1,721,069 research outputs found
Comparative Study on Pre-Distortion/Calibration Methods for Current-Steering Digital-to-Analog Converters
No full textThis paper introduces a variety of different pre-distortion/calibration methods for current-steering digital-to-analog converters (CS-DAC) and compares their respective performance. The comparison is done through simulations of the different methods with a static CS-DAC model in MATLAB and the subsequent calculation of the signal-to-distortion ratio (SDR) and the spurious-free dynamic range (SFDR). Since the requirements for high-speed, high-precision applications are becoming more and more stringent on the data converters the need for calibration methods becomes also increasingly important. A quantitative comparison can help to decide on the right method for different applications in terms of reducing the distortions resulting from the static current cell mismatch of CS-DACs. This paper extends upon the previous research by using different input signal types for the simulations
A Model-Based Approach Digital Pre-Distortion Method for Current-Steering Digital-to-Analog Converters
No full textThis paper presents a novel static digital pre-distortion (DPD) method for a current-steering digital-to-analog converter (CS-DAC). The proposed method utilizes the knowledge of the current cell array architecture to calculate the static mismatch currents of the cells. The mismatch values are stored in memory and added to the original input code to generate the new pre-distorted input word. The converter corrects the static error with its own current cells without incorporating an additional calibration DAC (CALDAC) or programmable current sources. This results in a reduction in area, power and simulation run times because of the simpler circuit design. An Overflow-Cell-Selection (OCS) is introduced as a novel solution to further enhance the static linearity of the converter. It also can be implemented as a software solution for already existing DAC designs which do not have an integrated DPD and lab/measurement equipment (e.g., arbitrary wave generator (AWG)). This poses as a strong differentiation factor compared to other state-of-the-art static DPD methods. The evaluation of the proposed DPD is done via simulations in MATLAB and on-chip measurements with a 14-bit CS-DAC in 16 nm. Single tone measurements show a performance gain of the total harmonic distortion (THD) of 12 dB
Static Digital Pre-Distortion Method for High-Speed Current-Steering Digital-to-Analog Converters
No full textThis paper presents a static digital pre-distortion (DPD) method for a current-steering digital-to-analog converter (CS-DAC). The proposed model utilizes the knowledge of the current cell array architecture to calculate the static mismatch currents of the cells. The mismatch values of all cells are stored in memory and added to the original input code to generate the new pre-distorted input word. The converter corrects the static error with its own current cells without incorporating an additional calibration DAC (CALDAC) or programmable current sources. This results in a reduction in area, power and simulation run times because of the simpler circuit design. The proposed method is able to use an information signal for the calibration phase, thus it is possible to be implemented as a background calibration. The evaluation of the proposed DPD is done via simulations in MATLAB with a 14-bit static CS-DAC model. The results show a performance gain of the signal-to-noise-plus-distortion ratio (SNDR) of up to 16dB
Switched state-space model for high speed current-steering digital-to-analog converter
No full textThis paper proposes a time domain behavioral model for dynamic switching effects of a current-steering digital-to-analog converter (CS-DAC) which shortens the simulation run time while still providing reasonable accuracy. Instead of implementing it with commonly used behavioral models such as the Wiener model, the analysis framework is obtained with the switched state-space model (SSM) approach. With switched SSMs it is possible to directly incorporate element mismatches and parasitics from the design into the model. This provides greater flexibility to designers of data converters. The results of the proposed model are compared to transistor level simulations of the real design in the frequency domain. The achieved speedup factor is > 1000
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Full text linkWe 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
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