Tarbiat Modares University
The Modares Journal of Electrical Engineering
2228527X
2476681X
2
1
2010
10
03
EFFECTS OF FACET PHASES AND REFLECTIVITY ON THE INTERNAL OPTICAL FIELD IN QWSDFB SEMICONDUCTOR LASERS
1
12
EN
Fateme
SHAHSHAHANI
Amirkabir university of technology
Az.zahra university,tehran
f_shahshahani@alzahra.ac.ir
Vahid
AHMADI
Tarbiat Modarres University
av1385@gmail.com
Kavous
MIRABBASZADEH
Amirkabir university of technology
In this paper, the effects of reflected waves of the facets on the internal optical intensity of semiconductor DFB lasers are investigated. The uniformity of optical intensity along the cavity length is evaluated with flatness parameter. The dependence of this parameter on coupling coefficient, reflectivity and grating phase at the facets is also studied. This investigation shows that in some structures reflected waves of the facets cause optical intensity along the cavity length to have more uniformed distribution than a DFB laser with antireflective facets. It is also shown that flatness parameter is very sensitive to grating phase .Thus it is necessary for designing a DFB laser to consider the effects of reflected wave and grating phase at both ends of cavity in order to increase the stability of the laser against SHB (Spatial Hole Burning) effect. The effects of reflectivity and grating phase on longitudinal distribution of photon and carrier density above threshold are investigated, too.
QWSDFB,Distributed feedback Lasers,Facet Reflectivity,Spatial HoleBurning
http://mjee.modares.ac.ir/article_2035.html
http://mjee.modares.ac.ir/article_2035_e2384389e25b8c6f219587f81acd8ef9.pdf
Tarbiat Modares University
The Modares Journal of Electrical Engineering
2228527X
2476681X
2
1
2010
10
03
APPLICATION OF THE METHOD OF LEAST SQUARES FOR THE ANALYSIS AND DESIGN OF THE ELECTROMAGENTIC ENGINEERING PROBLEMS
13
34
EN
HOMAYOUN
OREYZI
Iran University of Science and Technology
h_oraizi@iust.ac.ir
In this paper, some applications of the Method of Least Squares (MLS) for the solution of various problems in electromagnetics engineering is briefly reviewed. Here, MLS is employed for the solution of various problems such as solution of equations, curve fitting to measured data, generalized Fourier coefficients, linear operator equations, inegrodifferential equations, electrostatics and magnetostatics problems, boundary value problems (by the Least Square Boundary Residual Method LSBRM), design of impedance transformers and matching by step and tapered lines, optimum design of multihole directional couplers, coupledline couplers, branch line couplers, ring couplers, analysis of wire antennas, antenna pattern synthesis, array synthesis and scattering. In this study, it becomes clear that MLS can be applied to devise effective numerical algorithms for the analysis and design of problems in the subject areas of radiation, scattering, antennas, microwaves, engineering mathematic, etc. Some papers and books published in the area of MLS applications for the analysis and design of problems in electromagnetics engineering are grouped and presented in references.
Method of Least Squares,Least Squares Boundary Residual Method,Numerical Methods in Electromagnetics,Error Function,Optimization,Minimization,Solution of Equations,Linear Equations,IntegroDifferential Equations,Microwave Devices,Antennas,Arrays,Radiators,scattering
http://mjee.modares.ac.ir/article_2036.html
http://mjee.modares.ac.ir/article_2036_b5f1dea068caae7f4eefa0efd754dd8c.pdf
Tarbiat Modares University
The Modares Journal of Electrical Engineering
2228527X
2476681X
2
1
2010
10
03
DESIGN, OPTIMIZATION AND ANALYSIS OF HIGH POWER AMPLIFIER IN THE KA BAND
35
50
EN
Abdol Ali

ABDIPOUR
Amirkabir university of technology
Mohammad
Hakkak
Tarbiat Modarres University
Zahra
GHANIAN
Amirkabir university of technology
The graphical technique for nonlinear circuits was described that enable us to optimize circuits to obtain maximum output power, maximum efficiency or minimum intermodulation.
According to this method a high power amplifier in the Ka band was designed. Using a nonlinear model of the transistor, optimum slope for loadline was determined so that maximum power at the output was obtainable, then the output matching circuit was synthesized. Finally, the nonlinear network of the high power amplifier was analyzed by the harmonic balance method and the output load cycles were optimized by modification of the bias point or output matching network.
nonlinear model,PHEMT,graphical optimization,load cycle,Harmonic Balance,High Power Amplifier
http://mjee.modares.ac.ir/article_2037.html
http://mjee.modares.ac.ir/article_2037_5b717c44aceec1efb6beb5fe19e3dd25.pdf
Tarbiat Modares University
The Modares Journal of Electrical Engineering
2228527X
2476681X
2
1
2010
10
03
FIBER OPTIC NETWORKS PERFORMANCE EVALUATION
51
76
EN
MAJID

