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amplitude-modulation
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Investigation of the modulation between EEG alpha waves and slow/fast delta waves in children in different depths of Desflurane anesthesia
, Article IRBM ; Volume 31, Issue 1 , 2010 , Pages 55-66 ; 19590318 (ISSN) ; Shamsollahi, M. B ; Tirel, O ; Vosoughi Vahdat, B ; Wodey, E ; Senhadji, L ; Sharif University of Technology
2010
Abstract
Objectives: Investigation of the amplitude modulation of alpha-band EEG oscillations (i.e., grouping of alpha-band activities) by delta-band EEG activities in various depths of anesthesia (DOA). Methods: This modulation, which is a sort of phase dependent amplitude modulation, is studied in 10 children in various depths of Desflurane anesthesia. Two parameters are defined to quantify the modulation: strength of modulation (SOM) and phase of modulation (POM). SOM indicates to what extent delta and alpha activities are related to each other, and POM is the delta phase in which the alpha amplitude is maximal. These parameters are analyzed in different DOA for various formations of delta...
Detection of a band-limited signal using an orthonormal, fully-decimated filter-bank
, Article Scientia Iranica ; Volume 14, Issue 6 , 2007 , Pages 555-565 ; 10263098 (ISSN) ; Tadaion, A. A ; Nayebi, M. M ; Aref, M. R ; Sharif University of Technology
Sharif University of Technology
2007
Abstract
In this paper, two methods are proposed for the detection of a band-limited signal in unknown variance white Gaussian noise. The complex amplitude and the frequency of the signal and the noise variance are assumed as unknown parameters. Using wavelet concepts, an orthonormal, fully-decimated filter-bank is employed to decompose the signal into its subband components. It is shown that, in this process, the noise is also decomposed into orthonormal zero-mean components. In the output, if a band-limited target signal is present, the respective single subband component (or two components in marginal cases) containing the target signal presents a non-zero mean. The presence of a non-zero mean...
Adapting power for BER improvement in wireless channels
, Article 8th ACM Symposium on Modeling, Analysis and Simulation of Wireless and Mobile Systems, Montreal, Que., 10 October 2005 through 13 October 2005 ; Volume 2006 , 2006 , Pages 278-281 ; 1595931880 (ISBN); 9781595931887 (ISBN) ; Pakravan, M. R ; Hossein Khalaj, B ; Sharif University of Technology
2006
Abstract
Adaptive transmission is an effective way to improve the performance of communication links in time-varying channel environments. Former works use this technique to maximize the throughput; but we exploit it to minimize BER in a system with diversity reception. We do so by adapting power in response to the channel variations. We use analytical methods to derive our results. These expressions can be used for any type of channel fading and any modulation scheme. We then apply this method to a special case of 4-QAM over Rayleigh channel with MRC reception. Copyright 2005 ACM
Comparison of the smart antenna architectures for OFDM-WLAN systems in a rich multipath environment based on a spatio-temporal channel model
, Article 2005 IEEE 16th International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC 2005, Berlin, 11 September 2005 through 14 September 2005 ; Volume 1 , 2005 , Pages 97-101 ; 3800729091 (ISBN); 9783800729098 (ISBN) ; Shishegar, A. A ; Hojjat, N ; Dadashzadeh, G ; Boghrati, B ; Mehrtash, A ; Sharif University of Technology
2005
Abstract
The smart antenna technique as a method of improving the physical layer performance of OFDM WLANs is studied. For this purpose, a comparison of the smart antenna architectures for IEEE802.11a WLAN system using pre-FFT and post-FFT array processing with different parameters is represented. Simulations are performed on a new Simulink model for IEEE802.11a system using a spatio-temporal channel modeling which is based on the measured wideband channels in the 5GHz band. Raw bit-error-rate performance for QPSK/16QAM modulations at LOS and NLOS channel scenarios are evaluated and compared. © 2005 IEEE
The effect of added mass fluctuation on heave vibration of TLP
, Article International Journal of Engineering, Transactions B: Applications ; Volume 18, Issue 3 , 2005 , Pages 219-228 ; 1728-144X (ISSN) ; Golafshani, A. A ; Seif, M. S ; Sharif University of Technology
Materials and Energy Research Center
2005
Abstract
The resulting motion in waves can be considered as a superposition of the motion of the body in still water and the forces on the restrained body. In this study the effect of added mass fluctuation on vertical vibration of TLP in the case of vibration in still water for both free and forced vibration subjected to axial load at the top of the leg is presented. This effect is more important when the amplitude of vibration is large. Also this is important in fatigue life study of tethers. The structural model used here is very simple. Perturbation method is used to formulate and solve the problem. First and second order perturbations arc used to solve the free and forced vibration respectively
Exact symbol and bit error probabilities of linearly modulated signals with maximum ratio combining diversity in frequency non-selective Rician and Rayleigh fading channels
, Article IET Communications ; Volume 5, Issue 1 , January , 2011 , Pages 12-26 ; 17518628 (ISSN) ; Sharif University of Technology
2011
Abstract
The exact symbol and bit error probabilities of linearly modulated signals in frequency non-selective Rician fading channels with Lth diversity branches are derived, where coherent detection with maximum ratio combining (MRC) is used at the receiver. For performance evaluation, the multiplicative distortion is combined with the additive Gaussian noise and form an additive noise is formed. This method allows computing the exact symbol and bit error probabilities of M-ary phase shift keying (M-PSK), M-ary quadrature amplitude modulation (M-QAM), M-ary amplitude modulation (M-AM) and M-ary amplitude modulation phase modulation (M-AMPM) for any arbitrary bit mappings. The results contain several...
