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    An analytical approach in analysis of local oscillator near-the-carrier AM noise suppression in microwave balanced mixers

    , Article IEEE Transactions on Microwave Theory and Techniques ; Volume 57, Issue 4 , 2009 , Pages 760-766 ; 00189480 (ISSN) Kheirdoost, A ; Banai, A ; Farzaneh, F ; Sharif University of Technology
    2009
    Abstract
    In this paper, a new formulation based on conversion matrix method is proposed to analyze near-the-carrier local ocillator (LO) noise down conversion to IF in microwave mixers. This method could be easily applied to analyze LO noise down conversion in any type of mixer. Practical results of this method have been compared with the envelope method and measurement results. It is shown that despite the conventional AM noise suppression in balanced mixers, the near-the-carrier LO noise suppression does not occur necessarily at the center frequency of hybrid in balanced mixers. AM noise suppression values are predicted precisely. © 2006 IEEE  

    Modeling active micromixers with multiple microstirrers using smoothed particle hydrodynamics

    , Article Scientia Iranica ; Vol. 21, issue. 4 , 2014 , pp. 1390-1402 ; ISSN: 10263098 Jafarian, A ; Pishevar, A ; Saidi, M. S ; Sharif University of Technology
    Abstract
    The smoothed particle hydrodynamics method is used to explore the effects of design parameters on the mixing efficiency of two types of active micromixer. First, the complex flow field and the mixing process of two separated fluids in a square mixing chamber with nine symmetric microstirrers are simulated. The influence of design parameters, such as the microstirrer rotation arrangement and the angular velocity of the microstirrer, on the mixing performance, is investigated. The mixing index parameter on ten control points is calculated and the average mixing index is compared for different cases. Simulations illustrate that the rotation arrangement of microstirrers is a key parameter in the... 

    Detail study on improving micro/nano gas mixer performances in slip and transitional flow regimes

    , Article Sensors and Actuators, B: Chemical ; Volume 218 , October , 2015 , Pages 78-88 ; 09254005 (ISSN) Darbandi, M ; Sabouri, M ; Sharif University of Technology
    Elsevier  2015
    Abstract
    The mixer geometry has substantial effect on mixing performance of different micro/nanomixers. Despite past numerous studies dedicated to mixing of liquid flow streams, there are less efforts to investigate the geometry effects on gas mixing performances. In this work, we focus on gas-gas mixing through different micro/nanoscale mixers under slip and transitional flow regimes. We use the direct simulation Monte Carlo (DSMC) method to provide accurate and reliable results in such flow regimes. To extend our study, we implement different geometrical parameters in our consideration including the mixer size, the impact angle between two incoming gas streams, and the contraction height located in... 

    Analyzing mixing quality in a curved centrifugal micromixer through numerical simulation

    , Article Chemical Engineering and Processing: Process Intensification ; 2017 ; 02552701 (ISSN) Shamloo, A ; Vatankhah, P ; Akbari, A ; Sharif University of Technology
    Elsevier B.V 
    Abstract
    The Lab On a CD (LOCD), also known as Centrifugal Microfluidics, has evolved into a sophisticated platform for performing biomedical assays due to its marvelous miniaturization and accurate simulation of biological reactions. Among the numerous applications of the LOCD is fluid mixing. In this paper a centrifugal, serpentine micromixer is simulated and reformed toward better mixing performance. The micromixer was chosen to be curved as a curved design was found to be thrice as functional and compact as a rectilinear design, mixing-wise. The two angular velocity and opening radius parameters were originally hypothesized to affect mixing performance. Effect of angular velocity was studied over... 

    Mixing performance of T, Y, and oriented Y-micromixers with spatially arranged outlet channel: evaluation with villermaux/dushman test reaction

    , Article Microsystem Technologies ; 2016 , Pages 1-14 ; 09467076 (ISSN) Rahimi, M ; Azimi, N ; Parsamogadam, M. A ; Rahimi, A ; Masahy, M. M ; Sharif University of Technology
    Springer Verlag  2016
    Abstract
    This study aims to investigate the micromixing performance of three basic types of spatial shaped micromixers. New configurations of T, Y, and oriented Y-spatial mixers were designed with change in the angles of the confluence and the outlet channel to achieve the efficient micromixing. These micromixers offer advantages that are not attainable with the typical types of these mixers. Experimental tests were carried out in the laminar flow regime and the mixing efficiency was evaluated using Villermaux/Dushman test reaction. The geometries of the channels were cylindrical with the length of 30 mm and the diameter of 800 μm. The experimental results show that the angle of outlet channel has a... 

