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low-pass-filter
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Total 28 records
A new low power 2-2 cascaded Sigma-Delta modulator with the reduced number of op-amps for GSM transceiver applications
, Article 2003 10th IEEE International Conference on Electronics, Circuits and Systems, ICECS2003, Sharjah, 14 December 2003 through 17 December 2003 ; Volume 1 , 2003 , Pages 268-271 ; 0780381637 (ISBN); 9780780381636 (ISBN) ; Vahidfar, M. B ; Aslanzadeh, H ; Mehrmanesh, S ; Sharif University of Technology
2003
Abstract
A new single-bit cascaded 2-2 σ/δ (Sigma-Delta) modulator with only two op-amps, instead of four ones in conventional modulators, to decrease the static power consumption and area, is designed for GSM transceiver applications. The circuit consists of two new single op-amp, second-order, and low-pass loop filters to achieve a fourth-order quantization noise shaping. The modulator shows 84dB DR (Dynamic Range) for GSM signal bandwidth, while consuming 2.3mW from a 2.5V supply voltage. © 2003 IEEE
TCP retransmission timer adjustment mechanism using system identification
, Article Proceedings of the 2004 American Control Conference (AAC), Boston, MA, 30 June 2004 through 2 July 2004 ; Volume 3 , 2004 , Pages 2328-2332 ; 07431619 (ISSN); 0780383354 (ISBN) ; Rad, A. H. M ; American Automatic Control Council; International Federation of Automation Control, IFAC ; Sharif University of Technology
2004
Abstract
In this paper, the TCP retransmission timer adjustment mechanism is approached from the system's theoretic point of view. TCP uses a simple recursive system identification algorithm to capture both time variant and time invariant Internet behavior and provides a dynamic Round-Trip Time (RTT) predictor. Based on real Internet data collection, it is observed that when the retransmission timer is adjusted by using the proposed predictor instead of the traditional RTT estimator, its performance increases significantly
Synthesis and analysis of sigma-delta modulators employing continuous-time filters
, Article Analog Integrated Circuits and Signal Processing, Dordrecht, Netherlands ; Volume 23, Issue 2 , 2000 , Pages 141-152 ; 09251030 (ISSN) ; Keramat, M ; Kielbasa, R ; Sharif University of Technology
Kluwer Academic Publishers
2000
Abstract
A methodology for analysis and synthesis of lowpass sigma-delta (∑Δ) converters is presented in this paper. This method permits the synthesis of ∑Δ modulators employing continuous-time filters from discrete-time topologies. The analysis method is based on the discretization of a continuous-time model and using a discrete simulator, which is more efficient than an analog simulator. In our analysis approach, the influence of the sample and hold block and non-idealities of the feedback DAC can be systematically modeled by discrete-time systems. Finally, a realistic design of a second-order ∑Δ modulator with a compensation of the non-ideal behavior of the DAC is given. Moreover, simulation...
Comparison of uniform and random sampling for speech and music signals
, Article 2017 12th International Conference on Sampling Theory and Applications, SampTA 2017, 3 July 2017 through 7 July 2017 ; 2017 , Pages 552-555 ; 9781538615652 (ISBN) ; Shahsavari, S ; Marvasti, F ; Sharif University of Technology
Abstract
In this paper, we will provide a comparison between uniform and random sampling for speech and music signals. There are various sampling and recovery methods for audio signals. Here, we only investigate uniform and random schemes for sampling and basic low-pass filtering and iterative method with adaptive thresholding for recovery. The simulation results indicate that uniform sampling with cubic spline interpolation outperforms other sampling and recovery methods. © 2017 IEEE
A new high-speed class-AB current-mode circuit
, Article 2007 IEEE International Symposium on Circuits and Systems, ISCAS 2007, New Orleans, LA, 27 May 2007 through 30 May 2007 ; 2007 , Pages 717-720 ; 02714310 (ISSN) ; Bakhtiar, M. S ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2007
Abstract
this paper presents a new class AB circuit for current-mode signal processing. The proposed circuit provides high-dynamic range, low distortion and accurate definition of quiescent current and it is well suited for high-speed applications. A third-order low-pass filter with a cutoff frequency of 200MHz and 51dB dynamic range is also presented. The Alter consumes 2.7mW from 1.8V supply. © 2007 IEEE
Performance of valveless diffuser micropumps under harmonic piezoelectric actuation
, Article 8th Biennial ASME Conference on Engineering Systems Design and Analysis, ESDA2006, Torino, 4 July 2006 through 7 July 2006 ; Volume 2006 , 2006 ; 0791837793 (ISBN); 9780791837795 (ISBN) ; Saidi, M. H ; Mehrabian, A ; Bazargan, M ; Kenarsari, S. D ; Sharif University of Technology
American Society of Mechanical Engineers
2006
Abstract
Valveless piezoelectric micropumps are in wide practical use due to their ability to conduct particles with absence of interior moving mechanical parts. The objective of this paper is to obtain the fluid flow response to actuation frequency of a passive diffuser valve under harmonic pressures. In this regards a 2D model of a micropump valves and chambers is analyzed. The analysis is performed for 10Kpa back pressure on micropump chamber and actuation frequencies within the range of 1Hz to 10 KHz. Results show the highest velocity in the direction of diffuser axis occurs at the narrow diffuser neck while flow direction reverses every half period. For low frequencies, a parabolic velocity...
