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Total 22 records

    Output voltage quality intensification of diode clamped multilevel inverters using FM PWM technique

    , Article 2012 3rd Power Electronics and Drive Systems Technology, PEDSTC 2012, 15 February 2012 through 16 February 2012 ; February , 2012 , Pages 98-102 ; 9781467301114 (ISBN) Najmi, V ; Ebrahimi, S ; Oraee, H ; Sharif University of Technology
    2012
    Abstract
    Improvement in switching techniques is one of the effective methods for increasing the voltage quality in Multilevel Inverters. In this paper, a novel switching technique using frequency modulation is proposed to achieve high quality output voltage of multilevel inverters. This method is employed to different configurations of multilevel inverters consist of Diode Clamped (or Neutral Point Clamped), Flying Capacitor and Cascaded H-bridge. Each multilevel inverter which utilizes this technique is modeled and simulated to investigate the performance of this method by the help of MATLAB/Simulink software. The Results show that this innovative method considerably reduces total harmonic... 

    A new definition for total harmonic distortion in inverter-fed induction motors including loss considerations

    , Article 42nd International Conference on Large High Voltage Electric Systems 2008, CIGRE 2008, Paris, 24 August 2008 through 29 August 2008 ; 2008 Fard, H. G ; Kaboli, S ; Oraee, H ; Sharif University of Technology
    2008
    Abstract
    Harmonic information is necessary tools in the estimation of motors life and performance. The conventional expression of harmonic amount is carried out by total Harmonic distortion. This distortion factor is only related to amplitude of harmonics while the motor loss is affected by frequency domain of them. In this paper a new definition of this factor has been presented. This definition includes the frequency of harmonics as well as their amplitudes. Experimental results verify the validity of this new definition  

    Speckle noise reduction of ultrasound images using M-band wavelet transform and wiener filter in a homomorphic framework

    , Article 1st International Conference on BioMedical Engineering and Informatics, BMEI 2008, Sanya, Hainan, 27 May 2008 through 30 May 2008 ; Volume 2 , 2008 , Pages 510-515 ; 9780769531182 (ISBN) Vosoughi, A ; Shamsollahi, M. B ; Sharif University of Technology
    2008
    Abstract
    In this paper we make use of M-band discrete wavelet transform (MDWT) and Wiener filter for speckle noise suppression of ultrasound images. Assuming multiplicative model for speckle noise, by applying logarithmic transform to noisy observation we convert multiplicative noise to additive one. Then, speckle noise can be reduced by taking the M-band wavelet transform of log-transformed observation and employing an adaptive thresholding technique. In order to improve the performance of this denosing approach, we propose a preprocessing stage which exploits Wiener filtering. Through this stage logtransformed observation is separated into two images and then each of these two images is denoised... 

    A low-power complex active-RC filter for low-IF receivers using a new class-AB operational amplifier

    , Article 2007 International Symposium on Integrated Circuits, ISIC, Singapore, 26 September 2007 through 28 September 2007 ; 2007 , Pages 309-312 ; 1424407974 (ISBN); 9781424407972 (ISBN) Abrishamifar, A ; Zanbaghi, R ; Mehrmanesh, S ; Lahiji, G. R ; Sharif University of Technology
    2007
    Abstract
    The design of a complex active-RC filter for low-IF Wireless applications is described. Fifth-order complex Butterworth filter is designed using Class-AB operational amplifier architecture. This new structure makes the filter suitable for low power applications with high dynamic range. Simulation results show that the filter provides more than 40 dB image rejection ratio (IIR) and dynamic range of 82dB. The complete filter including on-chip tuning circuit consumes only 4.3mW with 1.8V single supply voltage. © 2007 IEEE  

    An efficient multi-band spectral subtraction method for robust speech recognition

    , Article 2007 9th International Symposium on Signal Processing and its Applications, ISSPA 2007, Sharjah, 12 February 2007 through 15 February 2007 ; 2007 ; 1424407796 (ISBN); 9781424407798 (ISBN) Safayani, M ; Sameti, H ; Babaali, B ; Manzuri Shalmani, M. T ; Sharif University of Technology
    2007
    Abstract
    In this paper we present a novel approach for adjusting a multi band spectral subtraction filter coefficients based on speech recognition system results. Currently most speech enhancement techniques are designed according to various waveform level criteria such as maximizing SNR or minimizing signal error. However improvement in these criteria does not necessarily result in increasing speech recognition performance. Only if these methods generate sequence of features that maximize or increase the likelihood of the correct transcription relative to other incorrect competing hypotheses, speech recognition performance will increase. Here we use an utterance with a known transcription and... 

