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A 10-W X-band class-F high-power amplifier in a 0.25-μm GaAs pHEMT technology
, Article IEEE Transactions on Microwave Theory and Techniques ; Volume 69, Issue 1 , 2021 , Pages 157-169 ; 00189480 (ISSN) ; Yaghoobi, M ; Meghdadi, M ; Medi, A ; Kiaei, S ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2021
Abstract
In this article, a design methodology is presented to realize integrated class-F high-power amplifiers (HPAs). A harmonic-control network (HCN) is proposed to present short- and open-circuit impedances to each transistor employed in the output stage of the HPA at {2}f {0} and {3}f {0} frequencies. The HCN absorbs the parasitic capacitance of the transistor and lends itself to be absorbed in the matching and power combiner networks, reducing the die area of the HPA. A proof-of-concept 9.7-10.3-GHz class-F HPA was designed and implemented in a 0.25- μ ext{m} GaAs pHEMT technology with V {DD} of 6 V. The designed HPA consists of two amplifying stages, and its output stage includes 16...
Effect of electrodeposition time on the super-capacitive performance of electrodeposited MnO2 on g-C3N4 nanosheets
, Article Journal of Alloys and Compounds ; Volume 904 , 2022 ; 09258388 (ISSN) ; Bahiraei, H ; Ghasemi, S ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
Herein, the effect of electrodeposition time on the super-capacitive performance of three-dimensional (3D) MnO2/g-C3N4 heterostructured electrodes was investigated. MnO2 nanoparticles were electrodeposited on the g-C3N4 nanosheets drop-casted on the Ni foam substrate. The microstructural analysis, carried out by FE-SEM and TEM, confirmed the homogeneous distribution of MnO2 nanoparticles on g-C3N4 nano-sheet layers. The electrochemical capacitive performances of the MnO2/g-C3N4 electrodes were evaluated by cyclic voltammetry (CV), galvanostatic charge/discharge tests, and electrochemical impedance spectra (EIS). The obtained results suggested that the supercapacitor (SC) performance of all...
Design of Oscillator with Active Inductor and Investigation of Noise Cancellation in Oscillators
, M.Sc. Thesis Sharif University of Technology ; Sharif Bakhtiar, Mehrdad (Supervisor)
Abstract
In this thesis, at first, we study the active inductors have been reported in the literature. Then by choosing one of them and investigating its advantages and disadvantages, we changed the structure in a way to solve its problems. On the way by using this active inductor and a negative capacitor, we designed an oscillator in 1.5 GHz frequency that has -106 dBc/Hz phase noise at 1MHz offset and its FOM value is 160 dBc. Also this oscillator is capable of frequency tunability of oscillation from 500 MHz to 2.2 GHz. In this spectrum the phase noise is changing between -100 dBc/Hz and -110 dBc/Hz. In the second part, in the aim of improvement of phase noise of oscillator structures based on...
Capacitive Sensors for user Gesture Recognition in Smart Environments
, M.Sc. Thesis Sharif University of Technology ; Karbalaee Aghajan, Hamid (Supervisor)
Abstract
To create applications for smart environments we can select from a huge variety of sensors that measure environmental parameters within the premises. Capacitive proximity sensors use weak electric fields to recognize conductive objects, such as the human body. They can be unobtrusively applied or even provide information when hidden from view which make these sensor more popular. Furthermore, these sensors are low cost, precise and low power. In this thesis, we study the construction and operation of capacitive sensors and the challenges of using them. Then we use them to produce smart devices. Smart flooring is used on the ground and it can be used to track people or fall detection. Smart...
Investigation of Water Electrical Parameters as a Function of Measurement Frequency and Concentration Using Cylindrical Capacitive Sensors
, M.Sc. Thesis Sharif University of Technology ; Golnabi, Hossein (Supervisor) ; Gobal, Fereydoon (Co-Advisor)
Abstract
The electrical conductivity of the solution has been one of the important physical quantities in many application. In this respect many probes and devices such as conductive sensors have been devised. In this study electrical properties of different water samples at frequency step range of 100-100000 Hz are measured by using the long cylindrical capacitive sensor and a measuring module (LCR-703). Operation of the capacitance measurement module for such probes is based on the auto balancing bridge method. Comparison of the measured capacitances and measured resistances for different water samples shows a decrease by increasing the measurement frequency. In another study the dielectric...
