PIER | PIER Journals

2007-12-23

PIER

Vol. 80, 477-497, 2008

download: 141

The m -DSO-ESPRIT Method for Maximum Likelihood DOA Estimation

Leonardo Lizzi Federico Viani Manuel Benedetti Paolo Rocca Andrea Massa

The estimation of the directions-of-arrival (DoAs) of multiple signals is a topic of great relevance in smart antenna synthesis and signal processing applications. In this paper, a memory-based method is proposed to compute the maximum likelihood (ML) DoA estimates. Such a conceptually-simple technique is based on the datasupported optimization (DSO) and the estimation of signal parameters via rotational invariance technique (ESPRIT), but fully exploits a memory mechanism for improving the estimation accuracy especially when dealing with critical scenarios characterized by low signal-tonoise ratios (SNR) or/and small number of snapshots. Simulation results assess the potentialities and limitations of the proposed approach that favorably compares with state-of-the-art methods.

THE M-DSO-ESPRIT METHOD FOR MAXIMUM LIKELIHOOD DOA ESTIMATION

2007-12-23

PIER

Vol. 80, 461-476, 2008

doi:10.2528/PIER07121503

download: 164

Improved GA and PSO Culled Hybrid Algorithm for Antenna Array Pattern Synthesis

Wen-Tao Li Xiao-Wei Shi Le Xu Yong-Qiang Hei

In this paper, a new evolutionary learning algorithm based on a hybrid of improved real-code genetic algorithm (IGA) and particle swarm optimization (PSO) called HIGAPSO is proposed. In order to overcome the drawbacks of standard genetic algorithm and particle swarm optimization, some improved mechanisms based on non-linear ranking selection, competition and selection among several crossover offspring and adaptive change of mutation scaling are adopted in the genetic algorithm, and dynamical parameters are adopted in PSO. The new population is produced through three approaches to improve the global optimization performance, which are elitist strategy, PSO strategy and improved genetic algorithm (IGA) strategy. The effectiveness of the proposed algorithm has been compared with GAs and PSO, synthesizing a circular array, a linear array and a base station array. Results show that the proposed algorithm is able to adapt itself to different electromagnetic optimization problems more effectively.

IMPROVED GA AND PSO CULLED HYBRID ALGORITHM FOR ANTENNA ARRAY PATTERN SYNTHESIS

2007-12-23

PIER

Vol. 80, 447-460, 2008

doi:10.2528/PIER07121409

download: 227

Application of Synthetic Bandwidth Approach in SAR Polar Format Algorithm Using the Deramp Technique

Xin Nie Dai-Yin Zhu Zhao-Da Zhu

The problem of wide bandwidth management in ultra-high resolution SAR systems can be solved by adopting stepped chirps and applying synthetic bandwidth approach. However, high resolution SAR image formation is a non-separable 2-D impulse compression processing, so the synthetic bandwidth procedure should be modified correspondingly with the image formation algorithm adopted. This paper demonstrates the application of synthetic bandwidth approach in SAR Polar Format Algorithm (PFA) using the deramp technique. The problem of motion compensation between the sub-pulses within a burst is discussed, and the signalpro cessing flows are investigated in detail. The presented approach is validated by point target simulation.

APPLICATION OF SYNTHETIC BANDWIDTH APPROACH IN SAR POLAR FORMAT ALGORITHM USING THE DERAMP TECHNIQUE

2007-12-22

PIER

Vol. 80, 431-445, 2008

doi:10.2528/PIER07120502

download: 188

Photonic Crystals as Infrared Broadband Reflectors with Different Angles of Incidence: a Comparative Study

Narendra Kumar Sant Ojha

In this communication, we theoretically report the reflection properties of a photonic crystal with alternate layers of air and GaAs for specified values of the lattice parameters. By employing the transfer matrix approach, the reflection spectra of the layered media are obtained for chosen sets of number of unit cells and incident angles. It is observed that the photonic crystals with different number of unit cells completely reflect a wide band in the infrared region of radiation. Also, we find that the reflectivity decreases and the completely reflected bands are shifted towards lower wavelength side with increase in the incident angle. Further, the reflected broadbands in the reflection spectra correspond to the forbidden ranges of wavelength obtained by using the analogy of Kronig-Penney model. It indicates that the completely reflected ranges are forbidden bandgaps, which is considered as an important feature of the proposed photonic crystals.