    Mixing performance of T, Y, and oriented Y-micromixers with spatially arranged outlet channel: evaluation with Villermaux/Dushman test reaction

    , Article Microsystem Technologies ; Volume 23, Issue 8 , 2017 , Pages 3117-3130 ; 09467076 (ISSN) Rahimi, M ; Azimi, N ; Parsamogadam, M. A ; Rahimi, A ; Masahy, M. M ; Sharif University of Technology
    Springer Verlag  2017
    Abstract
    This study aims to investigate the micromixing performance of three basic types of spatial shaped micromixers. New configurations of T, Y, and oriented Y-spatial mixers were designed with change in the angles of the confluence and the outlet channel to achieve the efficient micromixing. These micromixers offer advantages that are not attainable with the typical types of these mixers. Experimental tests were carried out in the laminar flow regime and the mixing efficiency was evaluated using Villermaux/Dushman test reaction. The geometries of the channels were cylindrical with the length of 30 mm and the diameter of 800 μm. The experimental results show that the angle of outlet channel has a... 

    Analyzing mixing quality in a curved centrifugal micromixer through numerical simulation

    , Article Chemical Engineering and Processing: Process Intensification ; Volume 116 , 2017 , Pages 9-16 ; 02552701 (ISSN) Shamloo, A ; Vatankhah, P ; Akbari, A ; Sharif University of Technology
    Elsevier B.V  2017
    Abstract
    The Lab On a CD (LOCD), also known as Centrifugal Microfluidics, has evolved into a sophisticated platform for performing biomedical assays due to its marvelous miniaturization and accurate simulation of biological reactions. Among the numerous applications of the LOCD is fluid mixing. In this paper a centrifugal, serpentine micromixer is simulated and reformed toward better mixing performance. The micromixer was chosen to be curved as a curved design was found to be thrice as functional and compact as a rectilinear design, mixing-wise. The two angular velocity and opening radius parameters were originally hypothesized to affect mixing performance. Effect of angular velocity was studied over... 

    Active microfluidic micromixer design using ionic polymer-metal composites

    , Article 27th Iranian Conference on Electrical Engineering, ICEE 2019, 30 April 2019 through 2 May 2019 ; 2019 , Pages 371-375 ; 9781728115085 (ISBN) Annabestani, M ; Mohammadzadeh, H ; Aghassizadeh, A ; Azizmohseni, S ; Fardmanesh, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2019
    Abstract
    In most of the microfluidic applications, it is necessary to have a mixed fluid from the beginning, but in microchannels, due to facing with low Reynolds flows, the fluids flow in the channel by the laminar regimes. Hence the mixing process is a challenging problem and researchers are trying to present fast and reliable micromixers. In this paper, using Ionic Polymer-Metal Composites (IPMCs), an active micromixer has been designed. To investigate the appropriateness of IPMC, using experimental and simulation tests, we show that the IPMC actuator is a potential candidate as an active element of microfluidic micromixers  

    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 Mir-Moghtadaei, S. V ; 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... 

    Using the direct simulation Monte Carlo method to study the effect of wall temperature variation on gas mixing evolution through micro T-mixers

    , Article 11th International Energy Conversion Engineering Conference ; 2013 Darbandi, M ; Sabouri, M ; Lekzian, E ; Schneider, G. E ; Sharif University of Technology
    2013
    Abstract
    In this work, we study the gas mixing behavior in a micro T-mixer using the direct simulation Monte Carlo (DSMC) method. The gas mixing process is monitored through a T-mixer, which is fed by two different CO and N2 gases; flowing into the T-mixer through the upper and lower inlets. We investigate the effects of axial and lateral wall temperature gradients on the mixing evolution at different rarefaction levels. The achieved results show that any temperature difference between the channel walls would result in an increase in mixing length for the chosen wall temperature gradient ranges and the studies pressure cases. Our observations show that a positive temperature gradient toward the... 

    A 1-mW current reuse quadrature RF front-end for GPS L1 band in 0.18μm CMOS

    , Article 2012 19th IEEE International Conference on Electronics, Circuits, and Systems, ICECS 2012, Seville, Seville, 9 December 2012 through 12 December 2012 ; 2012 , Pages 157-160 ; 9781467312615 (ISBN) Jalili, H ; Fotowat Ahmady, A ; Jenabi, M ; Sharif University of Technology
    2012
    Abstract
    A new low-power current reuse topology is proposed for the GPS receiver's RF front-end that combines the higher conversion gain and suppressed noise figure characteristics of cascade structures with the low power consumption of stacked architectures. The presented circuit, called 1.5-stage LMV cell, consists of LNA, Mixer and VCO (LMV) in such a formation that boosts LNA gain and suppresses mixer's noise figure by cascading the two stages while reusing their currents in the two stacked quadrature VCOs and placing the mixer's upper tree switches at the vicinity of on-off regions. The circuit is designed and its layout is generated in TSMC 0.18μm CMOS technology. Post-layout simulations using... 

