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Computing accurate performance bounds for best effort networks-on-chip
, Article IEEE Transactions on Computers ; Vol. 62, issue. 3, Article number 6109240 , 2013 , pp. 452-467 ; ISSN: 00189340 ; Murali, S ; Benini, L ; Angiolini, F ; De Micheli, G ; Sarbazi-Azad, H ; Sharif University of Technology
Abstract
Real-time (RT) communication support is a critical requirement for many complex embedded applications which are currently targeted to Network-on-chip (NoC) platforms. In this paper, we present novel methods to efficiently calculate worst case bandwidth and latency bounds for RT traffic streams on wormhole-switched NoCs with arbitrary topology. The proposed methods apply to best-effort NoC architectures, with no extra hardware dedicated to RT traffic support. By applying our methods to several realistic NoC designs, we show substantial improvements (more than 30 percent in bandwidth and 50 percent in latency, on average) in bound tightness with respect to existing approaches
The triangular pyramid: Routing and topological properties
, Article Information Sciences ; Vol. 180, issue. 11 , 2010 , p. 2328-2339 ; ISSN: 00200255 ; Sarbazi-Azad, H ; Sharif University of Technology
Abstract
In this paper, a new topology for multicomputer interconnection networks, based on triangular mesh, is proposed. The new network, referred to as the triangular pyramid (or tripy for short), has L levels of triangular mesh. We study some basic important properties of the proposed network as well as introduce a routing algorithm for the tripy network based on the routing of triangular meshes. We prove that this form of pyramidal network is Hamiltonian, Hamiltonian-connected, and pancyclic. We also prove that the proposed network is 6-colorable and conduct a brief comparison of the tripy and its traditional pyramid counterpart. Our results show that the proposed network has higher scalability,...
Unilateralization of MMIC distributed amplifiers
, Article IEEE Transactions on Microwave Theory and Techniques ; Vol. 62, issue. 12 , 2014 , pp. 3041-3052 ; ISSN: 00189480 ; Medi, A ; Sharif University of Technology
Abstract
This paper presents an unilateralization technique for distributed amplifiers (DAs) based on the transformer coupling between the gate and drain lines. Theoretical analysis of the DA indicates that the voltage waves in the gate and drain lines can be described by a system of linear partial differential equations. The transformer coupling between the lines allows for cancellation of the reverse transmission coefficient of the system. There is an optimal value for the coupling coefficient between the lines that unilateralizes the DA. This optimal coupling coefficient is derived in terms of the gate-drain capacitance and capacitances of the gate and drain lines. Using the proposed technique,...
Raman random laser in one-dimensional system
, Article Journal of the Optical Society of America B: Optical Physics ; Vol. 31, Issue. 6 , 2014 , Pages 1308-1315 ; ISSN: 07403224 ; Shojaie, E ; Sani, M ; Sharif University of Technology
Abstract
The probability of occurrence of random cavities' resonance frequency in the Stokes bandwidth of the Raman active medium can cause Raman laser oscillation in the random structures. Due to the small bandwidth of Raman line shape, the probability of the simultaneous appearance of random cavity resonance frequencies in the cascade Stokes line shapes is small. As a result, the cascade Raman laser oscillation effects on the saturation behavior are negligible. The nonlinear transmission matrix method is employed to determine the statistical behavior of a Raman random laser. Our results showed that the statistical behavior depends on the position of the Stokes line shape relative to the center of...
Minimum power Miller-compensated CMOS operational amplifiers
, Article Scientia Iranica ; Vol. 21, Issue. 6 , 2014 , pp. 2243-2249 ; e-ISSN :23453605 ; Bakhtiar, M. S ; Sharif University of Technology
Abstract
A new approach for the design of two-stage Miller-compensated CMOS op amps is presented. The paper studies the basic relations between power consumption, unitygain bandwidth, the biasing region, technology parameters, and the external capacitive load. As a result, simple and efficient design guides are provided to achieve the minimum possible power consumption for the given specifications and for short-channel devices. It is shown that the conventional design procedures do not always result in minimum power op amps. The presented results are also verified by Spectre simulations
Comparison between optimal interconnection network in different 2D and 3D NoC structures
, Article International System on Chip Conference ; 2014 , p. 171-176 ; Zabihi, M ; Sarvari, R ; Sharif University of Technology
Abstract
The current article studies optimal intercore interconnect network in a NoC structure for 2D and 3D mesh, torus and hypercube topologies. Optimal wire width/spacing is calculated by numerically maximizing bandwidth times the reciprocal delay, which depends on the technology node and hop length. Through 3D integration and increasing tiers, optimal interconnect width and spacing in torus and hypercube topologies will decrease. The core-to-core channel width in all topologies will be obtained by assigning 20% of the power consumption to the routers. By increasing number of cores, channel width will decrease due to reduced power consumption of each core. This is more in hypercube topology, due...
