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khorami--hamed
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Study, Research and Diagnosing of Oil and Gas Production Supply by Application of a System Dynamic Approach with Concentration on Supply Chain Collaboration
, M.Sc. Thesis Sharif University of Technology ; Fatahi, Omid (Supervisor) ; Khorami, Hamed ($item.subfieldsMap.e)
Abstract
In today’s competitive market, organizations need to modify their local perspective on enterprise, to a wider scope including supply chain. Focusing on supply chain, helps a more effective and efficient management for organizations. Today’s supply chain management is an inevitable part of enterprise management for achievement of integration between a supply chain’s partners. Oil and gas supply chain, as a complex supply chain, needs an effective and efficient management which uses from different tools and techniques, diagnoses the related errors and drawbacks among upstream partners. A management with such characteristics is scarce, and in this thesis it is tried to present an effective and...
One-dimensional adiabatic circuits with inherent charge recycling
, Article Electronics Letters ; Volume 51, Issue 14 , July , 2015 , Pages 1056-1058 ; 00135194 (ISSN) ; Sharifkhani, M ; Sharif University of Technology
Institution of Engineering and Technology
2015
Abstract
A new switching method for the stabilisation of a one-dimensional capacitor array tank for the stepwise charging of a load capacitor is presented. In this method, the tank capacitor configuration is rearranged in a circular manner once the charging process of a load capacitor finishes and before the charging process of a new load capacitor begins. Unlike previously reported methods, this method does not require backward switching for the stabilisation of tank capacitor voltages. Hence, the proposed method reduces the number of charging process steps by a factor of up to 2 compared with the conventional method. Moreover, since the tank recycles its charge inherently, the capacitive load can...
Zero-power mismatch-independent digital to analog converter
, Article AEU - International Journal of Electronics and Communications ; Volume 69, Issue 11 , 2015 , Pages 1599-1605 ; 14348411 (ISSN) ; Sharifkhani, M ; Sharif University of Technology
Elsevier GmbH
2015
Abstract
A new switched-capacitor digital to analog converter (DAC) is presented. In this DAC, a ladder of series capacitors is used to generate the output voltage levels. A correction phase is used to increase the precision of the DAC. It is analytically shown that the proposed DAC is mismatch independent by virtue of the correction phase. That is after few correction phases (typically one), the effect of mismatch on the reference voltage levels on the ladder diminishes and an accurate voltage division is provided. It is proven that the whole process sinks no extra charge from the power supply. Furthermore, post layout simulations in 0.18 μm technology proves the benefits of the proposed method
Elimination of the effect of bottom-plate capacitors in C-2C DAC using a layout technique
, Article Microelectronics Journal ; Volume 46, Issue 12 , 2015 , Pages 1275-1282 ; 00262692 (ISSN) ; Sharifkhani, M ; Sharif University of Technology
2015
Abstract
An efficient layout technique is proposed to eliminate the effect of the bottom-plate capacitors in a C-2C Digital to Analog Converter (DAC). Using this technique, the bottom-plate capacitors of 2C capacitors in the C-2C structure are placed in parallel with 1C capacitors. Then, the effect of the bottom plate capacitors is nulled by modifying the size of the main 1C capacitors. Hence, avoiding the complexity of calibration, this technique can preclude the effect of the bottom-plate to ground capacitance. Statistical simulations prove that the proposed technique is robust to non-ideal effects such as mismatch or parasitic capacitors. A 10-bit C-2C DAC is modeled in COMSOL Multiphysics using...
High-speed low-power comparator for analog to digital converters
, Article AEU - International Journal of Electronics and Communications ; Volume 70, Issue 7 , 2016 , Pages 886-894 ; 14348411 (ISSN) ; Sharifkhani, M ; Sharif University of Technology
Elsevier GmbH
2016
Abstract
A low-power high-speed two-stage dynamic comparator is presented. In this circuit, the voltage swing of the first stage of the comparator, pre-amplifier stage, is limited to Vdd/2 in order to reduce the first stage power consumption. Also, this voltage swing limitation provides a strong drive at the evaluation phase for the second stage to enhance the comparison speed. Analytical derivations along with post layout simulation results prove that the proposed method speeds up the conventional circuit by a factor of two in the same budget of power consumption and offset voltage. Furthermore, the proposed circuit offers a wide input common mode range as large as the supply voltage while employing...