    Down-conversion self-oscillating mixer by using CMOS technology

    , Article Proceedings - 2012 IEEE 8th International Colloquium on Signal Processing and Its Applications, CSPA 2012 ; 2012 , Pages 33-36 ; 9781467309615 (ISBN) Kouchaki, M ; Zahedi, A ; Sabaghi, M ; Ameri, S. R. H ; Niyakan, M ; Sharif University of Technology
    2012
    Abstract
    In this paper a self-oscillating mixer is presented fundamental signal generated by the oscillator subcircuit in the mixing process. The oscillator core consumes 3mA of current from a 1.8 V DC supply and results in an output power of -0.867 dBm per oscillator, and a measured phase noise of -91, -102 and -108 dBc/Hz at 100 KHz, 600 KHz and 1 MHz from the carrier, respectively. In the mixing process the proposed mixer achieved IIP3 of 0 dBm with conversation gain of 1.93 dB. The circuit was designed and simulated in 0.18-μm CMOS technology by ADS2010  

    Rarefaction effects on gas mixing in micro- and nanoscales

    , Article ASME 2016 5th International Conference on Micro/Nanoscale Heat and Mass Transfer, MNHMT 2016, 4 January 2016 through 6 January 2016 ; Volume 1 , 2016 ; 9780791849651 (ISBN) Darbandi, M ; Sabouri, M ; Heat Transfer Division ; Sharif University of Technology
    American Society of Mechanical Engineers  2016
    Abstract
    We present the rarefaction effects on diffusive mass transport in micro- and nanoscales using the results of direct simulation Monte Carlo DSMC method. Unlike the previous investigations, the momentum and heat contributions are eliminated from the computations via uniform velocity, pressure, and temperature field considerations. The effects of global Knudsen number on the diffusion phenomenon are studied for the same Peclet number and a unique mixer shape. The results indicate that there is considerable weakening in diffusion mechanism for high Knudsen number cases. As a result, the non-dimensional diffusive mass fluxes would decrease and the non-dimensional mixing length would increase as... 

    Numerical simulation of centrifugal serpentine micromixers and analyzing mixing quality parameters

    , Article Chemical Engineering and Processing: Process Intensification ; Volume 104 , 2016 , Pages 243-252 ; 02552701 (ISSN) Shamloo, A ; Madadelahi, M ; Akbari, A ; Sharif University of Technology
    Elsevier, B.V  2016
    Abstract
    Centrifugal microfluidics or the Lab on a CD (LOCD) has developed vast applications in biomedical researches and analyses. Fluid mixing is an application of the LOCD. In this paper, multiple centrifugal micromixers were simulated. Various parameters were originally presumed to have an effect on mixing performance. These parameters include inlet angle, angular velocity, cross-sectional profile, perpendicular length ratio and the number of channels in series. They were each analyzed through simulations. It was gathered that the inlet angle does not significantly affect the mixing quality. Increasing angular velocity steadily increases mixing quality for all geometries. The vertical triangular... 

    Three-dimensional numerical simulation of a novel electroosmotic micromixer

    , Article Chemical Engineering and Processing: Process Intensification ; Volume 119 , 2017 , Pages 25-33 ; 02552701 (ISSN) Shamloo, A ; Madadelahi, M ; Abdorahimzadeh, S ; Sharif University of Technology
    Elsevier B.V  2017
    Abstract
    Lab-on-a-chip (LOC) systems have been widely used in chemical and medical analyses. In this study, a novel T-shaped electroosmotic micromixer was simulated and the effects of different parameters on the mixing process were examined. These parameters include; inlet angle, number of conducting hurdles, arrangements of the hurdles, geometry of hurdles and chambers, aspect ratios of the channel cross-sectional profile, hurdle radius, and depth. It was found that the inlet angle has a direct influence on mixing index (σ). The effect of various number of hurdles (one, two, three and four hurdles) and their orientations was investigated. Simulations revealed that using two conducting hurdles is the... 

