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intermodulation
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Design and Fabriaction of a Power Amplifier and Its Linearizer Using Analog Predistortion Method
, M.Sc. Thesis Sharif University of Technology ; Banai, Ali (Supervisor)
Abstract
Modern communication systems,while demanding high power efficiency, suffer from the inherent nonlinearty effects. Such a problem becomes more critical in LEO satellites, in which there are fundamental power limitations. Considering that the main source of nonlinear effects are power amplifiers, one of the most common methods to improve signal quality in a transmitter, meanwhile maintaining power efficiency, is to utilize linearization techniques for power amplifiers. This project consists of two parts. The first is to design and fabricate a power amplifier for the desired frequency (2.4 GHz) and power requirements (3 W). The other is design and fabrication of a linearizer and matching it to...
Cosintering of powder injection molding parts made from ultrafine WC-Co and 316L stainless steel powders for fabrication of novel composite structures
, Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Volume 41, Issue 1, January 2010, Pages 233-241 ; Petzoldt, F ; Sharif University of Technology
Abstract
Abstract Sintering response and phase formation during sintering of WC-Co/316L stainless steel composites produced by assembling of powder injection molding (PIM) parts were studied. It is shown that during cosintering a significant mismatch strain (> 4 pct) is developed in the temperature range of 1080° C to 1350° C. This mismatch strain induces biaxial stresses at the interface, leading to interface delamination. Experimental results revealed that sintering at a heating rate of 20 K/min could be used to decrease the
Modeling of unusual nonlinear behaviors in superconducting microstrip transmission lines
, Article Physica C: Superconductivity and its Applications ; Volume 486 , March , 2013 , Pages 37-42 ; 09214534 (ISSN) ; Farzaneh, F ; Fardmanesh, M ; Sharif University of Technology
2013
Abstract
There are unusual nonlinear behaviors in superconducting materials, especially at low temperatures. This paper describes the procedure to reliably predict this nonlinearity in superconducting microstrip transmission lines (SMTLs). An accurate nonlinear distributed circuit model, based on simultaneously considering of both quadratic and modulus nonlinearity dependences, is proposed. All parameters of the equivalent circuit can be calculated analytically using proposed closed-form expressions. A numerical method based on Harmonic Balance approach is used to predict nonlinear phenomena like intermodulation distortions and third harmonic generations. Nonlinear analyses of the SMTLs at the...
Current Distribution and Nonlinearity of Open-Ends and Gaps in Superconducting Microstrip Structures
, Article Journal of Superconductivity and Novel Magnetism ; Volume 26, Issue 5 , May , 2012 , PP, 1821-1825 ; 15571939 (ISSN) ; Farzaneh, F ; Fardmanesh, M ; Sharif University of Technology
2012
Abstract
Superconducting devices are known to produce nonlinear effects. In planar structures, these nonlinearities depend on the current distribution on the strip, which definitely depends on the structure of device. This paper used a numerical method based on 3D-FEM to obtain the current distribution in the open-ends and gaps in the superconducting microstrip structures. This is used to present the nonlinear distributed circuit modeling of these discontinuities and its impact on the nonlinear phenomenon. This nonlinear circuit model is used in the Harmonic Balance (HB) method to analyze nonlinearity in the superconducting microwave devices. Therefore, this simple accurate enough nonlinear circuit...
