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Investigation of the locking bandwidth in linear and circular arrays of mutually coupled oscillators, intended for microwave power combining
, Article IEE Proceedings: Microwaves, Antennas and Propagation ; Volume 152, Issue 6 , 2005 , Pages 441-448 ; 13502417 (ISSN) ; Farzaneh, F ; Ayazian, S ; Sharif University of Technology
2005
Abstract
An array of N weakly coupled oscillators is investigated in two major configurations. The locking bandwidth for linear and circular arrays is assessed through an array coupling matrix, in a worst-case free-running frequency distribution of oscillators. The superior locking bandwidth for circular arrays is demonstrated
Various multirate time-hopping UWB systems and performance evaluation
, Article 2004 IEEE International Symposium on Spread Spectrum Techniques and Applications, ISSSTA 2004, Sydney, 30 August 2004 through 2 September 2004 ; 2004 , Pages 120-124 ; Nasiri Kenari, M ; Sharif University of Technology
2004
Abstract
We consider multirate time-hopping ultra-wideband (TH-UWB) communication systems where each user can have several multirate services. We investigate both constant spreading factor scheme, which uses multicode, and variable spreading factor scheme, which uses constant chip time and variable frame number. For multicode structure, we consider two methods. In the first, one kind of signature (PN) code is used to distinguish users and their diverse services alike. Whereas in the second one different users and different services of the same user are distinguished through two kinds of signature codes, namely PN code and Walsh code, respectively. For variable spreading factor scheme, one signature...
Iterative multiuser receiver for coded MC-FH multiple access systems in the presence of partial-band interference
, Article 2004 IEEE 60th Vehicular Technology Conference, VTC2004-Fall: Wireless Technologies for Global Security, Los Angeles, CA, 26 September 2004 through 29 September 2004 ; Volume 60, Issue 3 , 2004 , Pages 1899-1903 ; 15502252 (ISSN) ; Nasiri Kenari, M ; Sharif University of Technology
2004
Abstract
In this paper, we consider an iterative multiuser receiver for the coded MC-FH system, first introduced in [4], in the presence of partial-band interference. The structure of the receiver consists of two principal parts: multiuser soft input soft output (SISO) detector and SISO channel decoder. When the channel is under the attack of jamming, for optimum detection we propose to add a jamming estimator to multiuser SISO detector. So, the new SISO multiuser detector consists of multiuser likelihood calculator (MULC) and iterative jamming estimator (JE). The numerical results show that the proposed receiver works quite well compared to the ideal receiver which has the perfect channel state...
A new method of phase noise compensation in OFDM
, Article 2003 International Conference on Communications (ICC 2003), Anchorage, AK, 11 May 2003 through 15 May 2003 ; Volume 5 , 2003 , Pages 3443-3446 ; 05361486 (ISSN) ; Nader Esfahani, S ; Eftekhar, A. A ; Sharif University of Technology
2003
Abstract
The local oscillator phase noise can severely affect the performance of OFDM systems. In this paper a new method is presented for compensation of this phase noise. The method is based on the fact that the scattered pilots, which are used for channel estimation, are subject to the same phase error as the OFDM symbols. Least square approach is used to exploit the phase noise information that exists in the scattered pilots and compensate the phase noise on the OFDM symbols. Simulation results show that the method is very effective, especially in high SNR
Bacterial foraging search in unstructured P2P networks
, Article Canadian Conference on Electrical and Computer Engineering ; 2014 ; Pakravan, M. R ; Sharif University of Technology
Abstract
In this paper, a new search algorithm in heterogeneous hierarchical unstructured p2p networks is presented which takes into account heterogeneity of peers such as upload bandwidth, life time in the network and process capacity in its peer discovery policy as factors that influence download performance and user satisfaction. One advantage of this algorithm is that it can be performed in a completely unstructured network without imposing any change on network topology and file replication. However, it obviously decreases file download time as it is designed to discover broad-bandwidth nodes with a higher probability. This property results in a fair distribution of load over heterogeneous p2p...
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 ; Medi, A ; Sharif University of Technology
Abstract
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...
