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amplitude-modulation
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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...
Design of Low Phase Noise DCO in All Digital Frequency Synthesizers
, M.Sc. Thesis Sharif University of Technology ; Atarodi, Mojtaba (Supervisor)
Abstract
A new class of design has been introduced in the RF circuits and Frequency Synthesizers, which is based on the digital circuits. Implementation of the digital synthesizers suppresses the need to use loop filter and thus reduces the loop lock time. In this thesis different topologies of digitally controlled oscillators using inductor and capacitor tank and all digital architectures used in high frequency all digital synthesizers in 0.18um CMOS technology has been inspected and simulated. Novel techniques introduced to improve the ring oscillator-based design’s specifications which doesn’t need inductor. Using the introduced techniques, the phase noise has been lessened acceptably with respect...
Simply decoded efficient full-rate space-time block codes over correlated Rician fading channels
, Article IET Communications ; Volume 8, Issue 10 , 3 July 2014 , Pages 1684-1695 ; Pilaram, H ; Mohammadi, A ; Sharif University of Technology
Abstract
A novel technique is presented to design efficient full-rate space-time block codes (STBCs) over correlated Rician fading channels. The authors first derive a formula for the achievable information rate of a linear dispersion coded multi-input single-output system as a function of correlation at the transmitter in a Rician fading channel. In addition, the authors obtain the bit-error-rate (BER) equations for this system, when multiple phase shift keying and multiple quadrature amplitude modulation schemes are used at the transmitter. Therefore with regard to derived formulae and using a genetic algorithm, a method is presented to construct STBCs over correlated Rician fading channels. The...
Analysing of binary PAM systems in digital communication
, Article International Conference on Communication Technology Proceedings, ICCT ; 2012 , Pages 1240-1246 ; 9781467321013 (ISBN) ; Bastani, M. H ; Sharif University of Technology
2012
Abstract
In this era of digital communication systems, different factors are included in efficiency of a transceiver system. Binary PAM systems are one of these transceiver systems. Many aspects of such a system has been considered yet but this field needs more research on because this is the base of any communication system. In this paper, effects of transmitter and receiver filters, noise, duty-cycle and time mismatch between transmitter and receiver in a binary baseband PAM transceiver system is analyzed. Simulation is performed to analyze the above effects on a typical communication system with 10 bits of transmit. MATLAB software is being employed for simulations
Reconfigurable infinite impulse response (IIR) microwave-photonic filter with controllable selectivity using tunable delay line
, Article Conference on Millimeter-Wave and Terahertz Technologies, MMWaTT, 24 December 2012 through 26 December 2012 ; December , 2012 , Pages 37-39 ; 21570965 (ISSN) ; 9781467349567 (ISBN) ; Jamshidi, K ; Akbari, M ; Sharif University of Technology
2012
Abstract
A tunable IIR microwave-photonic filter (MPF) with controllable selectivity is implemented using an electrically tunable delay line. The proposed method has been experimentally tested and verified. An IIR Microwave-Photonic filter with variable Q factor in the range of 238 - 257 is realized
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...
Tip and sample flexibility effects on tapping mode (amplitude modulation) AFM measurements
, Article Micro and Nano Letters ; Volume 6, Issue 12 , December , 2011 , Pages 1023-1028 ; 17500443 (ISSN) ; Meghdari, A ; Sharif University of Technology
2011
Abstract
This Letter is devoted to the investigation of the tip, substrate and particle flexibility effects on the elastic deformation, the maximum repulsive force and the topography images in tapping mode (amplitude modulation) atomic force microscopy (TM-AFM). Several quantitative comparisons among the different models are presented and the effects of the elastic deformations on TM-AFM measurement are investigated
Blind source separation of discrete finite alphabet sources using a single mixture
, Article IEEE Workshop on Statistical Signal Processing Proceedings, 28 June 2011 through 30 June 2011, Nice ; June , 2011 , Pages 709-712 ; 9781457705700 (ISBN) ; Babaie Zadeh, M ; Samadi, S ; Jutten, C ; Sharif University of Technology
2011
Abstract
This paper deals with blind separation of finite alphabet sources where we have n sources and only one observation. The method is applied directly in time (spatial) domain and no transformation is needed. It follows a two stage procedure. In the first stage the mixing coefficients are estimated, and in the second stage the sources are separated using the estimated mixing coefficients. We also study restrictions of this method and conditions for which its performance is acceptable. Simulation results are presented to show the ability of this method to source separation in images and pulse amplitude modulation (PAM) signals
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...
