combines multimode contour integral and mode matching techniques. The process is based on dividing the circuit structure into key building blocks and finding the multimode scattering matrix of each block individually. The multimode scattering matrix of the whole structure can be found by cascading these blocks. Also contour integral method is developed for analysis of multi-media circuits. Therefore, it is possible to analyze H-plane waveguide filters with dielectric resonators using this method. The accuracy and run time of the purposed method is compared with those reported in literatures and/or Ansoft HFSS software.
A HYBRID MULTIMODE CONTOUR INTEGRAL METHOD FOR ANALYSIS OF THE H-PLANE WAVEGUIDE DISCONTINUTIES