Nonlinear dynamic analysis of a V-shaped microcantilever of an atomic force microscope
, Article Applied Mathematical Modelling ; Volume 35, Issue 12 , 2011 , Pages 5903-5919 ; 0307904X (ISSN) ; Rahaeifard, M ; Ahmadian, M. T ; Sharif University of Technology
Abstract
This paper is devoted to investigate the nonlinear behaviors of a V-shaped microcantilever of an atomic force microscope (AFM) operating in its two major modes: amplitude modulation and frequency modulation. The nonlinear behavior of the AFM is due to the nonlinear nature of the AFM tip-sample interaction caused by the Van der Waals attraction/repulsion force. Considering the V-shaped microcantilever as a flexible continuous system, the resonant frequencies, mode shapes, governing nonlinear partial and ordinary differential equations (PDE and ODE) of motion, boundary conditions, frequency and time responses, potential function and phase-plane of the system are obtained analytically. The...
Modeling Electrical Activities of the Brain and Analysis of the EEG in General Anesthesia
, M.Sc. Thesis Sharif University of Technology ; Shamsollahi, Mohammad Bagher (Supervisor)
Abstract
In this thesis, an enhanced local mean-field (MF) model that is suitable for simulating the electroencephalogram (EEG) in different depths of anesthesia is presented. The main building elements of the model (e.g. excitatory and inhibitory populations) are taken from two pioneer MF models designed by Steyn-Ross et al and Bojak & Liley, and then a new slow ionic mechanism is included in the main model. Generally, in mean-field models, some sigmoid-shape functions determine firing rates of neural populations according to their mean membrane potentials. In the enhanced model, the sigmoid function corresponding to excitatory population is redefined to be also a function of the slow ionic...
Optimized decision feedback equalizer and comparison with MLSE algorithm for GSM channel
, Article Proceedings - 2011 UKSim 13th International Conference on Modelling and Simulation, UKSim 2011, 30 March 2011 through 1 April 2011, Cambridge ; 2011 , Pages 482-487 ; 9780769543765 (ISBN) ; Rahmati, A ; Hajisami, A ; Sharif University of Technology
2011
Abstract
In this paper, we present basic equation of efficient recursive least square algorithm based on GMSK modulation by linear superposition of amplitude modulated pulses for reduction complexity in equalizer. In this here, the DFE method be improved using of signal processing technique and soft decision which is called "generalized DFE or GDFEmethodquot;. We compare the performance and complexity GDFE with MLSE method for different channels used in GSM systems. The GDFE differs from the conventional DFE in its tap values and value of tap feedback filter related with channel length, which discussed in simulation result. Our simulation results, obtained for fading multi path channels, show that...
A robust algorithm based on wavelet transform for recognition of binary digital modulations
, Article 2015 38th International Conference on Telecommunications and Signal Processing, TSP 2015, 9 July 2015 through 11 July 2015 ; July , 2015 , Pages 508-512 ; 9781479984985 (ISBN) ; Pezeshk, A. M ; Behnia, F ; Molnar K ; Herencsar N ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2015
Abstract
Automatic Modulation Recognition (AMR) of communication signals has been an important theme in wireless communication systems. Recently, digital modulation recognition has been considered remarkably, due to the vast application of this kind of AMR technique in spectrum sensing and cognitive radio. In this paper, we propose a wavelet-based algorithm for recognition of binary digital modulation schemes including BASK, BFSK and BPSK in presence of Additive White Gaussian Noise (AWGN). In this algorithm, Haar Wavelet Transform (HWT) of the received signal is compared to templates and the similarity of them are measured. Experimental results show a perfect classification of binary digital...
