1,721,058 research outputs found
Circuiti e sottosistemi a microonde e onde millimetriche per ricevitori a basso rumore e antenne intelligenti
Full text linkQuesto lavoro affronta gli aspetti riguardanti le metodologie e tecniche di analisi e progettazione per alcune funzionalità in front-end ricevitori a radiofrequenza ad elevata sensibilità e riconfigurabili. Tali funzionalità sono: l’amplificazione a basso rumore e il controllo dell’ampiezza di un segnale a RF. Infine, un’ulteriore investigazione ha focalizzato gli aspetti e le criticità in circuiti multi-funzione a elevata integrazione.
E’ stata mostrata una metodologia per progettazione di amplificatori a basso rumore a microonde che ha portato a definire le relazioni di adattamento simultaneamente ottenibile in ingresso e uscita in un LNA. Il principale risultato di tale investigazione è l’individuazione di un grafico che permette di valutare in modo sinottico il guadagno di trasduzione e gli adattamenti I/O di una rete 2-porte amplificatrice una volta fissata l’impedenza di sorgente, e quindi il fattore di rumore del LNA.
Sull’argomento degli amplificatori a basso rumore a onde millimetriche, è stato proposto un insieme di metodi analitici e sintetici che coprono le tematiche dalla scelta della tecnologia del dispositivo attivo al test del LNA realizzato. E’ stato ripreso il significato della Misura di Rumore nella progettazione a basso rumore a onde millimetriche investigando anche le tematiche della simulazione EM planare e 3D a onde millimetriche.
All’interno della tematica sul controllo dell’ampiezza di un segnale a RF è stato investigato in profondità lo sfasamento parassita connesso al cambio di stato in attenuatori digitali a commutazione. E’ stata suggerita una tecnica circuitale e sono state ricavate equazioni di progetto che permettono di compensare tale sfasamento indesiderato, fornendo una relazione che consente di dimensionare l’elemento reattivo che compensa tale effetto sgradito.
Infine, sulla materia della progettazione di circuiti-multi funzione a elevata integrazione è stata investigata la realizzabilità di un modulo contenente diverse funzionalità: controllo dell’ampiezza del segnale, amplificazione, scelta del modo T/R, controllo della fase del segnale e conversione seriale/parallelo dei dati di comando. Sono state presentate le procedure di progetto di alcuni sottosistemi nonché i criteri e i passi seguiti nella fase di integrazione.This work deals with aspects relating to analysis and design methodologies and techniques for some circuits in high sensitivity and reconfigurable front-end RF receivers. These circuits are: low noise amplifier and RF attenuators. Finally, further investigation has focused aspects and issues of multi-function high integration circuits.
A methodology for designing microwave low noise amplifiers is reported. The latter has led to define the I/O matching relationships simultaneously achievable in an LNA. The main result of this investigation is the identification of a chart that allows to synoptically evaluating the achievable gain and I/O matching of a 2-port amplifier, once the source impedance is fixed and consequently the LNA noise factor.
A set of analytical and synthetic methods on millimetre wave low noise amplifiers has been proposed, covering topics from the active device technology selection to test the realized LNA. The meaning of the noise measure parameter is reprised for designing millimetre wave low-noise. The issues of and 3D planar EM millimetre wave simulation is also investigated.
The parasitic phase shift in digital attenuators has been investigated in depth. Such parasitic effect is related to the change of state in digital switched attenuators. A technique has been suggested and circuit equations were derived that allow to compensate such unwanted phase shift, providing design relations that allows to estimate the value of the reactive element that compensates for this undesirable effect.
Finally, in the field of multi-function high-integration circuits design, the feasibility of a module containing several functionalities has been investigated. The latter are: control of the signal amplitude, amplification, selection of Tx/Rx mode, control the phase of the signal and serial to parallel control data conversion. The design procedures of some sub-modules, together with the criteria and the steps followed in the process of integration, have been reported
Feasibility study and design of a robust low-noise amplifier operating at millimeter-wave for high reliability applications
Full text linkA feasibility study and the corresponding design flow for robust millimeter wave GaN LNAs is provided in this paper. Particular attention is devoted to the selection of the optimum geometry of the first stage active device. A trade-off is shown between noise performance and robustness requirements. The beneficial effects of source degenerative feedback are shown. The LNA's simulated performance are gain > 20B, NF < 1.7dB and power handling capability verified up to +20 dBm input power in CW operation. This design is well suited for operation in high reliability systems, such as space operation on airborne applications
Improved microwave attenuator topology minimizing the number of control voltages
No full textThis letter presents an improved circuit topology to minimize the number of external control voltages that are required to set the state of an N-bit microwave digital attenuator. An alternative method to connect the control signal is proposed. Typically, the control signal is connected to the gate terminal of the field effect transistor while the source terminal is DC grounded. Here, the control signal is applied to the source terminal of the field effect transistor while the gate is connected to a fixed reference voltage. In this way, only one control voltage is necessary to set the state of single attenuator cell vs two control voltages required in the typical case. The proposed method becomes particularly beneficial as the number of bits increases (ie, >4). The topology has been validated through design, realization, and testing of a 5-bit Monolithic Microwave Integrated Circuit (MMIC) attenuator operating over the full C-band (4-8 GHz)
Design of a 5W Single Chip Front-End for C-Ku Band T/R Modules
No full textIn this contribution an integrated Single Chip Front-End (SCFE) for next generation Electronic Warfare T/R modules is presented. The proposed circuit relies on a concurrent design technique merging switches and HPA matching network. Realized MMIC features a 6.3×4.3mm 2 outline operating in the 5.5-18 GHz band with a typical output power of 6W, an associated PAE of 10% and 3dB insertion loss in Rx mode
Design of a MMIC low-noise amplifier in industrial gallium arsenide technology for E-band 5G transceivers
No full textThe technology, design procedure and measurements of an E-band (71-86 GHz) high performance gallium arsenide (GaAs) low-noise amplifier (LNA) are presented. The latter provides a gain in excess of 20 dB, an average in-band noise figure (NF) of 2.3 dB, absorbing 60 mW DC bias power. A European space-qualified technology (OMMIC's GaAs 70 nm process) has been selected to demonstrate the feasibility of employing the proposed LNA for production-ready wireless backhaul point-to-point communication systems. A possible installation scenario has been depicted, in order to verify the maximum distance at which TX and RX antennas can be placed and employing the proposed LNA as first amplifying stage of the receiver chain
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
Compact wideband downconverter module for electronic warfare applications
No full textAnalysis and design of a compact wideband downconverter module for EW applications are presented in this paper. Architectural and circuit solutions trade-offs are described and related to the module's electrical and mechanical requirements and the key components characteristics. RF chain simulations and their comparison with measurements of the manufactured module are finally illustrated
- …