A low-power CMOS Gm-C filter for wireless receiver applications with on-chip automatic tuning system
, Article ISCAS 2006: 2006 IEEE International Symposium on Circuits and Systems, Kos, 21 May 2006 through 24 May 2006 ; 2006 , Pages 3810-3813 ; 02714310 (ISSN); 0780393902 (ISBN); 9780780393905 (ISBN) ; Lotfi, R ; Mafinejhad, K ; Tajalli, A ; Mehrmanesh, S ; Sharif University of Technology
2006
Abstract
In this paper, a fourth-order, 3.5-MHz, low-pass elliptic Gm-C filter employing low-noise, low-voltage transconductance amplifiers is presented. A new technique to enhance the linearity of the Gm-C filter is proposed. Furthermore, the nonlinear behavior of the filter caused by nonlinear behavior of transconductors with determined input amplitude is discussed. HSpice simulation results of the 1.8-V filter in a 0.18μm CMOS process show a THD of less than 44dB for 0.6Vpp input signal and an input-referred noise of less than 45 nV/√Hz in worst case. The current consumption of each OTA is 1.5-mA. © 2006 IEEE
Effect of actuation frequency on the performance of diffuser micropumps
, Article 4th International Conference on Nanochannels, Microchannels and Minichannels, ICNMM2006, Limerick, 19 June 2006 through 21 June 2006 ; Volume 2006 B , 2006 , Pages 725-731 ; 0791847608 (ISBN); 9780791847602 (ISBN) ; Ahmadian, M. T ; Sharif University of Technology
2006
Abstract
Valveless piezoelectric micropumps are in wide practical use due to their ability to conduct particles with absence of interior moving mechanical parts. The objective of this paper is to obtain the fluid flow response to actuation frequency of a passive diffuser valve under harmonic pressures. In this regards a 2D model of a micropump valves and chambers is analyzed. The analysis is performed for 10Kpa back pressure on micropump chamber and actuation frequencies within the range of 1 Hz to 10 KHz. Results show the highest velocity in the direction of diffuser axis occurs at the narrow diffuser neck while flow direction reverses every half period. For low frequencies, a parabolic velocity...
Inserting the effects of ion channels in mean field models: Application to generation of anesthetic slow waves
, Article EUROCON 2005 - The International Conference on Computer as a Tool, Belgrade, 21 November 2005 through 24 November 2005 ; Volume I , 2005 , Pages 378-381 ; 142440049X (ISBN); 9781424400492 (ISBN) ; Senhadji, L ; Shamsollahi, M. B ; Sharif University of Technology
2005
Abstract
In this paper, effects of general anesthesia on the electroencephalogram (EEC) has been modeled with an enhanced physiological mean field theory of electrocortical activity. Enhancement is done by inserting two intrinsic ion channels (IKNa and IAR) in Liley's mean field model. In addition to excitatory and inhibitory synapses, intrinsic ion channels can generate or manipulate the brain rhythms. IKNa and IAR can produce slow brain rhythms (delta band frequency) in deep levels of anesthesia. We represent the activities of each mentioned ion channels by cascading a nonlinear function and a first order low pass filter. Linearized and numerical solutions of the modified model show that the power...