PHOTONIC CRYSTALS AS INFRARED BROADBAND REFLECTORS WITH DIFFERENT ANGLES OF INCIDENCE: A COMPARATIVE STUDY

2007-12-20

PIER

Vol. 80, 421-430, 2008

doi:10.2528/PIER07121002

download: 112

Photonic Crystal Narrow Filters with Negative Refractive Index Structural Defects

Zhuo-Yuan Wang Xiao-Ming Cheng Xiao-Qi He Sheng-Li Fan Wen-Zhe Yan

This paper presents a proposal of taking the left-handed material as the structural defects of one-dimensional photonic crystals and uses the transfer matrix method to analyze the band-gap of that structure. The simulation result shows that the structure investigated can be considered as a narrow pass band optical filter. By tuning the refractive index of the left-handed material, the ideal transmission rate in the pass band is as higher as 99.99%, while in the band-gap is lower than 0.01%. In addition, we show that the bandwidth can be increased by reducing the cycle number of the photonic crystals.

PHOTONIC CRYSTAL NARROW FILTERS WITH NEGATIVE REFRACTIVE INDEX STRUCTURAL DEFECTS

2007-12-18

PIER

Vol. 80, 409-420, 2008

doi:10.2528/PIER07120302

download: 110

Towards the Dispersion Relations for Dielectric Optical Fibers with Helical Windings Under Slow- and Fast-Wave Considerations - a Comparative Analysis

Deepak Kumar Pankaj Choudhury Onkar Singh II

The paper presents the electromagnetic (EM) wave propagation in cylindrical optical fibers with helical windings under slow- and fast-wave considerations. Field components are deduced for both the cases, and also, the dispersion relations are obtained by applying the boundary conditions, as modified by the presence of conducting helical windings. Two special cases are considered corresponding to the values of the helical pitch angle as 0^◦ and 90^◦. A comparison of the dispersion relations is presented.

TOWARDS THE DISPERSION RELATIONS FOR DIELECTRIC OPTICAL FIBERS WITH HELICAL WINDINGS UNDER SLOW- AND FAST-WAVE CONSIDERATIONS - A COMPARATIVE ANALYSIS

2007-12-18

PIER

Vol. 80, 393-408, 2008

doi:10.2528/PIER07120703

download: 149

A Novel FDTD Approach Featuring Two-Level Parallelization on PC Cluster

Yu Liu Zheng Liang Ziqiang Yang

To improve the parallel efficiency in the case of the finegrained FDTD computing on PC cluster, the concept of "two level parallelization on PC cluster" is presented, and a high performance MPI-OpenMP hybrid FDTD algorithmis developed. In the hybrid algorithm, MPI is used in conjunction with OpenMP multithreading to achieve two level parallelismof the data and tasks at the basis of the domain decomposition FDTD method. Besides, to enhance the flexibility of the parallel FDTD, the interpolation between subspaces is also discussed. The simulation example of a printed antenna for automobile is given. Computations are performed for different numbers of PCs and contrasted with two conventional parallel FDTD algorithms on PC cluster. The results show that with the decrease of the computational granularity on each computer, the novel algorithm is more efficient, and moreover, it can also lessen the influence of the sub-domains virtual topology on the parallel FDTD performance.

A NOVEL FDTD APPROACH FEATURING TWO-LEVEL PARALLELIZATION ON PC CLUSTER

2007-12-17

PIER

Vol. 80, 381-392, 2008

doi:10.2528/PIER07120902

download: 155

Numerical Modeling of Active Devices Characterized by Measured s -Parameters in FDTD

Dao Yi Su De-Min Fu Zhi-Hui Chen

A new FDTD modeling approach for active devices characterized by measured S-parameters is presented. This approach applies vector fitting technique and piecewise linear recursive convolution (PLRC) technique to complete modeling process, and does not need to know the equivalent circuits of active devices. It preserves the explicit nature of the traditional FDTD method, and a general updated formula is derived. Furthermore, the main data-processing procedure is directly handled over the frequency band of interest, which avoids the time-domain non-causal error in traditional techniques.