MALAKOUTI
Iran Telecommunication Research Center
majid_malakuti@yahoo.com
Nasrollah

GRANPAYEH
K.N.Toosi university
Performance of the fiber optic networks with different physical topologies such as pointtopoint, bus, ring and star, with respect to requirements as bit rates, topology structure, bit. error rate (BER) and optical component characteristics including optical amplifiers, filters, sources and detectors, are analyzed and simulated.
For this purpose, maximum number of supportable nodes and throughput, crosstalk due to optical amplifiers and optical filters, reliability, physical limitations and fiber induced limitations such as dispersion and nonlinear effects (self phase modulation) are considered as performance evaluation criteria of different topologies.
Dispersion and nonlinearities are simulated with splitstep Fourier method, sometimes referred to as beampropagation method. The fiber length can be estimated by this method, with respect to above effects and maximum tolerable power penalties. Parameters such as maximum number of supportable nodes and crosstalk are evaluated using amount of degradation in BER of receiver, BER is calculated using Gaussian approximation. Reliability of networks is modeled on the bypassing of the failed station as recovery mechanism in ring and bus networks and reliable assumption for central node in star network. By the way physical limitations in each topology, regarding its structure, are derived as an economical criterion.
Results indicate that no topology can be preferred to others, however imposed limitations and requirements determine the optimum topology. Neglecting economical aspects, star topology is preferred from different points of view such as reliability, crosstalk and maximum number of supportable nodes. Results of above simulations can be used in calculating power penalties of different factors such as dispersion, crosstalk and nonlinearities. This penalties perform important role in estimating power budget of networks.
Self Phase Modulation,Traveling Wave Amplifier,Erbium Doped Fiber Amplifier,Crosstalk,Extinction Ratio,FabryPerot Filter
http://mjee.modares.ac.ir/article_2038.html
http://mjee.modares.ac.ir/article_2038_d5959b426ccd9403d270badaef788ebf.pdf
Tarbiat Modares University
The Modares Journal of Electrical Engineering
2228527X
2476681X
2
1
2010
10
03
ANALYSIS OF LARGE ELECTROMAGNETIC PULSE SIMULATORS USING THE ELECTRIC FIELD INTEGRAL EQUATION METHOD IN TIME DOMAIN
77
94
EN
Jasem
JAMALI
Amirkabir university of technology
Ramin
AGHAJAFARI
Atomic Energy Organization of Iran
Ruzbeh
MOINI
Amirkabir university of technology
moini@cic.aut.ac.ir
Seyed hossin
SADEGHI
Amirkabir university of technology
A timedomain approach is presented to calculate electromagnetic fields inside a large Electromagnetic Pulse (EMP) simulator. This type of EMP simulator is used for studying the effect of electromagnetic pulses on electrical apparatus in various structures such as vehicles, a reoplanes, etc. The simulator consists of three planar transmission lines. To solve the problem, we first model the metallic structure of the simulator as a grid of conducting wires. The numerical solution of the governing electric field integral equation is then obtained using the method of moments in time domain. To demonstrate the accuracy of the model, we consider a typical EMP simulator. The comparison of our results with those obtained experimentally in the literature validates the model introduced in this paper.
Electromagnetic pulse,Simulator,integral equation,Method of Moment,time domain
http://mjee.modares.ac.ir/article_2039.html
http://mjee.modares.ac.ir/article_2039_229540818da895150353747d1a2f1ea5.pdf
Tarbiat Modares University
The Modares Journal of Electrical Engineering
2228527X
2476681X
2
1
2010
10
03
CORROSION OF CHROMATE CONVERSION COATINGS ON ALUMINUM ALLOYS IN ELECTRICAL AND ELECTRONIC EQUIPMENT
95
104
EN
Reza