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) ; 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...
Design and Implenentation of a Bandpass Delta-sigma Modulator Using High-Q N-path Filter
, M.Sc. Thesis Sharif University of Technology ; Atarodi,Mojtaba (Supervisor) ; Sharifkhani, Mohammad (Co-Supervisor)
Abstract
Delta-Sigma Analog-to-Digital converters have been positioned themselves as robust reliable converters so far. The magic Of extracting high resolutions from low bit ADC has made them popular between designers. Previously, the noise-shaping magic was used in high-resolution applications such as high-quality audio signal converters. However, as the technology scales and proceeds, these converters are approaching RF applications, too. Power and OSR trade-off limits this progress. To increase OSR in bandpass delta-sigma modulators, more power should be consumed to increase the quality factor of loop filters. In this thesis, a systematic approach has been utilized. An n-path filter is employed...
Watermarking based on independent component analysis in spatial domain
, Article Proceedings - 2011 UKSim 13th International Conference on Modelling and Simulation, UKSim 2011, 30 March 2011 through 1 April 2011, Cambridge ; 2011 , Pages 299-303 ; 9780769543765 (ISBN) ; Rahmati, A ; Babaie Zadeh, M ; Sharif University of Technology
2011
Abstract
This paper proposes an image watermarking scheme for copyright protection based on Independent Component Analysis (ICA). In the suggested scheme, embedding is carried out in cumulative form in spatial domain and ICA is used for watermark extraction. For extraction there is no need to access the original image or the watermark, and extraction is carried out only with two watermarked images. Experimental results show that the new method has better quality than famous methods [1], [2], [3] in spatial or frequency domain and is robust against various attacks. Noise addition, resizing, low pass filtering, multiple marks, gray-scale reduction, rotation, JPEG compression, and cropping are some...
An ant-based rate allocation algorithm for media streaming in peer to peer networks: Extension to multiple sessions and dynamic networks
, Article Journal of Network and Computer Applications ; Volume 34, Issue 1 , 2011 , Pages 327-340 ; 10848045 (ISSN) ; Salavati, A. H ; Pakravan, M. R ; Sharif University of Technology
Abstract
In this paper, we introduce a novel algorithm for rate allocation in media streaming P2P networks where multimedia contents are distributed among network members and streamed toward any requesting peer. The proposed algorithm is based on ant-colony optimization. It is capable of handling network dynamism, which is an inherent property of unstructured P2P networks. Another advantage of our algorithm is its ability to get over uncertainties in network state information, particularly the rate of supplying peers that could happen due to lack of accurate measurements. In addition, the suggested method does not rely on any information about the topology of the network. We have investigated both...
On application of high-order compact finite-difference schemes to compressible vorticity confinement method
, Article Aerospace Science and Technology ; Volume 46 , October–November , 2015 , Pages 398-411 ; 12709638 (ISSN) ; Hejranfar, K ; Ebrahimi, M ; Sharif University of Technology
Elsevier Masson SAS
2015
Abstract
The main goal of this study is to assess the application of high-order compact finite-difference schemes for the solution of the Euler equations in conjunction with the compressible vorticity confinement method on both uniform Cartesian and curvilinear grids. Here, the spatial discretization of the governing equations is performed by the fourth-order compact finite-difference scheme and the temporal term is discretized by the fourth-order Runge-Kutta method. To stabilize the numerical solution, appropriate dissipation terms are applied and a detail assessment is performed to study the effects of the values of confinement and dissipation coefficients on the solution to reasonably preserve the...
