1,720,970 research outputs found
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
D-Band RX Front-End With a 0 –360 Phase Shifter Based on Programmable Passive Networks in SiGe-BiCMOS
No full textActive phased arrays are key enablers for high-capacity wireless links and imaging sensors at millimeter wave, but require advanced front-end circuits. On the receiver side, the front-end comprises a low-noise amplifier (LNA) followed by a programmable phase shifter (PS), required to adjust the phase of each channel before performing the coherent summation of the signals captured by different antenna elements. In D-band, conventional PSs based on the vector interpolation principle limit the dynamic range with a noise or linearity penalty due to transistors operating close to max, in currently available silicon technologies. This work presents a front-end where the variable phase shift is achieved using passive structures, with a noise figure equal to the insertion loss (IL) but inherently linear. Different passive networks providing a programmable phase shift in fine and coarse steps are developed and interleaved with active gain stages to build a 0 –360 PS. Cascode structures are used as gain stages, in the PS and in the preceding LNA, and reactive feedback is introduced around the common-emitter (CE) device to boost the gain. A D-band receiver front-end is implemented in BiCMOS 55-nm technology. With a power consumption of 80 mW from a 2 V supply, measurements prove 20 dB average gain, 130–170 GHz operating frequency with 0 –360 phase shift control, and average NF and of 7 dB and 2 dBm, respectively. Normalizing the dynamic range to power consumption, the achieved results compare favorably against state-of-the-art
AM-AM and AM-PM Distortion in D-Band BiCMOS Vector-Interpolation Phase Shifters
No full textSub-THz phased-array transceivers need phase shifters for a coherent combination of the transmitted and received signals. Vector-interpolation phase shifters demonstrate wide bandwidth, low loss, and compact footprint, but may suffer from poor linearity, restrained by the need of high dynamic range variable gain amplifiers (VGAs). This article investigates the role of VGA impairments in a vector-interpolation phase shifter, with primary focus on the AM-AM and AM-PM distortions. Then, three common VGA structures are analyzed and compared, revealing a best candidate to optimize linearity. A single-ended input/output phase shifter is finally implemented in 55 nm SiGe BiCMOS technology. The test chip allows experimental validation of the theoretical results by using the VGAs in different operating modes. It is also shown that, in a single-ended phase shifter, the common-mode current generated by the VGAs may compromise gain and linearity. Solutions to the problem are introduced in the design, including a novel current-mode balun that provides large (4:1) impedance transformation and high common-mode rejection with equal primary and secondary inductors. Experimental results prove wideband operation, from 130 to 175 GHz, with 3.5 dB gain. The phase shift is programmable in 10° steps with rms phase and amplitude errors across frequency < 5° and < 0.8 dB, respectively. With the optimal VGA operation mode, the output power at 1 dB gain compression (OP1dB) is above 1.8 dBm with < 10° AM-PM distortion. Experiments compare favorably against previous works in the same band and in similar technologies
A 20mW 130-175GHz Phase Shifter with Meandered λ/2 TLINEs in BiCMOS 55nm
No full textThis paper presents a compact and low-power D-Band four-quadrant active phase shifter using meandered λ/2 transmission-lines (TLINEs) for phase inversion. TLINE impairments (loss and phase deviation from 180°) are analyzed and their effects on the output vector space are discussed. A calibration technique is applied such that the phase shifter RMS amplitude and phase errors are kept under 1.2dB and 8°, respectively. Implemented in SiGe BiCMOS 55 nm, the proposed circuit covers 130- 175 GHz bandwidth with -4.5dB peak gain, O P 1 d B greater than -3dBm and 20mW average power consumption
A D-Band Low-Noise-Amplifier in SiGe BiCMOS with Broadband Multi-Resonance Matching Networks
No full textSilicon amplifiers in D-Band are required to operate at high gain-bandwidth products and close to the cutoff frequency f_\max . Multi-stage amplifiers commonly employ stagger-Tuning to meet the desired bandwidth, but with sub-optimal noise and linearity. Better performance is achieved with broadband inter-stage matching and gain progressively distributed among the stages. This work proposes a design flow for broadband matching networks approximating the response of a doubly-Tuned transformer. The technique is applied to design a 3-stage D-band LNA in BiCMOS 55 nm technology. Measurements show 28 dB gain, 127-168 GHz bandwidth, NF down to 5.2 dB and >2dBm output compression point with 30 mA DC current from 2V supply. The performance compare favorably against previous works
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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