    A novel control technique for Power Factor Correction in SEPIC converter utilizing input/output voltage waveforms sampling

    , Article PECon 2012 - 2012 IEEE International Conference on Power and Energy ; 2012 , Pages 268-273 ; 9781467350198 (ISBN) Keipour, A ; Sudi, Z ; Mohagheghi, E ; Lakmehsari, A. H ; Hajihosseinlu, A ; Sharif University of Technology
    2012
    Abstract
    In this study, a simple and novel control technique for Power Factor Correction (PFC) is introduced, which is a SEPIC-based (Single-ended Primary-inductor Converter based) rectifier with high input power factor. Operation of the proposed method is based on sampling of input and output voltages in SEPIC rectifier. Using samples of input and output voltage, this control system makes the input current to follow a sinusoidal path. As a result, the line current?'s Total Harmonic Distortion (THD) is reduced and the input power factor is improved. This paper also compares the new method with the conventional control method for the power factor correction. In order to examine the proposed control... 

    A novel control strategy for power factor corrections based on predictive algorithm

    , Article PEDSTC 2010 - 1st Power Electronics and Drive Systems and Technologies Conference, 17 February 2010 through 18 February 2010, Tehran ; 2010 , Pages 117-121 ; 9781424459728 (ISBN) Yazdanian, M ; Farhangi, S ; Zolghadri, M. R ; Sharif University of Technology
    2010
    Abstract
    A novel control strategy based on predictive control is presented for continuous conduction mode boost converter which operates as a power factor correction. In the proposed algorithm two horizons for the behavior of the circuit are predicted which improves the total harmonic distortion, mainly the low frequency harmonics. The algorithm doesn't need elaborating calculations therefore, implementation of the controller using low price processor is feasible. Moreover, an extra horizon of the prediction leads to expansion of the calculation time. Reduction of the harmonic distortion of the input current and improvement of the power factor have been demonstrated on an isolated boost PFC converter... 

    Analysis and design of 4-path filter using gyrator based complex impedance

    , Article AEU - International Journal of Electronics and Communications ; Volume 70, Issue 11 , 2016 , Pages 1532-1542 ; 14348411 (ISSN) Karami, P ; Behmanesh, B ; Atarodi, S. M ; Sharif University of Technology
    Elsevier GmbH 
    Abstract
    A novel N-path filter using a complex impedance is designed to replace the frontend SAW filters in receivers with on-chip bandpass filters. It is demonstrated that the center frequency of the filter can be tuned solely by changing the value of some capacitances without the need to change the clock frequency. In addition, thanks to the use of smaller capacitors, the silicon area is reduced compared to similar designs. The high-Q bandpass filter is realized utilizing two gyrators and an arrangement of four baseband capacitors with NMOS switches, driven by 4-phase 25% duty cycle clock signals. This paper also analyzes the performance of the proposed filter against imperfections such as thermal... 

    Reducing output voltage THD of a three-phase inverter with non-linear load using disturbance observer

    , Article 8th Power Electronics, Drive Systems and Technologies Conference, PEDSTC 2017, 14 February 2017 through 16 February 2017 ; 2017 , Pages 431-436 ; 9781509057665 (ISBN) Valizade Alavi, S ; Tahami, F ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2017
    Abstract
    Non-linear loads such as rectifiers are growing in industry. Three phase inverter with non-linear load can lead to highly distorted output voltage. This paper proposes a method for reducing voltage THD in three phase inverters with non-linear load. The proposed method considers the load current as a disturbance and provide a control strategy to reject it using the disturbance observer method. This method doesn't need any additional sensors or hardware and is implemented digitally in controller. Simulation results show that the presented method will reduce the total harmonic distortion of the output voltage. © 2017 IEEE  

    Half-band FIR fractional delay filters with closed-form coefficient formulas and modular implementation based on Lagrange interpolators

    , Article Signal Processing ; Volume 88, Issue 12 , 2008 , Pages 2913-2916 ; 01651684 (ISSN) Jahani Yekta, M. M ; Sharif University of Technology
    2008
    Abstract
    The Taylor series-based representation of the maximally flat (MF) FIR fractional delay (FD) filter is manipulated to obtain a FD filter with a wider band-width. The band-width of the proposed filter can approach π / 2 rads / s, which is 1.5 times that of the prototype one. The design has closed-form coefficient formulas as well as a modular implementation. These two properties make it a practically favourable one. © 2008 Elsevier B.V. All rights reserved  