Low-power technique for dynamic comparators
, Article Electronics Letters ; Volume 52, Issue 7 , 2016 , Pages 509-511 ; 00135194 (ISSN) ; Sharifkhani, M ; Sharif University of Technology
Institution of Engineering and Technology
2016
Abstract
A low-power technique to reduce the power consumption of the dynamic comparators is presented. Using this technique, the pre-ampli-fication phase of the comparator is stopped without any effect on the dynamic behaviour of the comparator. Therefore, the power consumption of the pre-amplifier stage which is the main part of the total power consumption is reduced significantly. Simulation results in various comparators reveal that the proposed technique reduces the total power consumption by more than 50%
An efficient fast switching procedure for stepwise capacitor chargers
, Article IEEE Transactions on Very Large Scale Integration (VLSI) Systems ; Volume PP, Issue 99 , 2016 ; 10638210 (ISSN) ; Sharifkhani, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2016
Abstract
A new low-power switching procedure for stepwise capacitor chargers is presented. In this procedure, a novel displacement method is utilized to improve the speed by a factor of two while preserving energy efficiency. Moreover, the load capacitor retains its charge after the charging process finishes and permits the circuit charge another predischarged load capacitor without an efficiency degradation problem (instability). Also, the control circuit of the switching procedure is implemented using only flip-flops with no combinational logic, therefore, it systematically prevents glitch power dissipation and improves the efficiency. Analytical derivations are proposed to model the switching...
General Characterization Method and a Fast Load-Charge-Preserving Switching Procedure for the Stepwise Adiabatic Circuits
, Article IEEE Transactions on Circuits and Systems I: Regular Papers ; Volume 63, Issue 1 , 2016 , Pages 80-90 ; 15498328 (ISSN) ; Sharifkhani, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2016
Abstract
An analytical method is presented to characterize stepwise adiabatic circuits (SACs). In this method, the SACs are modeled as a discrete time system. Unlike previous methods, the stability is verified for arbitrary load capacitor ratios. Moreover, this method presents analytical derivations to offer an area/energy efficient design methodology. MATLAB simulations, post-layout simulations in the CMOS 0.18 μm technology, silicon measurements, and measurements based on discrete components confirm the precision of the analytical derivations. Using the proposed design methodology, a capacitive tank has been designed which reduces the energy consumption by 20% while the total size of the tank...
A high-speed method of dynamic comparators for sar analog to digital converters
, Article 59th IEEE International Midwest Symposium on Circuits and Systems, MWSCAS 2016, 16 October 2016 through 19 October 2016 ; 2017 ; 15483746 (ISSN); 9781509009169 (ISBN) ; Sharifkhani, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2017
Abstract
A low-power high-speed two-stage dynamic comparator is presented. The voltage fluctuation at the first stage of the comparator (pre-Amplifier stage) is limited to V dd=2. Therefore, the power consumption of the first stage which is the dominant part of the total power consumption is reduced. The output voltage of the first stage is kept above V dd=2. As a result, during the comparison the second stage of the comparator (latch) is activated stronger compared to the conventional comparator. To prove the benefits of the proposed comparator, the proposed and the other circuits are simulated in the equal budget of power and offset. Simulation results prove that the proposed comparator is faster...
Excess power elimination in high-resolution dynamic comparators
, Article Microelectronics Journal ; Volume 64 , 2017 , Pages 45-52 ; 00262692 (ISSN) ; Sharifkhani, M ; Sharif University of Technology
Elsevier Ltd
2017
Abstract
In this paper, a method is presented to reduce the power consumption of the two-stage dynamic comparators. In the two-stage dynamic comparators, the first stage (pre-amplifier stage) amplifies the input differential voltage. Then the second stage (latch stage) is activated and finishes the comparison. When the comparison is about to finish, the balance of the positive feedback of the latch stage tends to tilt toward one of the outputs; after this, to the end of the comparison, there is no need for additional pre-amplification gain which causes excess power consumption. In this paper, a method is proposed to eliminate this part of power consumption. It is shown that while reducing the power...