Obtaining the Frequency Response of Voltage Transformers
, M.Sc. Thesis Sharif University of Technology ; Mokhtari, Hossein (Supervisor)
Abstract
In this thesis a new method to determine the accuracy of CVT in measuring harmonics has been proposed. Capacitive voltage transformers are known as an important tool in measuring the harmonics. However, the frequency response of CVT contains cut-off and pass characteristics, because of the resonances of the internal elements. One of the main problems is in determining the frequency response of HV voltage source capable of accurate change to apply to CVT. The proposed method reduces the voltage level of the HV source. Also, the source structure and the effect of the additional elements are described and the accuracy of the method has been evaluated by simulation and experimental results
A 1.8-V high-speed 13-bit pipelined analog to digital converter for digital IF applications
, Article Proceedings of the 2003 IEEE International Symposium on Circuits and Systems, Bangkok, 25 May 2003 through 28 May 2003 ; Volume 1 , 2003 , Pages I885-I888 ; 02714310 (ISSN) ; Mehrmanesh, S ; Vahidfar, M. B ; Atarodi, M ; Sharif University of Technology
2003
Abstract
A 1.8-v 13-bit 25MS/S pipelined analog-to-digital (A/D) converter was designed and simulated using 0.18um CMOS technology. The proposed new high speed low power class AB opamp makes it possible to achieve requirements of 13-bit resolution and settling in 12ns within 0.01% accuracy. An optimum architecture for noise and power consideration is also selected to reduce power. Total Power dissipation is about 82 mw from a single 1.8 v supply, where INL and DNL are 0.7 LSB and 0.6 LSB respectively. SNDR of 75.5 dB is achieved
A low power 25 MS/S 12-bit pipelined analog to digital converter for wireless applications
, Article 2003 Southwest Symposium on Mixed-Signal Design, SSMSD 2003, 23 February 2003 through 25 February 2003 ; 2003 , Pages 38-42 ; 0780377788 (ISBN); 9780780377783 (ISBN) ; Mehrmanesh, S ; Vahidfar, M. B ; Safarian, A. Q ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2003
Abstract
A 12 bit 25 MS/S pipelined analog-to-digital (A/D) converter was designed and simulated using 0.35 μm CMOS technology. The proposed new high speed class AB opamp makes it possible to achieve requirements of 12 bit resolution and settling in 20 ns within 0.05% accuracy. However, pipeline ADCs are tolerant to comparator's offset, but using dynamic comparators, power dissipation can be reduced. So a dynamic comparator is designed which is more power efficient. Total power dissipation is about 76 mW from a single 3 V supply, where INL and DNL are 0.8 LSB and 0.6 LSB respectively. A SNDR of 70.1 dB is achieved. © 2003 IEEE
Electrochemical synthesis of reduced graphene oxide/TiO2 nanotubes/Ti for high-performance supercapacitors
, Article Ionics ; Volume 21, Issue 2 , 2014 , Pages 525-531 ; ISSN: 09477047 ; Faraji, M ; Sharif University of Technology
Abstract
RGO/TiO2NTs/Ti electrodes with high surface area and good capacitive characteristics were prepared by simple electrochemical reduction of graphene oxide (GO) onto the previously formed TiO2 nanotubes. Microstructure studies show that reduced graphene oxide (RGO) having high surface area has been deposited onto the TiO2NT arrays. The electrochemical capacitive behaviors of the obtained electrodes were investigated by cyclic voltammetry (CV), galvanostatic charge–discharge studies, and electrochemical impedance spectroscopy (EIS) in 1 M H2SO4 solution. The electrochemical data demonstrated that the electrodes displayed specific capacitance of 410 F g−1 at the current density of 50 A g−1 and...
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
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...
