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    Wide-band VHF nulling by five elements spiral array antenna

    , Article ITST 2006 - 2006 6th International Conference on ITS Telecommunications, Proceedings, Chengdu, 21 June 2006 through 23 June 2006 ; 2006 , Pages 446-448 ; 0780395867 (ISBN); 9780780395862 (ISBN) Jafargholi, A ; Mousavi, M ; Emadi, M ; Nayebi, M. M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2006
    Genetic algorithm for optimization of beam forming in spiral array antenna is used. The goal is to achieve a -20 dB in null over the wide frequency band. Our simulation shows -20 dB over 75 MHz Null Band width, in VHF band. © 2006 IEEE  

    Exposure of the human brain to an electromagnetic plane wave in the 100-1000 MHz frequency range for potential treatment of neurodegenerative diseases

    , Article IET Microwaves, Antennas and Propagation ; Volume 6, Issue 14 , 2012 , Pages 1565-1572 ; 17518725 (ISSN) Khaleghi, A ; Eslampanah Sendi, M.S ; Chávez Santiago, R ; Mesiti, F ; Balasingham, I ; Sharif University of Technology
    Radio signals can induce an electric field inside the brain, which might be potentially beneficial in the treatment of neurodegenerative diseases. For instance, a new method for the treatment of Alzheimer's disease in mice through the exposure to the radiation of mobile phones has been successfully demonstrated. In the light of these results, studying the induction of an electric field in the human brain through the controlled exposure to radio signals is of paramount importance for the eventual development of similar treatment techniques in humans. In this study, the authors study the radio signals in 100-1000 MHz as a means for inducing an electric field into the human brain in a... 

    Detection of fast ripples using Hidden Markov Model

    , Article 2014 21st Iranian Conference on Biomedical Engineering, ICBME 2014, 26 November 2014 through 28 November 2014 ; November , 2014 , Pages 348-352 ; 9781479974177 (ISBN) Nazarimehr, F ; Montazeri, N ; Shamsollahi, M. B ; Kachenoura, A ; Wendung, F ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2014
    Studies show that High frequency oscillations (HFOs) can be used as a reliable biomarker of epileptogenic zone, thus many algorithms have been proposed to detect HFOs. Among the wide variety of HFOs, fast ripples (FRs) are important transient oscillations occurring in the frequency band ranging from 250 Hz to 600 Hz. The automatic detection of FRs can be degenerated by the presence of some 'pulse-like' events (commonly, the component of interictal epileptic spikes) associated with an increase of the signal energy in the high frequency bands, exactly as in the case of real FRs. The goal of this study is to propose a new method for automatic detection of fast ripples by using Hidden Markov... 

    Indoor ultrawideband propagation modelling using Chebyshev interpolation in 60 GHz band based on ray tracing technique

    , Article Conference on Millimeter-Wave and Terahertz Technologies, MMWaTT, 30 December 2014 through 1 January 2015 ; Volume 2015-March , December-January , 2015 ; 21570965 (ISSN) ; 9781479965915 (ISBN) Boozari, M ; Shishegar, A. A ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2015
    An efficient ray tracing technique for channel modeling of an ultrawideband signal in 60 GHz band is introduced. In the usual method, field calculations at many frequencies must be done where has a high computational cost. We have introduced a novel method using Chebyshev polynomials interpolation to reduce the computational cost. Some propagation parameters such as gain and root mean square (RMS) delay spread are obtained and compared to the other method  

    A new link-level simulation procedure of wideband MIMO radio channel for performance evaluation of indoor WLANs

    , Article Progress in Electromagnetics Research ; Volume 83 , 2008 , Pages 13-24 ; 10704698 (ISSN) Golparvar Roozbahani, M ; Jedari, E ; Shishegar, A. A ; Sharif University of Technology
    Electromagnetics Academy  2008
    Inspired by the requirement of proper link simulation methods in performance analysis of communication systems, we present in this paper a recipe for channel implementation in simulation environments. Our focus here is the indoor applications of wireless local-area networks (WLANs). Specifically, we describe a procedure that beginning with statistical description of the channel impulse response leads to an efficient multi-input multi-output (MIMO) channel simulating method for arbitrary antenna configurations at both ends. A sample set of distributions for model parameters are also provided at the 5-GHz band, which is the operating frequency band of IEEE 802.11a, HIPERLAN/2, and the emerging... 