A novel design methodology for low-noise and high-gain transimpedance amplifiers
, Article Proceedings of the 2014 Argentine School of Micro-Nanoelectronics, Technology and Applications, EAMTA 2014 ; 2014 , pp. 77-82 ; ISBN: 9789871907861 ; Medi, A ; Bozorgzadeh, B ; Saniei, N ; Sharif University of Technology
Abstract
This paper reports on design and measurement results of a state of the art low-noise and high-gain transimpedance amplifier (TIA) implemented in 0.18 μm TSMC CMOS technology. Thorough design methodology for high gain and low power TIA design for 2.5 Gb/s optical communication circuits family is presented. A noiseless capacitive feedback is proposed and implemented as a noise efficient feedback network for TIA circuits. Besides, analytical noise calculations in this family of TIA circuits are presented and optimum noise criteria are derived. The saturation and instability problem of TIA circuits resulted from DC dark current of the input photodiodes (PDs) is addressed and a circuit level...
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...
A 90 nm-CMOS IR-UWB BPSK transmitter with spectrum tunability to improve peaceful UWB-narrowband coexistence
, Article IEEE Transactions on Circuits and Systems I: Regular Papers ; Vol. 61, issue. 6 , January , 2014 , p. 1836-1848 ; 15498328 ; Fotowat-Ahmady, A ; Nezhad, A. Z ; Serdijn, W. A ; Sharif University of Technology
Abstract
A new ultra wideband (UWB) pulse generator covering a-10 dB bandwidth of 2.4-4.6 GHz with a tunable center frequency of 5-5.6 GHz to mitigate coexistence issues of impulse radio UWB (IR-UWB) systems and IEEE802.11.a WLAN or other narrowband (NB) systems in 90 nm-CMOS technology is proposed. The UWB pulse is generated based on frequency up-conversion of the first derivative of the Gaussian pulse, which creates an adjustable null in the frequency spectrum. Simulation results show that employing the proposed pulse generator mitigates the mutual interference between UWB and WLAN systems, significantly. The proposed transmitter consists of a low frequency signal generator, an LC oscillator and a...
Sending a laplacian source using hybrid digital-analog codes
, Article IEEE Transactions on Communications ; Vol. 62, issue. 7 , 2014 , p. 2544-2557 ; Aghagolzadeh, A ; Behroozi, H ; Sharif University of Technology
Abstract
In this paper, we study transmission of a memoryless Laplacian source over three types of channels: additive white Laplacian noise (AWLN), additive white Gaussian noise (AWGN), and slow flat-fading Rayleigh channels under both bandwidth compression and bandwidth expansion. For this purpose, we analyze two well-known hybrid digital-analog (HDA) joint source-channel coding schemes for bandwidth compression and one for bandwidth expansion. Then we obtain achievable (absolute-error) distortion regions of the HDA schemes for the matched signal-to-noise ratio (SNR) case as well as the mismatched SNR scenario. Using numerical examples, it is shown that these schemes can achieve a distortion very...
Speed control of servo drives with a flexible couplings using fractional order state feedback
, Article PEDSTC 2014 - 5th Annual International Power Electronics, Drive Systems and Technologies Conference ; 2014 , p. 25-30 ; Moghadam, B. E ; Sharif University of Technology
Abstract
Using elastic couplings in servo motor drives may lead to torsional oscillations which are usually extinguished by reducing the bandwidth of the control system as a countermeasure. A high performance servo drive however needs fast dynamic characteristics. The conventional controllers, such as PI controllers, may not be able to improve the dynamic response while keeping the system stable. Fractional order modeling offers a good framework for flexible structures such as two mass servo drives. In this paper, the dynamic response and stability of two-mass servo drive is improved using a fractional order controller. The fractional order controller allows increasing the phase margin of the system...
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...
Simulation of deep level traps effects in quantum well transistor laser
, Article Journal of Computational Electronics ; Volume 12, Issue 4 , August , 2013 , Pages 812-815 ; 15698025 (ISSN) ; Faez, R ; Sharif University of Technology
2013
Abstract
In this paper, we present an analytical model to analyze the influence of deep level traps on the static and dynamic responses of transistor laser (TL). Our analyze is based on analytically solving the continuity equation and rate equations including the effect of the deep level trap (DLT), which incorporate the virtual states as a conversion mechanism. The results of simulation show that the main characteristics of laser such as threshold current, quantum efficiency, output power, and modulation bandwidth are affected by total density of traps in the active region
On the gaussian characteristics of aggregated short-lived flows on high-bandwidth links
, Article Proceedings - 27th International Conference on Advanced Information Networking and Applications Workshops ; 2013 , Pages 860-865 ; 9780769549521 (ISBN) ; Jahangir, A. H ; Sharif University of Technology
2013
Abstract
Traffic modeling, traffic decomposition, and traffic engineering are some of the applications of traffic characterization that are mainly based on statistical characteristics of the network traffic. Many empirical analyses on Internet traffic traces show that the flow inter-arrival time distribution generally follows the Weibull distribution. As the scale of the network becomes larger, the Weibull distribution degrades to the Poisson distribution and when the flow arrival rate is high, it asymptotically converges to the Normal distribution. The aggregated traffic on high bandwidth links is the result of statistical multiplexing of many traffic sources, and the flow arrival rate on these...