Distributed secondary control in DC microgrids with low-bandwidth communication link
, Article 7th Power Electronics, Drive Systems and Technologies Conference, PEDSTC 2016, 16 February 2016 through 18 February 2016 ; 2016 , Pages 641-645 ; 9781509003754 (ISBN) ; Blaabjerg, F ; Peyghami Akhuleh, S ; Mokhtari, H ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2016
Abstract
In this paper, a distributed secondary power sharing approach with low bandwidth communication network is proposed for low voltage direct current (LVDC) microgrids. Conventional droop control causes voltage drop in the grid and also a mismatch on the current of converters in the case of consideration of the line resistances. Proposed control system carry out the current value of the other converters to reach the accurate current sharing and suitable voltage regulation as well. Voltage and current controllers locally regulate the voltage and current of converters as a secondary controller. Secondary controller is realized locally and the communication network is only used to transfer the data...
Wideband printed slot bowtie antenna using symmetric vias
, Article Microwave and Optical Technology Letters ; Volume 58, Issue 6 , 2016 , Pages 1301-1304 ; 08952477 (ISSN) ; Amani, N ; Jafargholi, A ; Sharif University of Technology
John Wiley and Sons Inc
Abstract
This letter presents a symmetrical slot-type bowtie antenna with widened impedance bandwidth and high efficiency. Two symmetric vias are exploited underneath each slot in order to increase the antenna bandwidth up to 84% with simultaneous preservation of high efficiency (>90%), and low cross-polarization (<-10 dB). The proposed antenna is fed with 50Ω ungrounded coplanar waveguide (CPW) with no need to balun insertion and tuning stub. The proposed antenna has low profile and simple structure in comparison with previous complex wideband bowtie antennas. The commercial CST Microwave Studio software is adopted for the simulations. The antenna is fabricated and measured, while good agreement is...
A scalable framework for wireless distributed computing
, Article IEEE/ACM Transactions on Networking ; Volume 25, Issue 5 , 2017 , Pages 2643-2654 ; 10636692 (ISSN) ; Yu, Q ; Maddah Ali, M. A ; Avestimehr, A. S ; Sharif University of Technology
Abstract
We consider a wireless distributed computing system, in which multiple mobile users, connected wirelessly through an access point, collaborate to perform a computation task. In particular, users communicate with each other via the access point to exchange their locally computed intermediate computation results, which is known as data shuffling. We propose a scalable framework for this system, in which the required communication bandwidth for data shuffling does not increase with the number of users in the network. The key idea is to utilize a particular repetitive pattern of placing the data set (thus a particular repetitive pattern of intermediate computations), in order to provide the...
HB2DS: a behavior-driven high-bandwidth network mining system
, Article Journal of Systems and Software ; Volume 127 , 2017 , Pages 266-277 ; 01641212 (ISSN) ; Jalili, R ; Sharif University of Technology
Elsevier Inc
2017
Abstract
This paper proposes a behavior detection system, HB2DS, to address the behavior-detection challenges in high-bandwidth networks. In HB2DS, a summarization of network traffic is represented through some meta-events. The relationships amongst meta-events are used to mine end-user behaviors. HB2DS satisfies the main constraints exist in analyzing of high-bandwidth networks, namely online learning and outlier handling, as well as one-pass processing, delay, and memory limitations. Our evaluation indicates significant improvement in big data stream analyzing in terms of accuracy and efficiency. © 2016 Elsevier Inc
A fast online bandwidth empirical mode decomposition scheme for avoidance of the mode mixing problem
, Article Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science ; Volume 232, Issue 20 , 2018 , Pages 3652-3674 ; 09544062 (ISSN) ; Hosseini Kordkheili, S. A ; Navazi, H. M ; Sharif University of Technology
SAGE Publications Ltd
2018
Abstract
The main objective of this work is to propose a scheme to extract intrinsic mode functions of online data with an acceptable speed as well as accuracy. For this purpose, an individual block framework method is firstly employed to extract the intrinsic mode functions. In this method, buffers are selected such that they overlap with their neighbors to prevent the end effect errors with no need for the averaging process. And in order to avoid the mode mixing problem, a bandwidth empirical mode decomposition scheme is developed to effectively improve the results. Through this scheme, an auxiliary function made of both high- and low-frequency components corresponding to noise and dominant...