    Transmitter leakage cancellation technique for CMOS SAW-less radio front-ends

    , Article Analog Integrated Circuits and Signal Processing ; Volume 93, Issue 3 , 2017 , Pages 383-394 ; 09251030 (ISSN) Shokrekhodaei, M ; Safarian, A ; Atarodi, M ; Sharif University of Technology
    Abstract
    A novel method of transmitter (TX) leakage cancellation is presented to improve the dynamic range of the receiver for wideband code division multiple access applications. The large TX leakage is attenuated within the low noise amplifier (LNA) output using a feed-forward path without any LNA noise figure degradation. A prototype has been designed and laid out in 0.18 μm CMOS technology. It achieves a maximum TX rejection of 18.5 dB with only 5.2 mA current consumption from 1.8 V supply voltage. LNA P-1dBCP (1 dB gain compression point) against TX leakage improves by more than 10 dB. Post layout simulations verify these results. Proposed structure dispels the requirement of off-chip surface... 

    Effect of out-of-band blockers on the required linearity, phase noise, and harmonic rejection of sdr receivers without input saw filter

    , Article IEEE Transactions on Microwave Theory and Techniques ; Volume 66, Issue 11 , 2018 , Pages 4913-4926 ; 00189480 (ISSN) Rasekh, A ; Bakhtiar, M. S ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2018
    Abstract
    The required linearity of wideband receivers for applications, such as software-defined radio in the absence of input surface-acoustic wave (SAW) filters, is studied. It is shown that the required linearity of wideband SAW-less receivers is surprisingly higher than what has been commonly assumed. For these receivers, although the out-of-band blockers can reduce the compression point of the receiver, they can also potentially generate interferers that appear in the desired frequency band, resulting in higher noise floor and signal corruption. The required out-of-band IIP2 and IIP3 of low-noise amplifier (LNA) and mixer for single and concurrent applications are analytically derived. The... 

    NF analysis of LNA with Lossy passive network at the input

    , Article 41st International Conference on Telecommunications and Signal Processing, TSP 2018, 4 July 2018 through 6 July 2018 ; 2018 ; 9781538646953 (ISBN) Rasekh, A ; Rabbani, R ; Sharif Bakhtiar, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2018
    Abstract
    It is widely accepted that the presence of a lossy network, such as a SAW filter or balun, at the input of LNA increases NF of the overall circuit by an amount equal to the insertion loss of the lossy network. In this work it is shown that this idea is not exactly true and it considerably underestimates the overall NF. To verify this claim, Z-model of the lossy network is added before the LNA and the overall noise figure is recalculated for some commonly used LNA topologies. It is shown that in common gate LNA and common source LNA with resistive feedback the accepted equation underestimates the overall NF by 1.3 dB for an insertion loss of 2 dB. In common source with resistive matching and... 

    Challenges of finite element analysis of re-solvers

    , Article IEEE Transactions on Energy Conversion ; 2018 ; 08858969 (ISSN) Saneie, H ; Alipour Sarabi, R ; Nasiri Gheidari, Z ; Tootoonchian, F ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2018
    Abstract
    Nowadays position sensors are increasingly used in many applications. One of the most commonly used sensors are resolvers. There are different types of resolvers including Wound Rotor (WR) resolvers, Variable Air-gap Length Variable Reluctance (VAGL-VR) resolvers, and Sinusoidal Rotor Variable Reluctance (SR-VR) resolvers. Regardless of the resolvers’ configurations, including linear, cylindrical and disk type, finite element analysis (FEA) is inseparable part of design and performance evaluation of these magnetic sensors. The scope of this study is to discuss challenges in the FEA of resolvers. The influence of mesh quality, time steps, stop time, excitation methods including volt-age... 

    Wide-Band RF front end for saw-less receivers employing active feedback and far out-of-band blocker rejection circuit

    , Article IEEE Journal of Solid-State Circuits ; Volume 54, Issue 6 , 2019 , Pages 1528-1540 ; 00189200 (ISSN) Rasekh, A ; Sharif Bakhtiar, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2019
    Abstract
    Elimination of the surface acoustic wave (SAW) filter from the input of a receiver can render it extremely vulnerable to various blockers and interferers. The presence of large out-of-band (OOB) blockers will result in the required linearity of the SAW-less receiver to be considerably higher than that of the conventional receivers with the input SAW filter. The ever-present undesirable signals that arise in the absence of the input SAW filter can be divided into two classes of far and near OOB blockers and interferers. Removal of these harmful signals requires two distinct approaches according to their nature. Two different methods for blocker and interferer rejection are introduced in this... 