SHOJA RAZAVI
Malek Ashtar University of Technology
shoja_r@yahoo.com
Taghi
SHAHRABI
Tarbiat Modares University
Reza
MOZAFARINIA
Malek Ashtar University of Technology
Chromate conversion coating is applied on aluminum 6061. The optimum conditions for chromate bath composition and immersion time are also obtained for standard requirements provision such as corrosion resistance in salt spray test, electrical resistance and coating quality. The applied coatings are electrochemically tested in sea and distilled water. According to Tafel and cyclic polarization curves, the protection mechanism are evaluated in said environments. This evaluation has shown the formation of passive film layer, contains chromate and alumina on the base. The proper behavior of corrosion and electrical conductivity is probably due to this mechanism.
Corrosion,Chromate coating,Aluminum and Electrical and electronic equipment
http://mjee.modares.ac.ir/article_2040.html
http://mjee.modares.ac.ir/article_2040_0922dfb6e83d1999c8327594b34f513a.pdf
Tarbiat Modares University
The Modares Journal of Electrical Engineering
2228527X
2476681X
2
1
2010
10
03
A NEW METHOD FOR TOOLPATH GENERATION AND ADAPTIVE INTERPOLATION OF A THREEAXIS CNC MILLING MACHINE
105
114
EN
Vahid
JOUHARI MAJD
Tarbiat Modarres University
majd@modares.ac.ir
Homan
HASANZADEGAN
Tarbiat Modarres University
In this paper we present a new method for toolpath generation and adaptive interpolation for a threeaxis CNC milling machine. This method satisfied the force and / or the error conditions by using a variabledirection variablefeedrate strategy based on Maximum Feedrate Map. The proposed adaptive interpolator modifies the cutting path and the moving direction according to the actual instantaneous position error in real time. It also adaptively slows down the speed of the cutting tool if the position error exceeds a permissible threshold so as to decrease the error. As the cutting points on the spline at each cycle are not calculated beforehand, memory requirement for the interpolator drastically reduces. The significance of the proposed method on the reduction of the cutting error in the presence of disturbance is demonstrated via computer simulations.
Maximum Feedrate Map,Path Planning,Adaptive Interpolation
http://mjee.modares.ac.ir/article_2041.html
http://mjee.modares.ac.ir/article_2041_97ae38c49bac08655a12af08ffd53682.pdf
Tarbiat Modares University
The Modares Journal of Electrical Engineering
2228527X
2476681X
2
1
2010
10
03
AN IMPROVED MODEL BASED ON UTD FOR MULTIPLE DIFFRACTIONS BY BUILDINGS
116
126
EN
Reza
ARABLOUEI
Amirkabir university of technology
a7923221@aut.ac.ir
Ayaz
GHORBANE
Amirkabir University of Technology
ghorbani@aut.ac.ir
In this paper, a new propagation model based on UTD for multiple diffraction paths in cellular mobile radio communications in urban environments is proposed. Moreover, the most rigorous novel UTDbased expressions for multiple diffractions by buildings and excess path losses are d  rived and analyzed. For this purpose, building rows are supposed to have rectangular crosssections with the same heights and spacings. In addition, in this analysis actual electrical
roperties of buildings are regarded.
Previous studies have been concentrated on the simplified models that approximated building rows as absorbing halfscreens or perfectly conducting half screens (knifeedges) or 90 degrees wedges. In this work, buildings are assumed flatroofed parallel rows of dielectric blocks and their actual relative permittivity and conductivity are applied.
Urban radio propagation,multiple building diffractions,excess path loss,uniform theory of diffraction,land mobile radio cellular systems
http://mjee.modares.ac.ir/article_2042.html
http://mjee.modares.ac.ir/article_2042_645058e54be62d0f5b909faa8a9161cb.pdf
Tarbiat Modares University
The Modares Journal of Electrical Engineering
2228527X
2476681X
2
1
2010
10
03
A NOVEL ACTIVE POWER FILTER CONTROL METHODOLOGY
127
138
EN
ALI
YAZDIAN VARJANI
TARBIAT MODARRES UNIVERSITY
yazdian@modares.ac.ir
Jo
CHICHARO
Wollongog university,Australia
Sarat

PERERA
Wollongog university,Australia
This paper presents a new control methodology for active power filters that provide an adaptive online harmonic estimation with partial and selective harmonic reduction schemes, which has been implemented within an integrated controller. The proposed approach is to provide partial and selective reduction of those individual harmonics which exceed the recommended levels as set by regulatory bodies reduces the rating of active power filters thus leading to cost savings. This approach contrasts with existing techniques in which the objective is to reduce all possible harmonic components to zero. Performance evaluation of the proposed technique for harmonic estimation for timevarying nonlinear load is carried out when the simulation and experimental results show that the proposed control strategy provides a new alternative for harmonic reduction in power system.
Harmonic estimation,Active power filter,Harmonic Reduction
http://mjee.modares.ac.ir/article_2043.html
http://mjee.modares.ac.ir/article_2043_9d6d3de282774456072fd45c692128a1.pdf