1,720,952 research outputs found
A highly linear downconverter for on-chip linearization of digital power amplifiers
No full textThis work presents a highly linear quadrature down-converter topology intended for the linearization of digital Transmitters(DTX). By integrating it with a DTX, a fully integrated on-chip output-signal correction loop comes closer to its realization. The proposed down conversion architecture can measure the errors introduced by the non-linearity of the transmitter, rather than the transmitter output itself. These errors are determined by comparing the downconverted transmitter output signals with its analog ideal baseband I and Q reference signals. The reference signals are provided by low-power digital-to-analog converters(DACs), using the same IQ data input as the power DTX. This approach reduces the resolution/dynamic range requirements on the trans-impedance-amplifier (TIA) and analog-to-digital converters(ADCs) since the error signals have a reduced dynamic range compared to the transmitter’s output signal itself. These lower requirements on the ADCs and elimination of off-chip couplers and filter sease the integration of a complete digital pre-distortion (DPD) correction loop in future DTX implementations. As the core of this thesis work, a linear harmonic rejection mixer was designed. It uses resistors inits mixer branches to implement the proper currenct scaling needed for harmonic rejection (HR). The resulting HR mixer avoids the unwanted down-conversion of the higher harmonics of the DTX to the base band frequencies of interest. Also, atrans-impedance amplifier was designed with the proposed passive mixer. These TIAs are based on an inverter topology for maximum tranconductance and were biased for optimal linearity and offered a bandwidth over 1.8GHz. The proposed DTX error-detection architectureis implemented in the current domain. Performing the subtraction before the TIA drastically reduces the voltage swing at the input of the TIA, benefiting the linearity of the mixer and reference DAC. The overall HR-mixer configuration is simulated for its linearity, yielding an IIP3 of 49dBm, which to the best of the author’s knowledge, is the best-reported linearity for high bandwidth down-converting applications.Electrical Engineerin
Acceleratie van beeldverwerking met de ?-VEX VLIW-processor
No full textDeze scriptie betreft een onderzoek naar het versnellen van een JPEG-decoder in een embedded systeem. Hierbij wordt de ?-VEX VLIW-processor als accelerator gebruikt. Onderzocht wordt hoe de hardware en software aan elkaar kunnen worden aangepast om de applicatie zo snel mogelijk uit te voeren.Computer EngineeringMicroelectronics & Computer EngineeringElectrical Engineering, Mathematics and Computer Scienc
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
A Load Insensitive Doherty Power Amplifier with better than −39dBc ACLR on 2:1 VSWR Circle using a Constant 50 Ω Trained Pre-distorted Signal
No full textThis paper presents a low-loss load-insensitive Doherty power amplifier (DPA) technique. The proposed DPA is insensitive to ohmic load variation by adjusting its supply voltages and input drive of the main and peaking stages in a mirrored approach. Moreover, a low-loss tunable matching network (TMN) is employed to cancel out any reactive part of the load. To validate this technique, a printed circuit board (PCB) based demonstrator consisting of the Doherty PA, a six-port reflectometer, and a tunable shunt resonator have been fabricated. When subjected to a 50 Ω load, at the 1 dB compression point, the DPA delivers an output power of 32.3 dBm with a power gain and peak drain efficiency of 14.6 dB and 61 %, respectively. When the DPA is driven with a pre-distorted 64-QAM 4 MHz signal optimized for the 50 Ω loading condition, it delivers 24.4 dBm at 41 % average drain efficiency, with EVM/ACLR −40.9 dB / −46.9 dBc. Subsequently, when subjected to a 2:1 VSWR over a 0°−360° mismatch trajectory, using the unaltered 50 Ω DPD correction, it is capable of delivering an output power of 24.4 ± 0.1 dBm with a 34–39 % drain efficiency while maintaining an EVM/ACLR better than −32.3 dB / −39.3 dBc for all load conditions.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Electronic
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
A Four-Way Series Doherty Digital Polar Transmitter at mm-Wave Frequencies
No full textThis article presents an efficient digital polar transmitter (DPTX) at mm-wave frequencies that exploit a novel N -way series Doherty combiner (SDC) to enhance its drain and system efficiency at deep power back-off (PBO). The proposed N -way SDC is scalable and can be implemented elegantly using N transformers and N-1 shunt capacitors. As a proof of concept, a four-way Doherty DPTX is realized with the proposed SDC in which four identical but independent digital phase modulators deliver a phase-modulated constant envelope signal to their corresponding digital power amplifiers to perform the required amplitude modulation. Fabricated in a 40nm CMOS process, the proposed DPTX occupies a core area of 1.1 mathrm {mm^{2}} and exhibits 18.7dBm saturated output power and <-40dBc LO feedthrough. It demonstrates a drain efficiency of 33%/36%/22% at 0/4.5/11.5dB PBO at a 29.5GHz carrier frequency. While transmitting a 300MHz 64-QAM OFDM signal with a peak-to-average power ratio of 10.7dB, the DPTX achieves 18%/8% average drain/system efficiency, -27.6dB error vector magnitude, and -27.5dBc adjacent channel leakage ratio. To the best of our knowledge, this work is the first reported mm-wave Doherty transmitter that includes the entire chain all the way from the binary data stream up to the modulated mm-wave output signal.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Electronic
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