Gain ripple minimization in the wide-band SCISSOR raman amplifier
, Article Optics Communications ; Volume 282, Issue 8 , 2009 , Pages 1648-1653 ; 00304018 (ISSN) ; Bazouband, F ; Sharif University of Technology
2009
Abstract
A side coupled integrated spaced sequence (SCISSOR) of Silicon or Chalcogenide glass microrings of different diameter are considered as a wide-band Raman amplifier. Because the two-photon absorption (TPA) losses in Chalcogenide glass are less than that of Silicon, it is shown that Chalcogenide microrings are suitable for wide-band Raman amplifier in the telecommunication bandwidth (1.5 μm). The Lagrange unknown multiplier method is employed to minimize the gain ripple of the amplifier versus the pump and system parameters. Crown Copyright © 2008
Ferrite-based wideband circularly polarized microstrip antenna design
, Article ETRI Journal ; Volume 41, Issue 3 , 2019 , Pages 289-297 ; 12256463 (ISSN) ; Komjani, N ; Rejaei, B ; Ghalibafan, J ; Sharif University of Technology
John Wiley and Sons Inc
2019
Abstract
In this paper, a wideband, circularly polarized patch antenna is proposed that leverages the unidirectional resonant modes of a circular patch mounted on top of a grounded dielectric-ferrite substrate. The proposed antenna is fed via the proximity coupling method and several parasitically coupled patches are placed on a dielectric superstrate to enhance the impedance bandwidth of the antenna. The resonant modes of the structure rotate only in the clockwise or counter clockwise directions. In the frequency range where the effective permeability of the ferrite layer is negative, the resonance frequencies of these modes differ significantly, which produces a large axial ratio (AR) bandwidth....
Achieving subwavelength field confinement in sub-terahertz regime by periodic metallodielectric waveguides
, Article Optics Express ; Volume 27, Issue 4 , 2019 , Pages 4226-4237 ; 10944087 (ISSN) ; Ahmadi Boroujeni, M ; Abbaszadeh, A ; Sharif University of Technology
OSA - The Optical Society
2019
Abstract
In this paper, we report on a periodic metallo-dielectric structure that supports geometry-induced surface plasmons in the sub-terahertz regime. The proposed structure is made up of a dielectric-coated metallic grating sandwiched by parallel metal plates. Based on the modal analysis of 2D and 3D structures, the impact of a metal cladding and a customized dielectric coating on the dispersion relation and field distribution of the guided surface wave is investigated. It is found that modal field confinement is improved in the presence of a metal cladding without narrowing the operational bandwidth of the waveguide. Moreover, a customized subwavelength-sized dielectric coating based on...
Achieving subwavelength field confinement in sub-terahertz regime by periodic metallodielectric waveguides
, Article Optics Express ; Volume 27, Issue 4 , 2019 , Pages 4226-4237 ; 10944087 (ISSN) ; Ahmadi Boroujeni, M ; Abbaszadeh, A ; Sharif University of Technology
OSA - The Optical Society
2019
Abstract
In this paper, we report on a periodic metallo-dielectric structure that supports geometry-induced surface plasmons in the sub-terahertz regime. The proposed structure is made up of a dielectric-coated metallic grating sandwiched by parallel metal plates. Based on the modal analysis of 2D and 3D structures, the impact of a metal cladding and a customized dielectric coating on the dispersion relation and field distribution of the guided surface wave is investigated. It is found that modal field confinement is improved in the presence of a metal cladding without narrowing the operational bandwidth of the waveguide. Moreover, a customized subwavelength-sized dielectric coating based on...
