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    Design and Implementation of a Low-noise Direct Conversion Mixer with LO-2LO Method

    , M.Sc. Thesis Sharif University of Technology Kalami, Milad (Author) ; Medi, Ali (Supervisor)
    Abstract
    In this thesis, we try to design and implement a low noise, low power consumption CMOS direct conversion mixer with LO-2LO topology. Direct conversion mixers have two differential I,Q outputs. Because of zero intermediate frequency, flicker noise is critical. This mixer is designed for UHF band in TSMC CMOS 0.18µm technology. Total current consumption of I,Q mixer is less than 3mA .Voltage conversion gain is about 23 dB and DSB noise figure is less than 3.5 dB. Some conventional thermal and flicker noise cancellation has been used simultaneously to reduce noise figure. New noise cancellation techniques are proposed to get further improvement in noise figure with negligible extra current... 

    A fully analog side-band cancellation technique in radio-frequency transmitters

    , Article Microelectronics Journal ; Volume 53 , Volume 53 , 2016 , Pages 116-126 ; 00262692 (ISSN) Nikoofard, A ; Kananian, S ; Hadizadeh, E ; Fotowat Ahmady, A ; Sharif University of Technology
    Elsevier Ltd 
    Abstract
    In this paper, a new fully analog technique is proposed by means of which the adverse effects of frequency dependent gain/phase errors in quadrature transmitters are suppressed. Two separate phase and gain mismatch cancellation loops are implemented which search for the minimum side-band component. A new sign detection method is also introduced which makes sure the direction of the loop is correct. Analytical models and mathematical derivations have been presented which corroborates the circuit implementation. A proof of concept prototype using off-the-shelf components have also been measured which suggests 38-dB side-band rejection (SBR). Furthermore, the measured TX EVM and BER are... 

    An Analysis of Common Mode Voltage in Multi-level Matrix Converter

    , M.Sc. Thesis Sharif University of Technology Garousi, Bahram (Author) ; Oraee Mirzamani, Hashem (Supervisor)
    Abstract
    The matrix converter is an array of controlled bidirectional semi-conductor switches that allows direct ac–ac conversion without an intermediate dc link. This converter has several attractive features that have been investigated in the last two decades. Multilevel converter technology has become increasingly popular in recent years due to high power quality,high-voltage capability, low switching losses and low EMI issues.This paper is concerned with applying multilevel techniques to direct ac–ac power converters and concentrates on developing the concepts of space vector modulation for a multilevel matrix converter. The common-mode voltage produced by a modern power converter has been... 

    Direct conversion of methane to methanol over v 2O 5/Sio 2 catalyst in a fixed-bed reactor utilizing a CFD model

    , Article World Academy of Science, Engineering and Technology ; Volume 73 , 2011 , Pages 797-802 ; 2010376X (ISSN) Vafajoo, L ; Morteza, S ; Fattahi, M ; Sharif University of Technology
    Abstract
    A dynamic model of oxidation of methane to methanol has been developed in a fixed-bed reactor applying V2O5/SiO2 as the reaction catalyst. The standard k-? model with 10% turbulence amount performed. The effects of temperature (450- 500°C) and pressure (20-120 bar) with residence time of 3 seconds, on methane conversion and methanol or formaldehyde selectivity examined. Oxygen used as an oxidant and the amount of oxygen in feed was 5% mol/mol of methane amount. The results showed with increasing the conversion of methane from 0.66 to 1.52%, the selectivity to methanol decreased from 93.4% to 91.9%. The CFD modeling results showed reasonable agreement with the obtained experimental data of... 

    Circuit and system design for an 860-960 MHz RFID reader front-ends with Tx leakage suppression in 0.18 - μm CMOS technology

    , Article International Journal of Circuit Theory and Applications ; Volume 40, Issue 9 , MAR , 2012 , Pages 957-974 ; 00989886 (ISSN) Javidan, J ; Atarodi, S. M ; Luong, H. C ; Sharif University of Technology
    Wiley  2012
    Abstract
    This paper presents an RF Front-END for an 860-960thinspaceMHz passive RFID Reader. The direct conversion receiver architecture with the feedback structure in the RF front-end circuit is used to give good immunity against the large transmitter leakage and to suppress leakage. The system design considerations for receiver on NF and IIP3 have been discussed in detail. The RF Front-END contains a power amplifier (PA) in transmit chain and receive front-end with low-noise amplifier, up/down mixer, LP filter and variable-gain amplifier. In the transmitter, a differential PA with a new power combiner is designed and fabricated in a 0.18-μm technology. The chip area is 2.65 mm × 1.35 mm including... 

    A compact mixer and DAC for implementation of a direct conversion OQPSK transmitter

    , Article 2007 IEEE Region 10 Conference, TENCON 2007, Taipei, 30 October 2007 through 2 November 2007 ; 2007 ; 1424412722 (ISBN); 9781424412723 (ISBN) Chahardori, M ; Mehrmanesh, S ; Zamanlooy, B ; Atarodi, M ; Sharif University of Technology
    2007
    Abstract
    A compact low power circuit for implementation of a direct conversion OQPSK modulator is proposed. The circuit consists of a digital to analog converter, a low pass filter and an up-converter mixer. By embedding these three blocks, the circuit performance is enhanced and the total power consumption is reduced. The mixer is designed base on a Gilbert cell with on chip inductor loads. Instead of transconductance transistors of Gilbert cell, a fully deferential current mode DAC is used and proficiently a low pass filter is embedded between them and therefore the linearity of total system is improved. All of circuits are designed based on 0.18 μm CMOS technology with a single 1.8 volt power...