NUMERICAL MODELING OF ACTIVE DEVICES CHARACTERIZED BY MEASURED S-PARAMETERS IN FDTD

2007-12-17

PIER

Vol. 80, 369-380, 2008

doi:10.2528/PIER07120303

download: 133

The Synthesis of Complex-Angle Zeros for on-Board Antenna Arrays

Gloria Gajardo-Silva Luis Landesa

Shelkunoff circle synthesis techniques are only effective for equispaced antenna arrays. These techniques are based on reorganizing the zeros on the Shelkunoff circle. We propose a technique based on locating complex-direction zeros to synthesize arbitrary on-board antenna arrays. It is based on the analytical continuation of Green's functions and on a new representation of the complex plane (analogous to the Shelkunoff circle).

THE SYNTHESIS OF COMPLEX-ANGLE ZEROS FOR ON-BOARD ANTENNA ARRAYS

2007-12-17

PIER

Vol. 80, 349-368, 2008

doi:10.2528/PIER07111503

download: 147

Mutual External Inductance in Stripline Structures

Marina Koledintseva James Drewniak Thomas Van Doren David Pommerenke Matteo Cocchini David Hockanson

The Method of Edge Currents (MEC) proposed in our previous paper [1] is applied herein for calculating the mutual external inductance associated with fringing magnetic fields that wrap ground planes of a stripline structure. This method employs a quasi-static approach, image theory, and direct magnetic field integration. The resultant mutual external inductance is frequency-independent. The approach has been applied to estimating mutual inductance for both symmetrical and asymmetrical stripline structures. Offset of the signal trace from the centered position both in horizontal and vertical directions is taken into account in asymmetrical structures. The results are compared with numerical simulations using the CST Microwave Studio Software.

MUTUAL EXTERNAL INDUCTANCE IN STRIPLINE STRUCTURES

2007-12-12

PIER

Vol. 80, 337-348, 2008

doi:10.2528/PIER07120202

download: 251

Frequency and Time Domain Characteristic of a Novel Notch Frequency UWB Antenna

Lida Akhoondzadeh-Asl Masum Fardis Ali Abolghasemi Gholamreza R. Dadashzadeh

An ultra-wideband (UWB) monopole antenna with a band-notch characteristic is presented which needs only two parameters to tune the notch frequency. The proposed monopole antenna is embedded with a crescent slot, whose length is determined by parametric study. By adjusting the slot length, the notched frequency band within the antenna's operating bandwidth can be easily controlled. Also, the time-domain behaviours are discussed and the fidelity factor is calculated.

FREQUENCY AND TIME DOMAIN CHARACTERISTIC OF A NOVEL NOTCH FREQUENCY UWB ANTENNA

2007-12-12

PIER

Vol. 80, 321-336, 2008

doi:10.2528/PIER07112804

download: 143

Prediction of the SAR Level Induced in a Dielectric Sphere by a Thin Wire Dipole Antenna

Nikolaos Kouveliotis Christos N. Capsalis

The interaction between a dipole antenna,represen ting a simplified model of a mobile terminal,and a homogeneous spherical model of the human head is examined. The Finite Difference Time Domain (FDTD) method is utilized,to calculate the either peak or average value of the Specific Absorption Rate (SAR),corresp onding to different distances between antenna and phantom. The variation of the SAR with the distance between the mobile antenna and the human phantom has gained significant attention in the recent literature and is investigated here. An attempt to correlate the computed SAR values with the basic antenna characteristics,suc h as the standing wave ratio (SWR),rev eals that a precise estimation of the level of the SAR can be achieved regarding data acquired from the mobile terminal.