    Parametric study on mixing process in an in-plane spiral micromixer utilizing chaotic advection

    , Article Analytica Chimica Acta ; Volume 1022 , 2018 , Pages 96-105 ; 00032670 (ISSN) Vatankhah, P ; Shamloo, A ; Sharif University of Technology
    Abstract
    Recent advances in the field of microfabrication have made the application of high-throughput microfluidics feasible. Mixing which is an essential part of any miniaturized standalone system remains the key challenge. This paper proposes a geometrically simple micromixer for efficient mixing for high-throughput microfluidic devices. The proposed micromixer utilizes a curved microchannel (spiral microchannel) to induce chaotic advection and enhance the mixing process. It is shown that the spiral microchannel is more efficient in comparison to a straight microchannel, mixing wise. The pressure drop in the spiral microchannel is only slightly higher than that in the straight microchannel. It is... 

    Quantifying the direct influence of diffusive mass transfer in rarefied gas mixing simulations

    , Article Journal of Fluids Engineering, Transactions of the ASME ; Volume 140, Issue 3 , March , 2018 ; 00982202 (ISSN) Darbandi, M ; Sabouri, M ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME)  2018
    Abstract
    This work utilizes the direct simulation Monte Carlo (DSMC) calculations and examines the influence of rarefication on the mixing length and effective diffusion coefficient in a two-species mixing problem. There have been efforts in past rarefied mixing flow studies to bridge between the mixing evolution rate and Knudsen number. A careful review of those efforts shows that the past derived relations did not determine the weights of Reynolds (or Peclet) number in the rarefaction influences. Although they indicated that an increase in Knudsen would decrease the mixing length, such reductions were primarily due to the Reynolds (or Peclet) reduction. Therefore, those studies could not explicitly... 

    Enhancing active electro-kinetic micro-mixer efficiency by introducing vertical electrodes and modifying chamber aspect ratio

    , Article Chemical Engineering and Processing - Process Intensification ; Volume 142 , 2019 ; 02552701 (ISSN) Maleki Bagherabadi, K ; Sani, M ; Saidi, M. S ; Sharif University of Technology
    Elsevier B.V  2019
    Abstract
    Micro-mixers are considered as vital components of Micro Total Analysis systems (μTAS). Major objective in the design of micro-mixers is achieving high mixing quality in short mixing times. In this paper, numerical simulation of some micro-mixer designs has been carried out to understand the detailed flow pattern and thereby to propose modifications for improving mixing efficiency. It is well known that inducing convection will provide turbulent like behavior with corresponding mixing enhancement. In micro systems to drive the flow, electro-osmotic force is usually used by introducing electrodes. In this work, mixing electrodes have been implemented to induce convection and eddies. This... 

    A new non-dimensional parameter to obtain the minimum mixing length in tree-like concentration gradient generators

    , Article Chemical Engineering Science ; Volume 195 , 2019 , Pages 120-126 ; 00092509 (ISSN) Rismanian, M ; Saidi, M. S ; Kashaninejad, N ; Sharif University of Technology
    Elsevier Ltd  2019
    Abstract
    Microfluidic-based concentration gradient generators (CGGs) have a number of applications in chemical, biological and pharmaceutical studies. Thus, precise design of the microfluidic system is crucial to maintaining the desired concentration gradient in microchannels. One of the design considerations is the length of microchannels in the structure of a CGG. A CGG with a short length fails to provide the complete diffusive mixing, while the size of the microchip would unfavorably increase by incorporating a long CGG. Considering a CGG as a tree-like structure consisting of T-shaped micromixers, the mixing process of the species at a straight microchannel has been solved analytically. Herein,... 

    Multiphysics analysis and practical implementation of a soft μ-actuator- based microfluidic micromixer

    , Article Journal of Microelectromechanical Systems ; Volume 29, Issue 2 , 2020 , Pages 268-276 Annabestani, M ; Azizmohseni, S ; Esmaeili Dokht, P ; Bagheri, N ; Aghassizadeh, A ; Fardmanesh, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2020
    Abstract
    Electroactive-Polymers (EAPs) are one of the best soft $mu $ -actuators with great biomedical applications. Ionic ones (i-EAPs) have more promising features and have adequate potential for using in the active microfluidic devices. Here, as a case study, we have designed and fabricated a microfluidic micromixer using an i-EAP named Ionic Polymer-Metal Composite (IPMC). In microfluidics, active devices have more functionality but due to their required facilities are less effective for Point of Care Tests (POCTs). In the direction of solving this paradox, we should use some active components that they need minimum facilities. IPMC can be one of these components, hence by integrating the IPMC...