A high-throughput VLSI architecture for hard and soft SC-FDMA MIMO detectors
, Article IEEE Transactions on Circuits and Systems I: Regular Papers ; Volume 62, Issue 3 , January , 2015 , Pages 761-770 ; 15498328 (ISSN) ; Shabany, M ; Gulak, G ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2015
Abstract
This paper introduces a novel low-complexity multiple-input multiple-output (MIMO) detector tailored for single-carrier frequency division-multiple access (SC-FDMA) systems, suitable for efficient hardware implementations. The proposed detector starts with an initial estimate of the transmitted signal based on a minimum mean square error (MMSE) detector. Subsequently, it recognizes less reliable symbols for which more candidates in the constellation are browsed to improve the initial estimate. An efficient high-throughput VLSI architecture is also introduced achieving a superior performance compared to the conventional MMSE detectors with less than 28% added complexity. The performance of...
Extension of depth of field using amplitude modulation of the pupil function for bio-imaging
, Article Proceedings of SPIE - The International Society for Optical Engineering, 6 April 2010 through 8 April 2010 ; Volume 7690 , May , 2010 ; 0277786X (ISSN) ; 9780819481542 (ISBN) ; Bagheri, S ; Mehrany, K ; Javidi, B ; Sanchez, E ; Martinez Corral, M ; Sharif University of Technology
2010
Abstract
In this paper we present a novel approach to generate images of extended depth of field (DOF) without compromising the lateral resolution to support realization of three-dimensional imaging systems such as integral imaging. In our approach in extending DOF, we take advantage of the spatial frequency spectrum of the object specific to the task in hand. The pupil function is thus engineered in such a fashion that the modulation transfer function (MTF) is maximized only in these selected spatial frequencies. We extract these high energy spatial frequencies using PCA method. The advantage of our approach is illustrated using an amplitude modulation and a phase modulation example. In these...
A hybrid algorithm for prediction of varying heart rate motion in computer-assisted beating heart surgery
, Article Journal of Medical Systems ; Volume 42, Issue 10 , 2018 ; 01485598 (ISSN) ; Farahmand, F ; Vossoughi, G ; Alizadeh Ghavidel, A ; Sharif University of Technology
Springer New York LLC
2018
Abstract
An essential requirement for performing robotic assisted surgery on a freely beating heart is a prediction algorithm which can estimate the future trajectory of the heart in the varying heart rate (HR) conditions of real surgery with a high accuracy. In this study, a hybrid amplitude modulation- (AM) and autoregressive- (AR) based algorithm was developed to enable estimating the global and local oscillations of the beating heart, raised from its major and minor physiological activities. The AM model was equipped with an estimator of the heartbeat frequency to compensate for the HR variations. The RMS of the prediction errors of the hybrid algorithm was in the range of 165–361 μm for the...
Efficiency enhancement of time-modulated arrays with optimized switching sequences
, Article IEEE Transactions on Antennas and Propagation ; Volume 66, Issue 7 , July , 2018 , Pages 3411-3420 ; 0018926X (ISSN) ; Fakharzadeh, M ; Akbari, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2018
Abstract
The conventional time-modulated arrays (TMAs) have a low radiation efficiency, since each antenna turns off at specific time slots. In this paper, first, the efficiency of TMA is investigated analytically. Next, the optimized switching sequences are proposed to enhance the radiation efficiency of a specific sideband, while preserving the level of the other sidebands. The practical hardware limitations are considered in the switching sequence design. Moreover, a low-cost flexible eight-element printed dipole array operating at 1.2-1.4 GHz is implemented to verify the proposed algorithms. The measured radiation patterns indicate that by applying the proposed sequences, the TMA efficiency...
The dependence of the moving sonoluminescing bubble trajectory on the driving pressure
, Article Journal of the Acoustical Society of America ; Volume 126, Issue 5 , 2009 , Pages 2266-2272 ; 00014966 (ISSN) ; Rezaei Nasirabad, R ; Galavani, Z ; Sharif University of Technology
2009
Abstract
With a complete accounting of hydrodynamic forces on the translational-radial dynamics of a moving single-bubble sonoluminescence, temporal evolution of the bubble trajectory is investigated. In this paper, by using quasi-adiabatic evolution for the bubble interior, the bubble peak temperature at the bubble collapse is calculated. The peak temperature changes because of the bubble translational motion. The numerical results indicate that the strength of the bubble collapse is affected by its translational movement. At the bubble collapse, translational movement of the bubble is accelerated because of the increase in the added mass force on the bubble. It is shown that the magnitude of the...