Reduction of oscillations via fractional order pre-filtering
, Article Signal Processing ; Volume 107 , February , 2015 , Pages 407-414 ; 01651684 (ISSN) ; Sharif University of Technology
Elsevier
2015
Abstract
In this paper, an effective way is proposed for reduction of oscillations in the response of dynamical systems. In this regard, it is analytically shown that the undesirable oscillations in the response of dynamical systems can be reduced using a simple input shaping fractional order filter. The effectiveness of the proposed fractional calculus based technique is numerically verified in reduction of oscillations in a mass-spring-damper system, a low-pass Chebyshev filter, and a PI-controlled two-mass drive system
Robust image watermarking using independent component analysis
, Article Proceedings - 3rd International Symposium on Information Processing, ISIP 2010, 12 November 2010 through 14 November 2010, Qingdao ; 2010 , Pages 363-367 ; 9780769542614 (ISBN) ; Ghaemmaghami, S ; Sharif University of Technology
2010
Abstract
This paper proposes an image watermarking scheme for copyright protection based on Independent Component Analysis (ICA). In the suggested scheme, we divide the original image into blocks and use the ICA to project the image into a basis with its components as statistically independent as possible. The data embedding is carried out in cumulative form in the ICA basis and also the ICA is used for watermark extraction. The extraction process could be either non-blind, through a straightforward procedure, or blind, via a tricky method we propose. Experimental results show that the new method outperforms some well-known image watermarking methods [1], [2], [3] in spatial or frequency domain and...
A variational method for designing adaptive bandlimited wavelets
, Article Signal, Image and Video Processing ; Volume 3, Issue 4 , 2009 , Pages 363-374 ; 18631703 (ISSN) ; Mirzaee, S. M. A ; Sharif University of Technology
2009
Abstract
This paper proposes a new method of estimating an orthogonal bounded spectrum wavelet from a given signal. The method is based on minimizing the distance of the wavelet and the given signal in the sense of the metric of the L2 space. In this method, the amplitude and phase of the mother wavelet are optimized simultaneously. The Lagrange multipliers technique is applied to consider the constraints due to the bounded spectrum wavelet and orthogonality conditions. The variational method reduced the optimal matching problem to the solution of a set of functional equations for the amplitude and phase of the optimal-matched bandlimited wavelet spectrum. Continuous functional equations are written...
A variational method for designing wavelets to match a specified signal
, Article Signal Processing ; Volume 88, Issue 10 , 2008 , Pages 2417-2424 ; 01651684 (ISSN) ; Izadnia, S ; Vahedi, M ; Sharif University of Technology
Elsevier
2008
Abstract
In this paper, we have developed an efficient method for obtaining an orthonormal wavelet that is matched to a given signal. The error between the wavelet and the given signal is minimized subject to the constraints of the amplitude and phase of the band-limited wavelet spectrum. To consider the constraints of the minimization problem, the Lagrange multipliers technique is applied. Variational method reduced the optimal matching problem to the solution of a set of functional equations for the amplitude and phase of the wavelet spectrum. Continuous functional equations were written in terms of Fourier coefficients of the phase of the transfer function of the quadrature low pass filter at the...
A fast vacuum ARC detection method based on the neural network data fusion algorithm for the high-voltage DC power supply of vacuum tubes.رر
, Article IEEE Transactions on Plasma Science ; Volume 49, Issue 1 , 2021 , Pages 476-485 ; 00933813 (ISSN) ; Kaboli, S ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2021
Abstract
Vacuum arc is one of the most important failure factors of the vacuum tubes. The amount of delivered energy from the high-voltage dc power supply to the vacuum tube is an important issue during the vacuum arc in the tube. Vacuum arc acts as a short-circuit fault (SCF) at the power supply output. The majority of converters use a single current sensor to measure only the converter output current for detecting the SCF. However, the sensor may provide unreliable data because of the noise effect. Application of a low-pass filter reduces the noise effect. Regarding the delay of the low-pass filter, the interval of arc detection increases and more energy is delivered to the tube. In this article, a...
A robust machine learning structure for driving events recognition using smartphone motion sensors
, Article Journal of Intelligent Transportation Systems: Technology, Planning, and Operations ; 2022 ; 15472450 (ISSN) ; Taheri Sarteshnizi, I ; Samimi, A ; Sarvi, M ; Sharif University of Technology
Taylor and Francis Ltd
2022
Abstract
Driving behavior monitoring by smartphone sensors is one of the most investigated approaches to ameliorate road safety. Various methods are adopted in the literature; however, to the best of our knowledge, their robustness to the prediction of new unseen data from different drivers and road conditions is not explored. In this paper, a two-phase Machine Learning (ML) method with taking advantage of high-pass, low-pass, and wavelet filters is developed to detect driving brakes and turns. In the first phase, accelerometer and gyroscope filtered time series are fed into Random Forest and Artificial Neural Network classifiers, and the suspicious intervals are extracted by a high recall. Following...