1,720,960 research outputs found
Ultra-compact pseudoelliptic waveguide filters using TM dual-mode dielectric resonators
No full textThis paper presents a solution for ultra-compact pseudoelliptic dual-mode filters using high permittivity dielectric resonators. The basic idea consists of using a pair of degenerate resonant TM modes within a cavity loaded with a very high-permittivity puck. Nonresonating modes, instead, are exploited so as to produce a direct coupling between the input and the output of the dielectric-loaded cavity. In this way, a single cavity can provide two transmission poles and zeros, thus leading to N-pole and N-zero filters. The proposed configuration yields very compact and geometrically simple structures with resonator unloaded Q around 3000 at C-band. The geometrical dimensions of a 4-pole and 4-zero waveguide filter for C-band applications are 32×32×20 mm3 (using εr=34). Its FBW is 2.4% and the in-band IL is 0.3 dB by HFSS® simulations. The first prototype of the 4th order filter is going to be fabricated
Ultra-compact filters using TM dual-mode dielectric-loaded cavities with asymmetric transmission zeros
No full textThis paper presents ultra-compact dual-mode dielectric-loaded waveguide bandpass filters with Nth-order pseudoelliptic filtering function and asymmetric positioning of N transmission zeros. A waveguide cavity is loaded with a very high-permittivity rod (εr>30). Two degenerate resonant TM modes are employed along with nonresonating modes. In contrast to previous works, that are limited to structures with a symmetric response, in the proposed solution both modes are directly coupled to the input and output interconnections. Nonresonating modes are exploited to produce a direct source-load coupling. In this way, a single cavity generates two transmission poles and two transmission zeros located either below or above the two poles, thus realising a basic building block for N-pole and N-zero filters with asymmetric response. The dimensions of a 3% FBW 4th-order filter with 4 zeros at 4.35 GHz are 40×40×12 mm3 (using εr=34). A preliminary prototype has been fabricated and measured showing an unloaded Q of 1750 and good agreement with HFSS® simulations
MEMS-based LC tank with extended tuning range for low phase-noise VCO
No full textThis paper presents the modeling, manufacturing, and testing of a micro-electromechanical system (MEMS)-based LC tank resonator suitable for low phase-noise voltage-controlled oscillators (VCOs). The device is based on a variable MEMS varactor in series with an inductive coplanar waveguide line. Two additional parallel stubs controlled by two ohmic MEMS switches have been introduced in order to increase the resonator tunability. The device was fabricated using the FBK-irst MEMS process on high resistivity (HR) silicon substrate. Samples were manufactured with and without a 0-level quartz cap. The radio frequency characterization of the devices without 0-level cap has shown a continuous tuning range of 11.7% and a quality factor in the range of 33-38. The repeatability was also tested on four samples and the continuous tuning is 11.7 ± 2%. Experimental results on the device with a 0-level cap, show a frequency downshift of about 200 MHz and a degradation of the quality factor of about 20%. This is, most likely, due to the polymeric sealing ring as well as to a contamination of the ohmic contacts introduced by the capping procedure. A preliminary design of a MEMS-based VCO was performed using Advanced Design System and a hardwired prototype was fabricated on Surface Mount Technology on RO4350 laminate. The prototype was tested resulting in a resonance frequency of 5 GHz with a phase noise of -105 and -126 dBc at 100 KHz and 1 MHz, respectively, and a measured output power of -1 dBm. © 2015 Cambridge University Press and the European Microwave Association
MEMS-based LC tank with extended tuning range for low phase-noise VCO
No full textThis paper presents the modeling, manufacturing, and testing of a micro-electromechanical system (MEMS)-based LC tank resonator
suitable for low phase-noise voltage-controlled oscillators (VCOs). The device is based on a variable MEMS varactor in
series with an inductive coplanar waveguide line. Two additional parallel stubs controlled by two ohmic MEMS switches have
been introduced in order to increase the resonator tunability. The device was fabricated using the FBK-irst MEMS process on
high resistivity (HR) silicon substrate. Samples were manufactured with and without a 0-level quartz cap. The radio frequency
characterization of the devices without 0-level cap has shown a continuous tuning range of 11.7% and a quality factor in the
range of 33–38. The repeatability was also tested on four samples and the continuous tuning is 11.7+2%. Experimental
results on the device with a 0-level cap, show a frequency downshift of about 200 MHz and a degradation of the quality factor
of about 20%. This is,most likely, due to the polymeric sealing ring as well as to a contamination of the ohmic contacts introduced
by the capping procedure.Apreliminary design of aMEMS-basedVCOwas performed usingAdvancedDesign Systemand a hardwired
prototype was fabricated on Surface Mount Technology on RO4350 laminate. The prototype was tested resulting in a resonance
frequency of 5 GHz with a phase noise of 2105 and 2126 dBc at 100 KHz and 1 MHz, respectively, and a measured
output power of 21 dBm
Design and manufacturing of X-Band tunable microcavity resonator in MEMS technology
Full text linkThis paper presents the design modeling and
hardwire prototypes fabrication of a X-band tunable cavity
resonator based on MEMS technology. Brass metallic
cavities with inner post have been thermo-compressive
bonded on a silicon substrates having 4 MEMS varactors
based on toggle mechanism. The tunable resonator was
simulated in ANSYS® HFSS full wave environment,
resulting in a continuous tuning range of 22% with an
unloaded quality factor (Q) in the range of 80-180 and a
very small volume of 3.2x3.2x1.4 mm3. Preliminary
experimental results are presented. The measurements on
hardwired prototypes result in a maximum unloaded
quality factor (Q) of 80 and tuning range of 14%, centered
at the frequency of about 9GHz. The main responsible of the
lower measured quality factor, respect to the simulated one,
was found to be the additional losses in the silicon substrate
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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