Equivalence of the Lagrange interpolator for uniformly sampled signals and the scaled binomially windowed shifted sinc function
, Article Digital Signal Processing: A Review Journal ; Volume 19, Issue 5 , 2009 , Pages 838-842 ; 10512004 (ISSN) ; Sharif University of Technology
2009
Abstract
The maximally flat (MF) fractional delay (FD) filter which is in fact a Lagrange interpolator for uniformly sampled signals, has previously been shown to be equal to the scaled binomially windowed shifted version of the sinc function; the ideal interpolation kernel for band-limited signals. In this paper, another proof for this equivalence is presented. Unlike its counterparts available in the literature, the proof given here is neither strictly algebraic, nor deploys the explicit coefficient formulas of the MFFD filter. It follows a frequency domain approach based on the definition of this filter instead, and aims to provide more insight into the corresponding equivalence. © 2009 Elsevier...
Selection of excitation signal waveform for improved performance of wound-rotor resolver*
, Article 10th International Power Electronics, Drive Systems and Technologies Conference, PEDSTC 2019, 12 February 2019 through 14 February 2019 ; 2019 , Pages 160-165 ; 9781538692547 (ISBN) ; Alipour Sarabi, R ; Nasiri Gheidari, Z ; Tootoonchian, F ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
Wound-Rotor (WR) resolvers are similar to two-phase synchronous generators. Their difference is related to the excitation signal. While DC voltage is used for exciting synchronous generator, high frequency AC voltage is employed for that of resolver. The common waveform for excitation signal of resolver is sinusoidal voltage. However, preparing the high frequency sinusoidal voltage in the resolver to digital converter (RDC) is always a challenge. Therefore, in this paper different high frequency AC waveforms are applied as the excitation signal of the resolver and the estimated position, resulted from RDC, is discussed. The aim of this work is to find an appropriate excitation waveform that...
Analysis of the effect of ageing on rising edge characteristics of the photoplethysmogram using a modified windkessel model
, Article Cardiovascular Engineering ; Volume 7, Issue 4 , 2007 , Pages 172-181 ; 15678822 (ISSN) ; Chellappan, K ; Mohd Ali, M. A ; Singh, H ; Sharif University of Technology
2007
Abstract
Ageing is one of the main contributing factors towards increasing arterial stiffness, leading to changes in peripheral pulses propagation. Therefore the characteristics of the photoplethysmogram (PPG) pulse, especially the rising edge and peak position, are greatly affected. In this study, the PPG pulse rising edge and corresponding peak position have been investigated non-invasively in human subjects as a function of age. Fifteen healthy subjects were selected and grouped in five age intervals, from 20 to 59 years, based on their comparable systolic-diastolic blood pressure and PPG amplitude. As expected, the peripheral pulse shows a steep rise and early peak in younger subjects. With age,...
Effects of higher oscillation modes on TM-AFM measurements
, Article Ultramicroscopy ; Volume 111, Issue 2 , 2011 , Pages 107-116 ; 03043991 (ISSN) ; Meghdari, A ; Sharif University of Technology
Abstract
The finite element method and molecular dynamics simulations are used for modeling the AFM microcantilever dynamics and the tip-sample interaction forces, respectively. Molecular dynamics simulations are conducted to calculate the tip-sample force data as a function of tip height at different lateral positions of the tip with respect to the sample. The results demonstrate that in the presence of nonlinear interaction forces, higher eigenmodes of the microcantilever are excited and play a significant role in the tip and sample elastic deformations. Using comparisons between the results of FEM and lumped models, how some aspects of the system behavior can be hidden when the point-mass model is...
Optimization of Tribenuron-methyl determination by differential pulse polarography using experimental design
, Article Analytical Methods ; Volume 2, Issue 1 , 2010 , Pages 41-48 ; 17599660 (ISSN) ; Ghassempour, A ; Fakhari, A. R ; Jalali Heravi, M ; Aboul Enein, H. Y ; Sharif University of Technology
Abstract
Differential pulse polarography (DPP) was applied for the determination of the herbicide Tribenuron-methyl (TBM). This is a first study for various parameters affecting the reduction peak current were simultaneously optimized using experimental design and these results are different from other reports. The effect of factors such as voltage step, voltage step time, pulse amplitude, pulse time, sample pH, concentration of the supporting electrolyte and the mercury drop size were assessed by means of a (27-2) fractional factorial design. It was found that the effects and interactions of four out of seven factors were significant. Consequently, a central composite design (CCD) with four factors,...