1,720,973 research outputs found
A New Approach to Microwave Power Amplifier Design Based on the Experimental Characterization of the Intrinsic Electron-Device Load-line
No full textThis paper presents a new original approach to power amplifier design, which is mainly based on low-frequency nonlinear empirical electron device (ED) characterization. The proposed technique enables the same level of accuracy provided by expensive load-pull measurement systems to be obtained through a relatively simple and low-cost setup. Moreover, ED currents and voltages related to reliability issues can be directly monitored. Different experimental examples based on power GaAs and GaN field-effect transistors are provided to demonstrate the validity of the proposed approach
An X-to-Ka band MMIC up-converter in GaAs pHEMT technology for Ka-band broadband satellite communications
No full textIn this article, an X-band to Ka-band up-converter circuit designed for the transmitting chain of Satcom-on-the-move terminals is presented. The circuit is implemented using a 0.25 μm GaAs pHEMT microwave monolithic integrated circuit commercial process. It operates at fixed LO frequency of 22 GHz, IF input frequency within the band (8-9) GHz and corresponding RF output frequency within (30-31) GHz band. The up-converter circuit is composed of a resistive FET mixer, a K-band LO buffer amplifier, and a Ka-band medium power amplifier at the RF output. The bias operating condition of the entire multifunction chip is Vdd?=?2.8 V, Idq?=?322 mA, for a power consumption of 900 mW, when the Ka-band high power amplifier (HPA) operates in linear conditions. The chip dimensions are 3.4 × 2.8 mm2. The up-converter provides more than 12 dB conversion gain over the full bandwidth, when operated with LO input power of 0 dBm and IF fixed input power of -5 dBm. It also achieves 25 dBc of LO isolation at the RF output port. The high 1 dB compression point P1dB?>?19 dBm, along with an OTOI in excess of 29 dBm, make the circuit suitable to directly drive Ka-band high power amplifiers in very linear operating conditions
X-Band GaN Power Amplifier for Future Generation SAR Systems
No full textA X-band GaN monolithic microwave integrated circuits (MMIC) High Power Amplifier (HPA) suitable for future generation Synthetic Aperture Radar systems is presented. The HPA delivers 14 W of output power, more than 38% of PAE in the frequency bandwidth from 8.8 to 10.4 GHz. Its linear gain is greater than 25 dB. For the first time an MMIC X-band HPA has been designed by directly measuring the transistor behavior at the current generator plane. In particular, optimum device load-line has been selected according to the chosen performance tradeoffs
Class-A Power Amplifier Design Technique Based on Electron Device Low-Frequency Characterization
No full textIn this paper, a new approach to class-A power amplifier design is proposed. Such a technique, which is mostly based on low-frequency characterisation, allows to reach the same design goals obtained through expensive nonlinear setups operating at microwave frequencies. In order to demonstrate the effectiveness of the proposed design technique, a practical example of class-A power amplifier design, based on GaN technology, is deeply investigated
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
High-efficiency broadband power amplifier design technique based on a measured-load-line approach
No full textThe paper presents an innovative power amplifier design technique oriented to microwave applications which require both high efficiency and large bandwidth. The approach is based on a recently proposed technique which, by exploiting a direct low-frequency nonlinear electron device characterization in conjunction with a model-based description of the device capacitances, achieves the same level of accuracy provided by expensive nonlinear setups operating at microwave frequencies. As a tough test-bench, a commercially available discrete power GaN FET has been adopted
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
“Hybrid” approach to microwave power amplifier design
No full textA new “hybrid” approach to microwave power amplifier design is presented which is based both on experimental large-signal low-frequency I/V load-line characterization and a model-based description of the device capacitances. Such a technique allows to get the same information obtained through nonlinear measurement setups operating at microwave frequencies. Several simulated and experimental data are proposed, based on GaN technology, in order to prove the effectiveness of the methodology
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
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