Hierarchical Co3O4/Co(OH)2 nanoflakes as a supercapacitor electrode: experimental and semi-empirical model
, Article ACS Applied Materials and Interfaces ; Volume 7, Issue 21 , 2015 , Pages 11172-11179 ; 19448244 (ISSN) ; Naseri, N ; Moshfegh, A. Z ; Sharif University of Technology
American Chemical Society
2015
Abstract
In this research, facile and low cost synthesis methods, electrodeposition at constant current density and anodization at various applied voltages, were used to produce hierarchical cobalt oxide/hydroxide nanoflakes on top of porous anodized cobalt layer. The maximum electrochemical capacitance of 601 mF cm-2 at scan rate of 2 mV s-1 was achieved for 30 V optimized anodization applied voltage with high stability. Morphology and surface chemical composition were determined by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analysis. The size, thickness, and density of nanoflakes, as well as length of the porous anodized Co layer were measured about 460 ± 45 nm,...
Role of nitrogen doping at the surface of titanium nitride thin films towards capacitive charge storage enhancement
, Article Journal of Power Sources ; Volume 359 , 2017 , Pages 349-354 ; 03787753 (ISSN) ; Chaker, M ; Achour, H ; Arman, A ; Islam, M ; Mardani, M ; Boujtita, M ; Le Brizoual, L ; Djouadi, M. A ; Brousse, T ; Sharif University of Technology
Abstract
We recently reported an impressive cycling stability (over 20,000 cycles) of titanium nitride (TiN) electrodes with high specific capacitance. It is anticipated that nitrogen (β−N) doping in the oxidized surface of TiN film plays a crucial role in charge storage mechanism and stability of this material. In this work, we offer an evidence on the effect of β−N doping on improvement in specific capacitance of vacuum annealed TiN thin films. The annealing of the TiN films leads to the diffusion of the excess β−N from sub-surface to oxidized TiN film surface without further oxidation of the electrode surface. We demonstrate an increase in the TiN areal capacitance upon an increase in the amount...
Facile deposition of porous fluorine doped tin oxide by Dr. Blade method for capacitive applications
, Article Ceramics International ; 2020 ; Tajabadi, F ; Dastan, D ; Sangpour, P ; Shi, Z ; Taghavinia, N ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
Three-dimensional macroporous fluorine-doped tin oxide (p-FTO) films were successfully deposited using commercial ink of FTO powder and SnCl2 salt via Dr. Blade method. Various features of p-FTO thin films were studied as a function of the ink composition and sintering temperature. The morphological studies corroborated formation of porous, uniform, and crack-free FTO films after annealing at 300 °C for 10 min in air. X-ray diffraction pattern demonstrated development of highly crystalline FTO films. The lowest sheet resistance of 47 Ω/□ was obtained for the p-FTO film with a thickness of 21 μm. The capacitance of thin p-FTO films was investigated using a three-electrode system and the...
Fabrication of a 2.8 V high-performance aqueous flexible fiber-shaped asymmetric micro-supercapacitor based on MnO2/PEDOT:PSS-reduced graphene oxide nanocomposite grown on carbon fiber electrode
, Article Journal of Materials Chemistry A ; Volume 8, Issue 37 , 2020 , Pages 19588-19602 ; Shahrokhian, S ; Soavi, F ; Sharif University of Technology
Royal Society of Chemistry
2020
Abstract
Flexible and lightweight fiber-shaped micro-supercapacitors have attracted tremendous attention as next-generation portable electronic devices, due to their high flexibility, tiny volume, and wearability. Herein, we successfully fabricated a ternary binder-free nanocomposite of MnO2/PEDOT:PSS-rGO on a carbon fiber substrate for application in high performance fiber-shaped micro-supercapacitors. The synergistic effects of the different components in the fiber-shaped electrode help to deliver a high specific capacitance of 2.9 F cm-2 (194 F cm-3 and 550 mF cm-1) at a current density of 5 mA cm-2 and a long cycle life with 95% capacitance retention after 5000 cycles in 1 M Na2SO4 electrolyte. A...