PREDICTION OF THE SAR LEVEL INDUCED IN A DIELECTRIC SPHERE BY A THIN WIRE DIPOLE ANTENNA

2007-12-05

PIER

Vol. 80, 307-320, 2008

doi:10.2528/PIER07112202

download: 239

Microwave/Millimeter-Wave Generation Using Multi-Wavelength Photonic Crystal Fiber Brillouin Laser

Guo-Feng Shen Xian-Min Zhang Hao Chi Xiao-Feng Jin

An all-optical microwave generation using a multiwavelength photonic crystal fiber Brillouin laser is presented. A highly nonlinear photonic crystal fiber with the length of 25m is used as Brillouin gain medium. A Fabry-Perot cavity with two fiber Bragg gratings as reflectors are designed in order to enhance the Brillouin conversion efficiency. The fiber Bragg gratings can be used to selectively excite the jth-order Stokes' wave and suppress other order Stokes' waves. The mechanism for microwave/millimeterwave generation is theoretically analyzed. In the experiment, both 9.788 GHz and 19.579 GHz microwave signals are achieved through mixing the pump wave with the first-order and the second-order Stokes' waves.

MICROWAVE/MILLIMETER-WAVE GENERATION USING MULTI-WAVELENGTH PHOTONIC CRYSTAL FIBER BRILLOUIN LASER

2007-12-04

PIER

Vol. 80, 295-306, 2008

doi:10.2528/PIER07112706

download: 138

Empirical Characterization of Wood Surfaces by Means of Iterative Autocorrelation of Laser Speckle Patterns.

Juan-Antonio Martinez-Rojas Jesus Alpuente-Hermosilla Estefania Bolivar Pablo-Luis Lopez-Espi Santiago Vignote Martinez Rojas

A simple and inexpensive method for the qualitative characterization of wood surfaces is presented. It is based on the iterative autocorrelation of laser speckle patterns produced by diffuse laser illumination of the wood surfaces.The method exploits the high spatial frequency content of speckle images. A similar approach with raw conventional photographs taken with ordinary light would be very difficult. A few iterations of the algorithm are necessary, typically three or four, in order to visualize the most important periodic features of the surface. The processed patterns help in the study of surface parameters, to design new scattering models and to classify the wood species.

EMPIRICAL CHARACTERIZATION OF WOOD SURFACES BY MEANS OF ITERATIVE AUTOCORRELATION OF LASER SPECKLE PATTERNS.

2007-12-02

PIER

Vol. 80, 277-293, 2008

doi:10.2528/PIER07112505

download: 261

Study on Scintillation Considering Inner- and Outer-Scales for Laser Beam Propagation on the Slant Path through the Atmospheric Turbulence

Zhen-Sen Wu Hong-Yan Wei Rui-Ke Yang Li-Xin Guo

Based on both the modified Rytov method and the altitude-dependent model of the ITU-R slant atmospheric turbulence structure constant, the uniform model of scintillation index considering inner- and outer-scales is derived form weak to strong fluctuation regions with Gaussian beam propagation on the slant path, and can be degenerated to the result of the horizontal path with atmospheric structure constant is a fixed value. The numerical conclusions indicate the smaller wavelength, the inner-scale has a stronger impact on scintillation than outer-scale. But, in strong fluctuation, the outerscale effect is prominence. Finally, the numerical results are compared and verified with the experimental data.

STUDY ON SCINTILLATION CONSIDERING INNER- AND OUTER-SCALES FOR LASER BEAM PROPAGATION ON THE SLANT PATH THROUGH THE ATMOSPHERIC TURBULENCE

2007-12-02

PIER

Vol. 80, 253-275, 2008

doi:10.2528/PIER07111003

download: 115

A Novel Design Methodology of Multi-Clad Single Mode Optical Fiber for Broadband Optical Networks

H. Shahoei Hassan Ghafoori-Fard Ali Rostami

In this paper two multi-clad RI- and RII-type optical fiber structures for small dispersion and dispersion slope as well as large bandwidth are considered and novel design strategy for this purpose is presented. The suggested design method uses the Differential Evolution (DE) approach. We put absolute value of dispersion factor as fitness function in differential evolution method. This algorithm successfully introduces a special fiber including so small dispersion and dispersion slope in the predefined wavelength duration. Also, the proposed method can set zero dispersion wavelengths with high accuracy compared other traditional methods. The designed dispersion-shifted RI single-mode fiber has the bandwidth of 600nm and the max amount of 1.36 (ps/km/nm) in that duration which is an ideal result.

