1,721,099 research outputs found
Artificial neural network based macromodeling approach for two-port RF MEMS resonating structures
No full textIn this paper, we propose an efficient approach for analysis, design, and optimization of two-port radio frequency microelectromechanical systems (RF MEMS) resonating structures. Methodology utilizes finite element method (FEM) for the prediction of electromechanical responses and fast/accurate mapping with an artificial neural networks (ANNs) technique, toward a final goal - a generic macromodel compatible with modern circuit computer aided design (CAD) tools. Thus, instead of using memory and time demanding full-wave analysis or more extensive and expensive design process using multiple fabrication cycles, a simple yet accurate circuit simulator compatible modeling and optimization procedure is developed
Design and optimisation of one-port RF MEMS resonators and related integrated circuits using ANN-based macromodelling approach
No full textThe authors propose a modelling methodology which combines finite element method (FEM) and artificial neural networks (ANNs) techniques for the design and optimisation of integrated circuits (ICs) incorporating one-port radio frequency microelectromechanical systems (RF MEMS) resonating structures. The FEM is employed to predict the electro-mechanical performance of MEMS resonators. ANNs are utilised to model complex relationships between the physical parameters of the MEMS resonator and the corresponding electrical equivalent circuit parameters. These parameters are extracted directly from the FEM analysis and used for training the ANNs. It is shown that the relative error of the ANN model for a single MEMS device is less than 0.5% while the computational time is more than 40 times reduced compared to the FEM. To extend the capabilities of the proposed methodology, the developed ANN model is implemented into a commercially available circuit simulator, Agilent's Advanced Design System (ADS). This allows a seamless modelling process for the design and optimisation of MEMS resonators embedded ICs at both the device and circuit levels. As an example, a 30 MHz Pierce oscillator with the ANN model of a free-free beam MEMS resonator is optimised within the circuit simulato
Design and optimization of RF ICs with embedded linear macromodels of multiport MEMS devices
No full textIn this paper, we demonstrate efficient modeling approach for simulation, analysis, design, and optimization of multiport radio frequency microelectromechanical systems (RF MEMS) resonating structures embedded in RF circuits. An in-house finite element method (FEM) solver is utilized to develop accurate and efficient macromodels that capture all the essential characteristics of the device. Using the datasets generated from the FEM simulations, the artificial neural network models are trained for two-way mapping between the physical input and electrical output parameters. Realized model is implemented in a circuit simulator, enabling a simple yet accurate circuit simulator compatible modeling and optimization procedure instead of memory and time demanding FEM analysis. The derivation of dynamic macromodels with preserved electromechanical behavior of the multiport resonating structures is also presented. Capabilities of the proposed approach are demonstrated with several examples featuring capacitively actuated MEMS resonating structures: a clamped-clamped beam, a free-free beam, and a coupled clamped-clamped beam. (C) 2007 Wiley Periodicals, In
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Millimeter-Wave GaN Solid-State Arrays
Get PDFMillimeter-wave applications above Ka-band have become increasingly important for both the military and commercial sector. With the overcrowded spectrum at lower microwave frequencies, more systems are demanding the use of unlicensed spectrum space at V-, W-band and beyond. Data communications for wireless links are requiring frequencies greater than 75 GHz to achieve high data rates up 80 Gbps. Scalable W-band phased arrays using silicon technology have been demonstrated for automotive radar, imaging and communication. Technologies such as Gallium-Nitride (GaN) have been pushing high-frequency performance with operating frequencies in the hundreds of GHz allowing the capability for solid-state high-power transmitters. General challenges forW-band high-power solid-state transmitters are achieving high effective radiated power (ERP) in a small footprint and with reasonable efficiency for space constrained applications. Recent advances in GaN technology with cutoff frequencies ft > 150 GHz achieve power densities as highas 3W/mm at W-band. For very high-power applications many amplifiers are required to be combined and fed into an array for spatially coherently power combining. The need for multiple levels of power combining provides a trade off in terms of combining efficiency, heat dissipation, volume and co-design from the transistor to the radiating aperture. Each power amplifier (PA) module can have varying levels of power combining including device level within a monolithic microwave integrated circuit (MMIC) amplifier, thin-film and waveguided power combining, and spatial power combining to achieve the desired ERP.
This thesis focuses on the design and analysis of millimeter-wave MMIC power amplifiers for high effective radiated power (ERP) using three GaN research processes in development by the industry. W-band PAs are presented and predict state-of-the-art output power. Analysis of power combining efficiency anddegradation in power combiners and phased arrays caused by GaN-on-SiC semiconductor process variations is presented.</p
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