Analysis and optimization of SFDR in differential active-RC filters
, Article IEEE Transactions on Circuits and Systems I: Regular Papers ; Volume 59, Issue 6 , December , 2012 , Pages 1168-1177 ; 15498328 (ISSN) ; Bakhtiar, M ; Sharif University of Technology
Abstract
This paper presents a method for optimizing SFDR in differential active-RC filters. Simple analytical expressions for noise and third-order intermodulation (IM3) distortion in active-RC filters are derived. The nonlinear behavior of two-stage Miller-compensated op amps, which are extensively used in active-RC implementations, is also modeled. These expressions and models are used to maximize SFDR in active-RC filters by means of proper admittance scaling and optimizing the share of each op amp in the total power consumption. It is shown that both the power consumption of the filter and its area can be significantly reduced, for a given SFDR, by exploiting the presented method
Cosintering of powder injection molding parts made from ultrafine WC-Co and 316L stainless steel powders for fabrication of novel composite structures
, Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Volume 41, Issue 1 , 2010 , Pages 233-241 ; 10735623 (ISSN) ; Petzoldt, F ; Sharif University of Technology
Abstract
Sintering response and phase formation during sintering of WC-Co/316L stainless steel composites produced by assembling of powder injection molding (PIM) parts were studied. It is shown that during cosintering a significant mismatch strain (>4 pct) is developed in the temperature range of 1080 °C to 1350 °C. This mismatch strain induces biaxial stresses at the interface, leading to interface delamination. Experimental results revealed that sintering at a heating rate of 20 K/min could be used to decrease the mismatch strain to <2 pct. Meanwhile, WC is decomposed at the contact area and the diffusion of C and Co into the iron lattice results in the formation of a liquid and MC and M6C...
Study the sintering behavior of nanocrystalline 3Y-TZP/430L stainless-steel composite layers for co-powder injection molding
, Article Journal of Materials Science ; Volume 44, Issue 5 , 2009 , Pages 1264-1274 ; 00222461 (ISSN) ; Simchi, A ; Sharif University of Technology
2009
Abstract
Recently, co-powder injection molding process (2C-PIM) has attained considerable interest to fabricate complex-shaped functional materials. The aim of this work is to study the sintering compatibility between nanocrystalline yttria-stabilized zirconia (3Y-TZP) and PIM grade 430L stainless steel (SS) powders, which is the utmost important step in the 2C-PIM process. To evaluate the mismatch strain development during the co-sintering, the isothermal and nonisothermal behaviors of the ceramic and metal powders were studied. Small bilayers of 3Y-TZP/430L were made by a powder metallurgy technique and the feasibility of simultaneous sintering and joining of the composite layer was examined....
Theory of optimal mixing in directly modulated laser diodes
, Article Scientia Iranica ; Volume 16, Issue 2 D , 2009 , Pages 157-162 ; 10263098 (ISSN) ; Cabon, B ; Sharif University of Technology
2009
Abstract
Using a simple nonlinear model based on rate equations, and by employing a harmonic balance method, we develop a theory of optimal mixing in directly modulated semiconductor laser diodes. We perform a consistent numerical solution to the mixing in laser diodes to the arbitrary accuracy and intermodulation index (m, n). Through numerical computations we demonstrate that there is an optimal bias in mixing, corresponding to a relaxation frequency, fr, coinciding with the subcarrier frequency, f1, at which the mixing power is maximized nearly simultaneously for all intermodulation products, fmn. In terms of increasing the signal's current amplitude, it will be shown that it would result in a...
Estimation of practical Inter-Modulation Rejection values in a multi-loop feed-forward microwave power amplifier using Monte-Carlo method
, Article 2007 IEEE International Conference on Telecommunications and Malaysia International Conference on Communications, ICT-MICC 2007, Penang, 14 May 2007 through 17 May 2007 ; February , 2007 , Pages 632-637 ; 1424410940 (ISBN); 9781424410941 (ISBN) ; Hemmatyar, A ; Farzaneh, F ; Sharif University of Technology
2007
Abstract
Feed-forward is one of the best methods for linearizing microwave power amplifiers, but due to device tolerance in implementation of the system components, the practical Inter-Modulation Rejection (IMR) value may differ quite much from the theoretical IMR value. One of the methods to improve the practical performance of the system is using the multi-loop configuration. Here we have introduced the multi-loop feedforward systems and we have estimated the practical IMR values of the system using Monte-Carlo analysis. As the analysis shows, although the number of components in a multi-loop system is increased with respect to a simple feed-forward system, but the difference between the practical...