    Conference room reverberation time correction using helmholtz resonators lined with absorbers

    , Article Shock and Vibration ; Vol. 2014, issue , May , 2014 Namvar Arefi, H ; Ghiasi, S. M. A ; Ghaffari, S. M ; Ramezanghorbani, F ; Sharifpour, S ; Irajizad, P ; Ghoreishi Langroudi, S. D ; Amjadi, A ; Sharif University of Technology
    Echo and sound resonance in a conference room cause obscure speech and make listeners tired. Thus, the acoustical properties of a conference room are vitally important. The conference room 412 at Sharif University Physics Department failed to meet basic acoustical standards. The aim of this research is to improve reverberation time (RT) of the conference room using Helmholtz resonators with defined dimensions, diffusers, and sound absorbers. Helmholtz resonators are widely used to absorb sound noise especially at low frequencies. They are particularly useful when noise has a narrow-frequency band. One of the advantages of using Helmholtz resonators is their capacity to be tuned on different... 

    EEG-based functional brain networks: Hemispheric differences in males and females

    , Article Networks and Heterogeneous Media ; Volume 10, Issue 1 , March , 2015 , Pages 223-232 ; 15561801 (ISSN) Jalili, M ; Sharif University of Technology
    American Institute of Mathematical Sciences  2015
    Functional connectivity in human brain can be represented as a network using electroencephalography (EEG) signals. Network representation of EEG time series can be an efficient vehicle to understand the underlying mechanisms of brain function. Brain functional networks whose nodes are brain regions and edges correspond to functional links between them are characterized by neurobiologically meaningful graph theory metrics. This study investigates the degree to which graph theory metrics are sex dependent. To this end, EEGs from 24 healthy female subjects and 21 healthy male subjects were recorded in eyes-closed resting state conditions. The connectivity matrices were extracted using... 

    Capacity of a class of symmetric relay networks with orthogonal components

    , Article IET Communications ; Volume 4, Issue 18 , 2010 , Pages 2181-2186 ; 17518628 (ISSN) Ghabeli, L ; Aref, M. R ; Sharif University of Technology
    In this study, the authors extend the concept of relay channel with orthogonal components to define a class of symmetric relay networks with orthogonal components named symmetric orthogonal relay network. In the defined network, the channels diverge from each node sender use different frequency bands whereas the channels converge to each node receiver use the same frequency band. This structure is very well understood in half-duplex transmission systems where the relays cannot send and receive at the same time or over the same frequency band. The authors show that the unicast capacity of the defined network is equal to the cut-set bound. In the achievability proof, the authors take advantage... 

    Design of a hybrid spoof plasmonic sub-terahertz waveguide with low bending loss in a broad frequency band

    , Article Optics Express ; Volume 25, Issue 6 , 2017 , Pages 6860-6873 ; 10944087 (ISSN) Khosravi Moghaddam, M. A ; Ahmadi Boroujeni, M ; Sharif University of Technology
    OSA - The Optical Society  2017
    The effect of dielectric cladding on the waveguiding characteristics of an array of metallic pillars on a metal plane in the sub-terahertz band is explored. Firstly, a 2D structure made up of a metallic grating of infinite lateral width with various dielectric overlays is analytically studied to get more insight into the problem. Then the ideas inferred from the 2D structure are applied to the realistic 3D structure that has a finite lateral width. It is shown that by proper design of the dielectric medium surrounding the metallic structure the modal field confinement can be enhanced in a broad frequency band resulting in a low bending loss. Especially, by integrating the pillars into a... 

    VHF-LB SDR phased array jamming resistant antenna

    , Article ITST 2006 - 2006 6th International Conference on ITS Telecommunications, Proceedings, Chengdu, 21 June 2006 through 23 June 2006 ; 2006 , Pages 442-445 ; 0780395867 (ISBN); 9780780395862 (ISBN) Jafargholi, A ; Emadi, M ; Esmi, N ; Mousavi, M ; Nayebi, M. M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2006
    Genetic algorithm for optimization of beam forming in linear array antenna is used. The goal is to achieve a -30 dB null depth in pattern, with null steering capability over the frequency band. The simulation result is -85 dB that the SuperNEC results accepted this result by -56 dB Null Depth. Software Define Radio (SDR) Technology and digital I/Q modulator are used to implement the system. © 2006 IEEE  