    Challenges of Finite Element Analysis of Resolvers

    , Article IEEE Transactions on Energy Conversion ; Volume 34, Issue 2 , 2019 , Pages 973-983 ; 08858969 (ISSN) Saneie, H ; Alipour Sarabi, R ; Nasiri Gheidari, Z ; Tootoonchian, F ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2019
    Abstract
    Nowadays, position sensors are increasingly used in many applications. One of the most commonly used sensors are resolvers. There are different types of resolvers including wound rotor resolvers, variable air-gap length variable reluctance resolvers, and sinusoidal rotor variable reluctance resolvers. Regardless of the resolvers' configurations, including linear, cylindrical and disk type, finite element analysis (FEA) is inseparable part of design and the performance evaluation of these magnetic sensors. The scope of this study is to discuss challenges in the FEA of resolvers. The influence of mesh quality, time steps, stop time, excitation methods including voltage source and current... 

    Improved winding proposal for wound rotor resolver using genetic algorithm and winding function approach

    , Article IEEE Transactions on Industrial Electronics ; Volume 66, Issue 2 , 2019 , Pages 1325-1334 ; 02780046 (ISSN) Alipour Sarabi, R ; Nasiri Gheidari, Z ; Tootoonchian, F ; Oraee, H ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2019
    Abstract
    Among position sensors, resolvers are superior from reliability point of view. However, obtaining lower output voltage harmonics and simple manufacturing process is a challenge in the design and optimization of resolvers. In this paper, a metaheuristic optimization algorithm is used to minimize total harmonic distortion of the output signals, and consequently the estimated position error in concentrated coil wound field resolvers. Meanwhile, to minimize total coil numbers, manufacturing costs, and complexity of the winding process, modified objective function and constraints are proposed. In this way, a modified winding function method is employed for performance analysis of the axial flux... 

    A compact mixer and DAC for implementation of a direct conversion OQPSK transmitter

    , Article 2007 IEEE Region 10 Conference, TENCON 2007, Taipei, 30 October 2007 through 2 November 2007 ; 2007 ; 1424412722 (ISBN); 9781424412723 (ISBN) Chahardori, M ; Mehrmanesh, S ; Zamanlooy, B ; Atarodi, M ; Sharif University of Technology
    2007
    Abstract
    A compact low power circuit for implementation of a direct conversion OQPSK modulator is proposed. The circuit consists of a digital to analog converter, a low pass filter and an up-converter mixer. By embedding these three blocks, the circuit performance is enhanced and the total power consumption is reduced. The mixer is designed base on a Gilbert cell with on chip inductor loads. Instead of transconductance transistors of Gilbert cell, a fully deferential current mode DAC is used and proficiently a low pass filter is embedded between them and therefore the linearity of total system is improved. All of circuits are designed based on 0.18 μm CMOS technology with a single 1.8 volt power... 

    Harmonic content and relaxation resonant frequency of a modulated laser diode

    , Article Scientia Iranica ; Volume 16, Issue 2 D , 2009 , Pages 145-156 ; 10263098 (ISSN) Zandi, H ; Bavafa, M ; Chamanzar, M. R ; Khorasani, S ; Sharif University of Technology
    2009
    Abstract
    In this paper, an analysis of the harmonic contents of the optical output power for an in-plane single mode laser diode is performed, and the results are described in detail. In the first step, the absolute value of power for each harmonic is obtained in terms of various laser diode parameters, and the variations of external parameters, such as modulation current, bias current and frequency, are discussed. The analysis is done by direct solution of the rate equations of an arbitrary laser diode for carrier and photon densities. It is known that the optical power has a nonlinear dependence on frequency, and the maximum optical power of each harmonic is attained in its resonance frequency. The... 

    Novel adaptive Kalman filtering and fuzzy track fusion approach for real time applications

    , Article 2008 3rd IEEE Conference on Industrial Electronics and Applications, ICIEA 2008, Singapore, 3 June 2008 through 5 June 2008 ; 2008 , Pages 120-125 ; 9781424417186 (ISBN) Dehghani Tafti, A ; Sadati, N ; Sharif University of Technology
    2008
    Abstract
    The track fusion combines individual tracks formed by different sensors. Tracks are usually obtained by Kalman Filter (KF), since it is suitable for real-time application. The KF is an optimal linear estimator when the measurement noise has a Gaussian distribution with known covariance. However, in practice, some of the sensors do not have these properties, and the traditional KF is not an optimal estimator. In this paper, a novel adaptive Kalman filter (NAKF) is proposed. In this approach, the measurement noise covariance is adjusted by using an introduced simple mathematical function of one variable, called the degree of matching (DoM), where it is defined on the basis of covariance...