A low-power technique for high-resolution dynamic comparators
, Article International Journal of Circuit Theory and Applications ; Volume 46, Issue 10 , 2018 , Pages 1777-1795 ; 00989886 (ISSN) ; Sharifkhani, M ; Sharif University of Technology
John Wiley and Sons Ltd
2018
Abstract
A low-power technique for high-resolution comparators is introduced. In this technique, p-type metal-oxide-semiconductor field-effect transistors are employed as the input of the latch of the comparator just like the input of the preamplifier. The latch and preamplifier stages are activated in a special pattern using an inverter-based controller. Unlike the conventional comparator, the preamplification delay can be set to an optimum low value even if after the preamplification, the output voltages is less than n-channel metal-oxide semiconductor voltage threshold. As a result, the proposed comparator reduces the power consumption significantly and enhances the speed. The speed and power...
A low-power high-speed comparator for precise applications
, Article IEEE Transactions on Very Large Scale Integration (VLSI) Systems ; Volume 26, Issue 10 , 2018 , Pages 2038-2049 ; 10638210 (ISSN) ; Sharifkhani, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2018
Abstract
A low-power comparator is presented. pMOS transistors are used at the input of the preamplifier of the comparator as well as the latch stage. Both stages are controlled by a special local clock generator. At the evaluation phase, the latch is activated with a delay to achieve enough preamplification gain and avoid excess power consumption. Meanwhile, small cross-coupled transistors increase the preamplifier gain and decrease the input common mode of the latch to strongly turn on the pMOS transistors (at the latch input) and reduce the delay. Unlike the conventional comparator, the proposed structure let us set the optimum delay for preamplification and avoid excess power consumption. The...
Energy consumption analysis of the stepwise adiabatic circuits
, Article Microelectronics Journal ; Volume 104 , October , 2020 ; Saeidi, R ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
In this paper, an analytic model of the energy consumption of the Stepwise Adiabatic Circuits (SAC) when it is possible to discharge the load capacitor is proposed. Using this model, analytical derivations are calculated which shows us the power saving of the SACs. Using analytical derivations, the sizing of a capacitor tank is determined for a desired energy saving. For example, the derivations predict that if the sizing of the 3-step series tank capacitors is equal to the load capacitor, the power saving is 55%. Also, if the sizing of the tank is very large the energy saving of a 3-step stepwise charging is equal to 66.7%. Several Simulations in 0.18μm CMOS technology prove the accuracy of...
An efficient fast switching procedure for stepwise capacitor chargers
, Article IEEE Transactions on Very Large Scale Integration (VLSI) Systems ; Volume 25, Issue 2 , 2017 , Pages 705-713 ; 10638210 (ISSN) ; Sharifkhani, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2017
Abstract
A new low-power switching procedure for stepwise capacitor chargers is presented. In this procedure, a novel displacement method is utilized to improve the speed by a factor of two while preserving energy efficiency. Moreover, the load capacitor retains its charge after the charging process finishes and permits the circuit charge another predischarged load capacitor without an efficiency degradation problem (instability). Also, the control circuit of the switching procedure is implemented using only flip-flops with no combinational logic, therefore, it systematically prevents glitch power dissipation and improves the efficiency. Analytical derivations are proposed to model the switching...
An ultra low-power digital to analog converter for SAR ADCs
, Article Proceedings of the International Conference on Microelectronics, ICM, 10 December 2017 through 13 December 2017 ; Volume 2017-December , 2018 , Pages 1-4 ; 9781538640494 (ISBN) ; Sharifkhani, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2018
Abstract
A new structure of Capacitive Digital to Analog Converters (CDAC) for SAR ADCs is presented. In this structure, a number of capacitors are used in different series configurations to generate desirable voltage levels based on an input binary code. the proposed CDAC consumes a certain amount of power regardless of the input code. This method achieves more than 99.9% power reduction and 98.9% area reduction compared to the conventional binary weighted CDAC. © 2017 IEEE
Experimental Study of the Effects of Compaction Water Content on Dynamic Properties of Babolsar Sand under Anisotropic Loading
, M.Sc. Thesis Sharif University of Technology ; Jafarzadeh, Fardin (Supervisor)
Abstract
In many of the geotechnical engineering projects, such as construction of embankments and roads, soil is compacted with different water contents. Difference in compaction water content leads to different dynamic behaviors under cyclic loadings like earthquake and traffic. On the other hand, the magnitude and the direction of principal stresses on soil element, affect the dynamic response of the soil. The main objective of this research is to study the effects of compaction water content on dynamic properties of soil in anisotropic loading conditions. Therefore, the dynamic parameters of Babolsar sand, including shear strain amplitude, shear modulus and damping ratio under induced anisotropic...