On the effectiveness of the PIT in reducing upstream demand in an NDN router
, Article Performance Evaluation ; Volume 138 , 2020 ; Roberts, J ; Leonardi, E ; Movaghar, A ; Sharif University of Technology
Elsevier B.V
2020
Abstract
The paper revisits the performance evaluation of caching in a Named Data Networking (NDN) router where the content store (CS) is supplemented by a pending interest table (PIT). The PIT aggregates requests for a given content that arrive within the download delay and thus brings an additional reduction in upstream bandwidth usage beyond that due to CS hits. We extend prior work on caching with non-zero download delay (non-ZDD) by proposing a novel mathematical framework that is more easily applicable to general traffic models and by considering alternative cache insertion policies. Specifically we evaluate the use of an LRU filter to improve CS hit rate performance in this non-ZDD context. We...
Wide-band/angle blazed dual mode metallic groove gratings
, Article IEEE Transactions on Antennas and Propagation ; 16 June , 2020 ; Abbassi, M. A ; Rahmani, B ; Memarian, M ; Mehrany, K ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2020
Abstract
A simple approach to acquire wide-band/angle blazing operation in one-dimensional metallic gratings is investigated by means of mode-matching and equivalent circuit analysis. The gratings are single-groove perfectly conducting gratings that support two propagating guided modes (opposed to typical single mode cases). It is shown under what conditions, one can achieve blazing over a wide range of frequencies and angles. Most importantly, it is identified what governs blazing, in particular the true matching condition that needs to be satisfied, and how the structures’ multiple resonances play role in achieving such matching and tailoring the bandwidth. Parameters of the proposed equivalent...
Partition pruning: Parallelization-aware pruning for dense neural networks
, Article 28th Euromicro International Conference on Parallel, Distributed and Network-Based Processing, PDP 2020, 11 March 2020 through 13 March 2020 ; 2020 , Pages 307-311 ; Albaqsami, A ; Jasemi, M ; Bagherzadeh, N ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2020
Abstract
As recent neural networks are being improved to be more accurate, their model's size is exponentially growing. Thus, a huge number of parameters requires to be loaded and stored from/in memory hierarchy and computed in processors to perform training or inference phase of neural network processing. Increasing the number of parameters causes a big challenge for real-time deployment since the memory bandwidth improvement's trend cannot keep up with models' complexity growing trend. Although some operations in neural networks processing are computational intensive such as convolutional layer computing, computing dense layers face with memory bandwidth bottleneck. To address the issue, the paper...
Investigation on microwave absorption characteristics of ternary MWCNTs/CoFe2O4/FeCo nanocomposite coated with conductive PEDOT-Polyaniline Co-polymers
, Article Ceramics International ; Volume 47, Issue 9 , 2021 , Pages 12244-12251 ; 02728842 (ISSN) ; Farouk, N ; Mortezaei, N ; Yumashev, A. V ; Niaz Akhtar, M ; Arabmarkadeh, A ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
In this study, ternary MWCNTs/CoFe2O4/FeCo nanocomposite coated with conductive PEDOT-polyaniline (PA@MW/F/C) co-polymers were synthesized by microwave-assisted sol-gel followed in-situ polymerization methods. The phases, crystal structures, morphologies, magnetic and electromagnetic features of the as-prepared samples were identified via XRD, SEM, XPS, VSM, and VNA respectively. Absorption characteristics were investigated in the frequency (12–18 GHz) Ku band. XRD, VSM and SEM analysis confirmed the partial reduction process of CoFe2O4 and successfully decorated magneto-dielectric particles with co-polymers. By measuring electromagnetic features of the samples, it was found that coating...
Wide-band/angle blazed dual-mode metallic groove gratings
, Article IEEE Transactions on Antennas and Propagation ; Volume 69, Issue 1 , 2021 , Pages 379-386 ; 0018926X (ISSN) ; Abbassi, M. A ; Rahmani, B ; Memarian, M ; Mehrany, K ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2021
Abstract
A simple approach to acquire wide-band/angle blazing operation in 1-D metallic gratings is investigated by means of mode-matching and equivalent circuit analysis. The gratings are single-groove perfectly conducting gratings that support two propagating guided modes (opposed to typical single-mode cases). It is shown under what conditions one can achieve blazing over a wide range of frequencies and angles. Most importantly, it is identified what governs blazing, in particular the true matching condition that needs to be satisfied, and how the structures' multiple resonances play role in achieving such matching and tailoring the bandwidth. Parameters of the proposed equivalent circuit model...