Fabrication of porous polyphosphate carbon composite on nickel foam as an efficient binder-less electrode for symmetric capacitive deionization
, Article Separation and Purification Technology ; Volume 276 , 2021 ; 13835866 (ISSN) ; Mahdi Ahadian, M ; Shahrokhian, S ; Amini, M. K ; Sharif University of Technology
Elsevier B.V
2021
Abstract
An efficient and commercially available method is introduced for preparation of a binder-free electrode for capacitive deionization (CDI) application. An interconnected porous composite consisting of polyphosphate (PPO), graphene (Gr) and multi-walled carbon nanotube (CNT) is fabricated and assembled on a Ni foam substrate to prepare a binder-free electrode (Ni/PPOGrCNT). The resulting electrodes were characterized using various instrumental techniques such as TEM, SEM, EDS, XRD, FT-IR, Raman, XPS and XRF. Characterization results indicated that a mesoporous PPO structure is formed on a 3D assembly of carbon backbone. Accordingly, the 3-D porous structure facilitates the ion diffusion into...
Modeling, Identification and Control of an Electrostatically Suspended Gyroscope
, M.Sc. Thesis Sharif University of Technology ; Ghanbarpour Asl, Habib (Supervisor)
Abstract
This paper presents a novel method for satellite attitude determination, using Electrostatically Suspended gyroscope (ESG). In this method, two superconducting rings rotated around a spherical rotor, which causes a variable flux in rings. So according to faraday’s law of induction, a voltage will be induced in the rings. Using this voltage and a kalman filter, attitude of satellite will be determined. ESG works precisely, when the rotor is maintain at the center of gyroscope cavity, between three pairs of circular electrode, so a backstepping control algorithm will be designed In order to this purpose. The performance of attitude determination using this ESG and designed control algorithm is...
Investigation of the Ion Migration Mechanism and its Effect on the Slow Response of Perovskite Solar Cells
, Ph.D. Dissertation Sharif University of Technology ; Taghavinia, Nima (Supervisor) ; Mohammadpour, Raheleh (Supervisor)
Abstract
In recent years, organo-metal perovskite solar cells have attracted remarkable attention due to their low cost manufacturing method as well as the rapid growth of efficiency. Despite the fast growing efficiency of organo-metal perovskite solar cells, there are big challenges around their low stability under real operational condition. In addition to extrinsic parameters like oxygen and humidity, intrinsic instability of perovskite rises mainly from ion migration in perovskite film. In order to understand the ion migration and its effect on photovoltaic parameters of the devices, appropriate characterizations and analysis are needed. Since ions are much slower compare to electrons, their...
Statistical study of nano-scale VLSI interconnect crosstalk and its induced power estimation
, Article 2012 2nd IEEE CPMT Symposium Japan, ICSJ 2012, 10 December 2012 through 12 December 2012 ; December , 2012 ; 9781467326551 (ISBN) ; Sarvari, R ; Seyedolhosseini, A ; Sharif University of Technology
2012
Abstract
Crosstalk due to the capacitive and inductive coupling has adverse effect on the circuit performance. In this paper crosstalk voltage and its induced power are studied for a stochastic environment bus with specific physical structure. Input switching pattern, driver, and load are swept in wide range for VLSI application to study crosstalk variation. Crosstalk and power is extracted to drive mean and standard deviation for implemented structures. The crosstalk mean and its induced power get lower with increasing of the load and driver resistance. This phenomenon is proportional to shrinking the technology
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...
In-situ fabrication of nanosheet arrays on copper foil as a new substrate for binder-free high-performance electrochemical supercapacitors
, Article Journal of Electroanalytical Chemistry ; Volume 802 , 2017 , Pages 48-56 ; 15726657 (ISSN) ; Shahrokhian, S ; Sharif University of Technology
Abstract
A facile hydrothermal method and subsequent electroactivation have been developed to fabricate three-dimensional (3D) CuO nanosheet arrays on the copper foil substrate, which can be used directly as a binder-free electrode for supercapacitor applications. Under optimum conditions, by using this facile method, a high capacitance of 125 mF/cm2 at a current density of 0.3 mA/cm2 is obtained. The prepared supercapacitor showed a good rate capability (46.4% capacitance retention, when the current density is increased to more than 30 times) and an excellent cyclability (more than 88% capacitance retention after 3000 cycles). © 2017 Elsevier B.V