Efficient Circuit and Systematic Design of Successive Approximation Register Analog to Digital Converters
, Ph.D. Dissertation Sharif University of Technology ; Sharifkhani, Mohammad (Supervisor)
Abstract
Successive Approximation Register (SAR) Analog to Digital Converter (ADC) converts an analog signal to a digital code based on binary search. In contrast to other converters, such as Pipeline and Flash ADCs, most of the SAR ADC components are digital, hence, SAR ADC is technology scalable. Therefore, designed using smaller tehcnologies, SAR ADCs are able to operate at a higher frequency with a lower power consumption and area. The main focus of this thesis is to reduce power consumption, although the proposed techniques and circuits are able to improve other features such as precision, area, or speed.Considering Digital to Analog Converter (DAC), a low-power structure and a novel method to...
An ultra low-power DAC with fixed output common mode voltage
, Article AEU - International Journal of Electronics and Communications ; Volume 96 , 2018 , Pages 279-293 ; 14348411 (ISSN) ; Saeidi, R ; Sharifkhani, M ; Sharif University of Technology
Elsevier GmbH
2018
Abstract
A novel structure of Capacitive Digital to Analog Converters (CDAC) for Successive Approximation Register Analog to Digital Converters (SAR ADC) is presented. In this CDAC, a number of pre-charged capacitors are placed in different series configurations to produce a desired voltage level. Therefore, given an input code, a series configuration of the capacitors is created to produce a voltage. Current is drawn from the supply voltage only in one step of the ADC conversion to reduce the power consumption. Therefore, the proposed CDAC consumes a fixed and small amount of power regardless of the input code. The output common mode voltage (Vcm) of the DAC remains fixed for all the digital codes....
A low-power low-offset charge-sharing technique for double-tail comparators
, Article Microelectronics Journal ; Volume 102 , August , 2020 ; Saeidi, R ; Sachdev, M ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
A charge sharing technique for high-speed double-tail comparators is presented. This technique is applied to the pre-amplifier stage of the dynamic comparators so that the maximum differential gain is applied to the latch during the latching process reducing the input referred offset voltage. In dynamic comparators a large portion of the input referred offset voltage is coming from the latch, and the proposed technique is introduced to alleviate this issue. Monte- Carlo simulations show that the proposed technique reduces the offset voltage from 16 mV to 8 mV. Due to the charge sharing technique, the pre-amplifier draws just enough power for its operation reducing the average power by 40%...
Design of low power comparator-reduced hybrid ADC
, Article Microelectronics Journal ; Volume 79 , 2018 , Pages 79-90 ; 00262692 (ISSN) ; Hajsadeghi, K ; Khorami, A ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
This paper presents a new low-power comparator-reduced hybrid ADC. The proposed ADC uses dynamic comparators to perform a high-speed low-power conversion. In order to reduce the offset and kickback noise effect of conventional dynamic comparators, a new low-kickback noise comparator with a high pre-amplifier gain is presented. Two 4bit and 8bit ADCs are designed and simulated in 0.18 μm CMOS technology with 1.8 v supply voltage. INL and DNL of 4bit ADC are less than 0.4LSB and 0.5LSB, respectively, while 8bit ADC obtains DNL and INL of 0.83LSB and 1.3LSB, respectively. With ENOB of 3.6bit and 7.2bit for 4bit and 8bit ADCs, the 4bit ADC consumes only 1.7 mW at the sampling rate of 400 Ms/s...