1,720,971 research outputs found
IF Amplifier Section in 90nm CMOS Technology for SoC Microwave Radiometers
No full textIn this paper a novel design solution in 90nm CMOS technology is proposed for the IF amplifier, low-pass filter and square-law power detector of a system-on-chip (SoC) microwave radiometer. To minimize the number of off-chip components (just a single capacitor) the IF filter is based on an active gmC configuration, whereas the power detector exploits the MOS transistor non-linearity, i.e., avoiding the need for Schottky diodes. The fabricated IF chip features a sensitivity of 3mV/nW, a linearity range of about 25dB around the -60dBm level, a noise equivalent bandwidth of 58MHz and a current consumption of only 1.8mA at 1.2V supply. The core area is within a rectangle of 220um per 540um. The proposed design solution is also compatible with SiGe BiCMOS processes and can be regarded as a further step toward the realization of microwave radiometric sensors fully integrated on silicon
Avalanche Microwave Noise Sources in Commercial 90-nm CMOS Technology
No full textThis paper presents a microwave noise source implemented in a commercial CMOS technology. The circuit is based on the avalanche noise generated by both the source-to-bulk and the drain-to-bulk junctions in reverse breakdown. Two sources of different junction area are fabricated using a standard NMOS transistor in 90-nm CMOS technology having a width of 5- and 20-μm, respectively. From the experimental characterization emerges that the breakdown voltage of the source/drain to bulk diodes is 12.4 V, whereas excess noise ratios (ENRs) of 20 dB (5-μm source) and of 25 dB (20-μm source) are observed at 24 GHz for a current density of about 0.14 mA per square micrometer. Finally, a theoretical explanation of the observed behaviors is proposed by means of an equivalent circuit. The developed noise source can be used in a CMOS system-on-chip (SoC) for a variety of applications ranging from the built-in self test (BIST) of the RF chain to the calibration of fully integrated microwave radiometric sensor
A Low-Cost Microwave Radiometer for the Detection of Fire in Forest Environments
No full textThis paper deals with the development of a microwave noise-adding radiometer, which is purposely designed for the fire detection in forest environments. The sensor operates at 12.65GHz and exploits commercial Satellite Television (SAT-TV) components such as a parabolic dish and a low-noise block. First, a simple system model is presented to estimate the radiometric contrast due to the presence of fire (increase in the antenna noise temperature with respect to the background) at a certain distance from the receiving antenna. Then, the design of the sensor is addressed, underlining the key technologies that allow the required performance to be attained at low industrial costs. An experimental characterization of the developed radiometer is reported focusing on both accuracy and sensitivity issues. Due to a continuous gain calibration based on the noise-adding procedure, the antenna noise temperature can be retrieved with an absolute error of 4K without any thermal stabilization of the instrument electronics. Last, real fire detection experiments have been carried out both in laboratory and open-space environments. A radiometric contrast of 8.8K has been recorded for a wooden fire of 0.2 square meters active area placed at a distance of about 30m from the antenna
Development of Low-Cost 24 GHz Circuits Exploiting System-in-Package (SiP) Approach on Commercial PCB Technology
No full textThis paper deals with 24-GHz circuits developed by exploiting a system-in-package approach. In order to reduce the cost as much as possible, a standard multilayer printed circuit board (PCB) technology has been adopted. Such a circuit consists of a package built utilizing a 0.3-mm thick fiber-glass substrate with 3.38 relative permittivity. The contacts between the substrate and the mother board are realized along the package perimeter exploiting 0.6-mm via-hole metalization and half halo shield soldering pad. First, the developed package is simulated and optimized by means of commercial electromagnetic software. Then a prototype is fabricated and measured. The obtained results show that the whole frequency band from DC to 30 GHz can be covered. A packaged 26.5-mm straight microstrip line exhibits an |S11| value better than -12 dB and an |S21| value of about -1.4 dB at 24 GHz. This value is only 0.6-dB worse than that of the unpackaged line. A single-balanced diode mixer and a low-noise amplifier (LNA) for industrial, scientific, and medical applications are then designed. The integration of these building blocks within the PCB package is finally demonstrated and experimentally verified. The packaged mixer shows a 6.8-dB conversion loss. The packaged LNA, instead, features a 9.1-dB gain with a 3.4-dB noise figure
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Avalanche noise diodes: A compact circuit model compatible with advanced CAD tools
No full textThis paper proposes, for the first time, a compact model for avalanche noise diodes that can easily be inserted in advanced CAD tools. The model is based on the theory of the Read type microwave avalanche diodes. It fully accounts for the electronic tuning of the avalanche frequency with the square root of the diode biasing current and is scalable with the device area. The equivalent circuit has been written for ADS of Keysight Technologies and is verified against published experiments. The modeled input impedance is within 20% of the measured one in the whole frequency band from DC to 40 GHz. Futhermore, the Excess Noise Ratio (ENR) of the diode can be predicted as a funtion of the avalanche current and is in good agreement with experiments. The developed model is useful for the simulation and the design of calibration circuits adopted by microwave radiometers, radio astronomy receivers and high reliability wireless apparatuses.ESPLABICLA
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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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