    A new wideband MIMO channel model for simulating 5-GHz band indoor WLANs

    , Article 2006 IEEE 64th Vehicular Technology Conference, VTC-2006 Fall, Montreal, QC, 25 September 2006 through 28 September 2006 ; 2006 , Pages 2298-2303 ; 15502252 (ISSN); 1424400635 (ISBN); 9781424400638 (ISBN) Jedari, E ; Golparvar Roozbahani, M ; Shishegar, A. A ; Enayati, A. R ; Alihemmati, R ; Sharif University of Technology
    Considerable interest in the indoor applications of wireless local-area networks (WLANs) demands some powerful simulation methods of these systems. Proper modeling of the physical propagation channel is crucial in this context. A novel simulation method for indoor wideband multi-input multi-output (MIMO) channel at the operating frequency band of IEEE 802.11a, HIPERLAN/2, and the emerging IEEE 802.11n standards is presented in this paper which is suitable for performance analysis of MIMO techniques in these systems. The presented model is developed on the basis of a previously proposed channel representation at the same frequency band. Simulation results for MIMO channel capacity are... 

    MRI-PET image fusion based on NSCT transform using local energy and local variance fusion rules

    , Article Journal of Medical Engineering and Technology ; Vol. 38, issue. 4 , 2014 , p. 211-219 Amini, N ; Fatemizadeh, E ; Behnam, H ; Sharif University of Technology
    Image fusion means to integrate information from one image to another image. Medical images according to the nature of the images are divided into structural (such as CT and MRI) and functional (such as SPECT, PET). This article fused MRI and PET images and the purpose is adding structural information from MRI to functional information of PET images. The images decomposed with Nonsubsampled Contourlet Transform and then two images were fused with applying fusion rules. The coefficients of the low frequency band are combined by a maximal energy rule and coefficients of the high frequency bands are combined by a maximal variance rule. Finally, visual and quantitative criteria were used to... 

    Design of Digital Backend of the RFID Reader and Design of Baseband Signal Conditioning Circuits and Simulating RFID System

    , M.Sc. Thesis Sharif University of Technology Jadidnouri, Mohammad (Author) ; Sharif Bakhtiar, Mehrdad (Supervisor)
    In this Thesis, first, UHF RFID Class1 Generation 2 was studied accurately and Required Signaling, Timing and Circuit Parameters for Design Readers in this Band, was Extracted from Standard. an important algorithm for Tags inventory, that Protocol leaves the way of implementation to designer, was introduced and simulated. Also a effective method was presented that detect bit streams received by readers in low SNR. Some parts of Baseband Signal conditioning circuits, including filter and variable gain amplifier, wad designed in 0.18 um CMOS Technology. In Second part, communication protocol between server and readers was introduced with some Scenarios that make communication easier and make... 

    Detection, Characterization and Analysis of Partial Discharge Signals Frequency Spectrum Related to Different Oil Transformer Faults using UHF Antenna

    , M.Sc. Thesis Sharif University of Technology Nasr Azadani, Ali (Author) ; Vakilian, Mehdi (Supervisor)
    One of the electromagnetic methods for partial discharge detection is known as UHF detection. In this method the electromagnetic radiations from PD sources over a wide frequency band of UHF are detected and the related spectrums over the UHF frequency band are captured for diagnostic. The absence of noise in UHF band (300 MHz- 3GHz) is the most important advantage of this method if compared with other electrical PD detection methods. To capture electromagnetic signals and radiations generated by PD sources, application of an electromagnetic sensor, named antenna, is necessary. Therefore one of the goals in this thesis is to select, design, and build a suitable antenna for PD detection.... 

    Radio Receiver Design for Cognitive Radio in The UHF Band

    , M.Sc. Thesis Sharif University of Technology Nikoofard, Ali (Author) ; Fotowat Ahmady, Ali (Supervisor)
    With the ever-increasing communication need for propagating signals in authorized empty bands, the goal of this thesis is based on finding these unused bands and using them,which called Cognitive Radio. In this project, design and implementation of radio frequency building blocks of a receiver in the UHF band (400 to 800 MHz) is performed. In this project, however, the radio frequency building blocks include low noise amplifier, high-frequency quadrature mixers, high-frequency oscillators, tunable low-pass filter,band select filter,phase-locked loop and synthesizer, all of which are introduced, examined and implemented. Moreover, a new method which mitigates the speed limitation is verified.... 

