1,720,956 research outputs found
Time-to-Digital Converter for Frequency Synthesis based on a Digital Bang-Bang DLL
No full textThis paper presents the design of a time-digital
converter suitable for a 3.5-GHz all-digital phase-lock loop. The
converter is based on a digital bang-bang delay-lock loop, which
allows constant resolution over process and temperatures spreads, avoids an off-chip filter and guarantees fast lock. The clock rate of the digital filter is scaled down by 8 from the 3.5-GHz input to allow its implementation with standard cells. The occurrence of a limit cycle is analytically predicted and properly minimized, and its effect on the PLL phase noise is discussed. The circuit fabricated in 90-nm CMOS entails 16 delay stages, which lock to the input frequency in the 2.9-3.9-GHz range (limited by the available signal source). The delay of each TDC cell can be controlled with 50-fs step and the TDC time resolution is 16 ps at 3.9GHz. The power consumption ranges between 8.1 and 16.5 mW. The limit-cycle-induced spur is below -50 dBc
Analysis and characterization of pre-diffusion in multi-linear silicon drift detectors
No full textMulti-Linear Silicon Drift Detectors (MLSDD) are silicon detectors in which signal electrons are confined within parallel drifting columns at few micrometers from the anodes’ surface and transported towards point-like anodes by an electrostatic field. During the initial motion across the thickness the signal electrons spread in all directions to a given width—we call this phenomenon pre-diffusion—until the signal electrons are focused in the drift channels which suppress any further spread into adjacent channels. This work is devoted to the study of the initial motion of the electron cloud when the electrons are being focused toward the minimum of the potential energy. We developed an analytical model to predict the initial charge spread and carried out a detailed measurement campaign to evaluate the impact of the detector operating conditions and of the charge injection level on the initial charge spread. The design of the electron spread
during pre-diffusion allows optimization of MLSDD for different applications
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
AD-PLL for WiMAX with Digitally-Regulated TDC and Glitch Correction Logic
No full textThis paper describes the design of an All-Digital Phase Locked Loop (AD-PLL) for wireless applications in the WiMAX 3.3–3.8 GHz bandwidth. The time/digital converter (TDC) sets the in-band noise and it may be responsible for the presence of spurious tones at the PLL output. The TDC is implemented as a delay-locked loop (DLL) to be insensitive to process spreads and it uses a lead-lag phase detector and a digital loop filter to further take advantage of the digital approach. The most important source of spurs is identified in the time skew between counter and TDC in the PLL. This mechanism gives rise to a glitch in the digital feedback signal and spurs in the output spectrum. A simple glitch-corrector logic is described, that completely removes this effect, thus allowing to meet the phase noise specifications. The AD-PLL has been designed in a 90 nm CMOS process
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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