Analysis of deep level trap effects in transistor lasers
, Article Lasers in Engineering ; Volume 25, Issue 5-6 , 2013 , Pages 313-322 ; 08981507 (ISSN) ; Mirmoeini, S ; Faez, R ; Sharif University of Technology
2013
Abstract
In this paper we present an analytical model to analyze the influence of deep level traps on the static and dynamic responses of transistor laser (TL). Our analysis is based on analytically solving the continuity equation and rate equations including the effect of the deep level trap (DLT), which incorporates the virtual states as a conversion mechanism. The results of simulation show that the main characteristics of laser such as threshold current, quantum efficiency, output power, and modulation bandwidth are affected by total density of traps in the active region
Power allocation and performance analysis for incremental-selective decode-and-forward cooperative communications over Nakagami-m fading channels
, Article IEICE Transactions on Communications ; Volume E96-B, Issue 6 , 2013 , Pages 1531-1539 ; 09168516 (ISSN) ; Saadat, R ; Aref, M. R ; Sharif University of Technology
2013
Abstract
The focus of this study is the performance of the relaying network with incremental selective decode-and-forward (ISDF) protocol in non-selective slow Nakagami-m fading channels. To enhance bandwidth efficiency, when the direct transmission is not successful the relay is used to retransmit a clean copy of the source signal. The proposed protocol achieves a significant reduction in the power consumption and an improvement in performance compared to the fixed decode-and-forward (DF). The exact symbol error rate (SER) of M-PSK modulation for the ISDF protocol over general fading channels is derived. However, as the exact SER analysis is very complicated, we provide an approximated SER...
Compact broadband printed monopole antenna
, Article Applied Computational Electromagnetics Society Journal ; Volume 28, Issue 4 , 2013 , Pages 321-326 ; 10544887 (ISSN) ; Jafargholi, A ; Sharif University of Technology
2013
Abstract
A compact printed monopole antenna for broadband application is presented. The proposed antenna, having a total physical size of 21 × 6.5 mm consists of a patch fed by a coaxial line and an SMA connector as partial finite ground plane. The modified patch plane with a slot in its feed point helps to increase the impedance bandwidth of the proposed antenna. The optimal design may offer an ultra-wide impedance bandwidth from 2.56 GHz to 20 GHz. A prototype is fabricated and tested. The agreement between the simulated and measured results is quite good
A 4-Bit, 1.6 GS/s low power flash ADC, based on offset calibration and segmentation
, Article IEEE Transactions on Circuits and Systems I: Regular Papers ; Volume 60, Issue 9 , 2013 , Pages 2285-2297 ; 15498328 (ISSN) ; Sharifkhani, M ; Sadughi, S ; Sharif University of Technology
2013
Abstract
A low power 4-bit, 1.6 GS/s flash ADC is presented. A new power reduction technique which masks the unused blocks in a semi-pipeline chain of latches and encoders is introduced. The proposed circuit determines the unused blocks based on a pre-sensing of the signal. Moreover, a reference voltage generator with very low static power dissipation is used. Novel techniques to reduce the sensitivity to dynamic noise are proposed to suppress the noise effects on the reference generator. The proposed circuit reduces the power consumption by 20 percent compared to the conventional structure when a Nyquist rate OFDM signal is applied. The INL and DNL of the converter are smaller than 0.3 LSB after...
Broadband miniaturized efficient array antennas
, Article Applied Computational Electromagnetics Society Journal ; Volume 28, Issue 3 , 2013 , Pages 188-194 ; 10544887 (ISSN) ; Jafargholi, A ; Sharif University of Technology
2013
Abstract
This paper introduces a new array architecture, in which antenna elements are arranged in a spiral curve. The spiral array enhances ultra-wideband (UWB) pattern characteristics compared to alternative array geometries of similar elements, without requiring a complex feed network for frequency change compensation. A number of examples are illustrated to demonstrate the array capability in broadband array designs. It is revealed that for the same number of elements and curvature lengths, a spiral array has a wider radiation bandwidth than the corresponding circular and linear array antennas. In addition, it is also demonstrated that the spiral architecture discussed here can be best suited for...
Computing accurate performance bounds for best effort networks-on-chip
, Article IEEE Transactions on Computers ; Volume 62, Issue 3 , 2013 , Pages 452-467 ; 00189340 (ISSN) ; Murali, S ; Benini, L ; Angiolini, F ; De Micheli, G ; Sarbazi Azad, H ; Sharif University of Technology
2013
Abstract
Real-time (RT) communication support is a critical requirement for many complex embedded applications which are currently targeted to Network-on-chip (NoC) platforms. In this paper, we present novel methods to efficiently calculate worst case bandwidth and latency bounds for RT traffic streams on wormhole-switched NoCs with arbitrary topology. The proposed methods apply to best-effort NoC architectures, with no extra hardware dedicated to RT traffic support. By applying our methods to several realistic NoC designs, we show substantial improvements (more than 30 percent in bandwidth and 50 percent in latency, on average) in bound tightness with respect to existing approaches