    A harmonic termination technique for single-and multi-band high-efficiency class-F MMIC power amplifiers

    , Article IEEE Transactions on Microwave Theory and Techniques ; Volume 62, Issue 5 , May , 2014 , Pages 1212-1220 ; ISSN: 00189480 Nikandish, G ; Babakrpur, E ; Medi, A ; Sharif University of Technology
    This paper presents a harmonic termination technique for single-and multi-band high-efficiency class-F monolithic microwave integrated circuit (MMIC) power amplifiers (PAs). The harmonic termination network (HTN), realized with the minimum possible number of elements, can be used to terminate an arbitrary number of harmonics in a single-band PA or harmonics of multiple frequencies in a concurrent multi-band PA. The drain and gate bias lines are embedded in the HTNs to obviate the need for RF chokes and reduce the chip area. A single-and a dual-band MMIC PA are designed using the proposed technique and implemented in a 0.25-μm AlGaAs-InGaAs pHEMT technology. The single-band 5.5-GHz PA... 

    Analysis and optimization of wideband tapered directional couplers by DTM method

    , Article Microwave and Optical Technology Letters ; Vol. 56, issue. 8 , August , 2014 , pp. 1795-1798 ; ISSN: 08952477 Ali Sadreghaeni, S. M ; Banai, A ; Mehrany, K ; Sharif University of Technology
    In this article, a novel approach based on differential transfer matrix method is proposed for fast analysis and optimization of wideband planar tapered directional couplers. In this method, both even and odd modes can be analyzed independently to obtain overall scattering matrix. The new method accelerates the optimization time considerably in planar structures. An 8.34 dB tapered coupler in the frequency band of 1-12 GHz is designed and optimized in the form of offset stripline structure. The experimental result shows good agreement with theory  

    Wide-band high-efficiency Ku-band power amplifier

    , Article IET Circuits, Devices and Systems ; Vol. 8, issue. 6 , December , 2014 , p. 583-592 ; 1751858X Yousefi, A ; Medi, A ; Sharif University of Technology
    A 37 dBm power amplifier (PA) is designed on a 0.25 μm optical T-gate pseudomorphic high electron mobility transistor (pHEMT) technology. The design of this two-stage PA along with a step-by-step design procedure is presented in this paper. This methodology can be used for design of PA in different technologies and frequencies. The PA delivers 5 W output power over the frequency band of 13-19 GHz. It shows average power-added efficiency of 37% and large signal gain of 15 dB in measurements which is consistent with simulation results. The output power and efficiency of the realised amplifier reach maximums of 37.6 dBm and 45%, respectively. Considering output power, bandwidth, chip area and... 

    Design and analysis of broadband darlington amplifiers with bandwidth enhancement in GaAs pHEMT technology

    , Article IEEE Transactions on Microwave Theory and Techniques ; Volume 62, Issue 8 , August , 2014 , Pages 1705-1715 ; ISSN: 00189480 Nikandish, G ; Medi, A ; Sharif University of Technology
    This paper presents a bandwidth enhancement technique for broadband Darlington amplifiers. A detailed analysis of the high-frequency performance of the Darlington amplifier and the effect of bandwidth enhancement is provided. A design procedure is also given for broadband feedback Darlington amplifiers with bandwidth enhancement and gain flattening. A single- and a three-stage feedback amplifier with the proposed improvements are designed and implemented in a 0.25-μm Al-GaAs-InGaAs pHEMT technology. The single-stage amplifier provides 6 ± 0.4 dB of small-signal gain in the frequency band of 1-30 GHz. The three-stage amplifier features 17.8 ± 0.8 dB of small-signal gain in the frequency band... 

    Tunable left-handed characteristics of ferrite rectangular waveguide periodically loaded with complementary split-ring resonators

    , Article IEEE Transactions on Magnetics ; Volume 49, Issue 8 , 2013 , Pages 4780-4784 ; 00189464 (ISSN) Ghalibafan, J ; Komjani, N ; Rejaei, B ; Sharif University of Technology
    We propose, for the first time, a tunable left-handed (LH) waveguide consisting of an array of complementary split-ring resonators built on the broad wall of a rectangular waveguide filled with ferrite material. The left-handed behavior is caused by the negative permittivity of the complementary split-ring resonators together with the negative permeability of the transversely magnetized ferrite. The electromagnetic behavior of this structure is studied by means of an equivalent circuit model. From this model, the dispersion relation of the guide is derived and validated numerically by the finite element method. It is shown that this structure has a left-handed frequency band that can be...