Simulation of imaging in tapping-mode atomic-force microscopy: A comparison amongst a variety of approaches
, Article Journal of Physics D: Applied Physics ; Volume 44, Issue 7 , February , 2011 ; 00223727 (ISSN) ; Mahboobi, S. H ; Meghdari, A ; Sharif University of Technology
2011
Abstract
Models capable of accurate simulation of microcantilever dynamics coupled with complex tip-sample interactions are essential for interpretation and prediction of the imaging results in amplitude modulation or tapping-mode atomic-force microscopy (AM-AFM or TM-AFM). In this paper, four approaches based on combinations of lumped and finite element methods for modelling of cantilever dynamics, and van derWaals and molecular dynamics for modelling of tip-sample interactions, are used to simulate the precise imaging by AM-AFM. Based on the simulated imaging and force determination, the efficiency of different modelling schemes is evaluated. This comparison is performed considering their...
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...
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...
A frequency domain proof for the equivalence of the maximally flat FIR fractional delay filter and the Lagrange interpolator
, Article Digital Signal Processing: A Review Journal ; Volume 21, Issue 1 , 2011 , Pages 13-16 ; 10512004 (ISSN) ; Sharif University of Technology
Abstract
One of the most important properties of the maximally flat (MF) FIR fractional delay (FD) filter is its equivalence with the Lagrange interpolator for uniformly sampled signals. In this article, to provide the required background for the reader, we first propose a straightforward algebraic proof for this equivalence. This proof is given by simply demonstrating that the system of linear equations governing the maximally flatness property of this filter is the same as the one from which the coefficients of the Lagrange interpolator are computed. We then present the main contribution of the paper, which is a frequency domain proof for the same equivalence. In contrast with its classic...
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...
Fast maximum-likelihood decoder for quasi-orthogonal space-time block code
, Article Mathematical Problems in Engineering ; Volume 2015 , 2015 ; 1024123X (ISSN) ; Talebi, S ; Sharif University of Technology
Hindawi Publishing Corporation
2015
Abstract
Motivated by the decompositions of sphere and QR-based methods, in this paper we present an extremely fast maximum-likelihood (ML) detection approach for quasi-orthogonal space-time block code (QOSTBC). The proposed algorithm with a relatively simple design exploits structure of quadrature amplitude modulation (QAM) constellations to achieve its goal and can be extended to any arbitrary constellation. Our decoder utilizes a new decomposition technique for ML metric which divides the metric into independent positive parts and a positive interference part. Search spaces of symbols are substantially reduced by employing the independent parts and statistics of noise. Symbols within the search...
Linear and nonlinear approaches towards amplitude modulation atomic force microscopy
, Article Current Applied Physics ; Volume 10, Issue 6 , 2010 , Pages 1416-1421 ; 15671739 (ISSN) ; Mahmoodi, S. N ; Jalili, N ; Zohoor, H ; Sharif University of Technology
2010
Abstract
Frequency response behavior of microcantilever is analytically and experimentally investigated in amplitude modulation Atomic Force Microscopy (AFM). AFM microcantilever probe is modeled as a continuous beam, and tip-sample interaction force is considered to include both attractive and repulsive force regimes. The developed model is compared with the linear lumped-parameters model that has been extensively used in the literature so far. Experimental measurements are also provided for the frequency response of a typical microcantilever-sample system to demonstrate the advantages of the developed model over the linear formulation. The results indicate that the nonlinear continuous model is...
Numerical investigation of the performance of a U-shaped pulsating heat pipe
, Article Heat Transfer Engineering ; Volume 31, Issue 14 , Oct , 2010 , Pages 1155-1164 ; 01457632 (ISSN) ; Rasoulian, R ; Shafii, M. B ; Saboohi, Y ; Sharif University of Technology
2010
Abstract
In this research the performance of a U-shaped pulsating heat pipe (PHP) was investigated using numerical methods. This heat pipe consists of two sections: The evaporator is set at the two ends of the pipe, and the middle part of the pipe comprises the condenser section. This heat pipe is a type of open looped pulsating heat pipe. The governing equations are derived analytically from the continuity, momentum, and energy equations and are solved implicitly. In this model, considering the liquid mesh, the rate of convection and boiling heat transfer in the U-shaped PHP, which has not been investigated as of yet, are examined. The effect of the evaporator temperature on the pulse amplitude and...
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...
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...