A NOVEL DESIGN METHODOLOGY OF MULTI-CLAD SINGLE MODE OPTICAL FIBER FOR BROADBAND OPTICAL NETWORKS

2007-11-29

PIER

Vol. 80, 241-252, 2008

doi:10.2528/PIER07111701

download: 227

Nonlinear Stability Analysis of an Oscillator with Distributed Element Resonator

Hamid Vahdati Abdolali Abdipour

In this paper a complete analysis to the stability of a microwave oscillator with distributed element resonator is presented. In this type of oscillators, the circuit description changes form ordinary differential equations to partial deferential equations. In this paper a Gunn diode oscillator with distributed elements resonator is analyzed. The instability condition of the startup phase and the stability condition of the steady state oscillation is investigated.

NONLINEAR STABILITY ANALYSIS OF AN OSCILLATOR WITH DISTRIBUTED ELEMENT RESONATOR

2007-11-28

PIER

Vol. 80, 225-239, 2008

doi:10.2528/PIER07102101

download: 202

Combing Multilevel Green's Function Interpolation Method with Volume Loop Bases for Inductance Extraction Problems

Hao-Gang Wang Zhao Peng

In this paper,a fast integral equation method is developed for extracting the inductances in RF ICs,RF MEMs,IC packages,and deep submicron ICs etc. This method combines a recently developed Multilevel Green's Function Interpolation Method (MLGFIM) [1,2] with the volume integral equation discretized using Volume Loop (VL) basis functions. In it,instead of using the filaments model to simulate the currents flowing in the inductors,w e use the conventional SWG basis functions for this kind of basis functions is flexible for problems with complex geometries. The shortest path finding algorithm is also used to find the source loop basis functions. The inductance extractions from the straight line,the spiral inductors,the bump,and the parallel buses in this paper demonstrate the validity and efficiency of this hybrid method.

COMBING MULTILEVEL GREEN'S FUNCTION INTERPOLATION METHOD WITH VOLUME LOOP BASES FOR INDUCTANCE EXTRACTION PROBLEMS

2007-11-28

PIER

Vol. 80, 197-224, 2008

doi:10.2528/PIER07101504

download: 110

Method of Edge Currents for Calculating Mutual External Inductance in a Microstrip Structure

Marina Koledintseva James Drewniak Thomas Van Doren David Pommerenke Matteo Cocchini David Hockanson

Mutual external inductance (MEI) associated with fringing magnetic fields in planar transmission lines is a cause of socalled "ground plane noise", which leads to radiation from printed circuit boards in high-speed electronic equipment. Herein, a Method of Edge Currents (MEC) is proposed for calculating the MEI associated with fringing magnetic fields that wrap the ground plane of a microstrip line. This method employs a quasi-magnetostatic approach and direct magnetic field integration, so the resultant MEI is frequencyindependent. It is shown that when infinitely wide ground planes are cut to form ground planes of finite width, the residual surface currents on the tails that are cut off may be redistributed on the edges of the ground planes of finite thickness, forming edge currents. These edge currents shrink to filament currents when the thickness of the ground plane becomes negligible. It is shown that the mutual external inductance is determined by the magnetic flux produced by these edge currents, while the contributions to the magnetic flux by the currents from the signal trace and the finite-size ground plane completely compensate each other. This approach has been applied to estimating the mutual inductance for symmetrical and asymmetrical microstrip lines.

METHOD OF EDGE CURRENTS FOR CALCULATING MUTUAL EXTERNAL INDUCTANCE IN A MICROSTRIP STRUCTURE

2007-11-28

PIER

Vol. 80, 179-196, 2008

doi:10.2528/PIER07111504

download: 150

Enhancement of Directivity Using 2D-Electromagnetic Crystals Near the Band-Gap Edge: a Full-Wave Approach

Lara Pajewski Lorenzo Rinaldi Giuseppe Schettini

A deep analysis of the directivity enhancement, due to the insertion of a simple linear antenna into a dielectric EBG, is presented. The operative frequency is chosen near a band-gap edge. The planewave expansion method is used in order to obtain the Bloch dispersion diagrams of infinite two-dimensional EBGs. A rigorous cylindricalwave approach is used to analyze two-dimensional EBGs with finite size, excited by a line source. We apply these tools to the analysis of different emitting devices, and propose solutions to improve their performances.