1,720,958 research outputs found
Analysis and design of CMOS and bipolar SiGe:C integrated circuits for low power RF receivers and radar applications
Get PDFThis dissertation proposes the analysis and the design of two radio-frequency integrated circuits.
In the first part a low-power wireless receiver front-end for Wireless Sensor Networks is developed. The circuit comprises a Low-Noise Amplifier, Voltage Controlled Oscillators and Mixers, building a complete single-stage quadrature receiver front-end for low-power applications. The compact architecture based on a current reuse topology is described and motivated; an in-depth time-variant analysis is performed to optimize the circuit; a test 2.4GHz receiver is finally designed and realized in a cheap 90nm CMOS technology with a 3μm thick top metal for high-quality integrated inductors. Measurement results confirm the correctness of our analysis and the validity of the proposed circuit architecture.
In the second part of this dissertation a X-band upconverter for a Frequency-Modulated Continuous-Wave radar system is developed. The goal of the project is that of developing a wideband upconverter with a clean output spectrum and low phase noise. The proposed architecture is constituted by two mixers, baseband interfaces, a pre-power amplifier and the on-chip circuitry to generate quadrature local oscillator signals from an external reference local oscillator. Several mechanisms which lead to spurious tones at the output are discussed, with emphasis on the design issues related to the image-rejection, the mismatches and the nonlinearities in the large-signal baseband interface.
Two versions of the modulator are designed and compared: a) a CMOS version built in a 65nm digital technology based on a zero DC current passive mixer for minimum flicker noise and b) a bipolar version built in a 0.35μm SiGe:C technology based on an active Gilbert mixerQuesta tesi di dottorato propone l'analisi e la progettazione di due circuiti integrati a radio-frequenza.
Nella prima parte del lavoro viene sviluppato il front-end di un ricevitore wireless a basso consumo di potenza per Wireless Sensor Networks. Il circuito, che comprende un amplificatore a basso rumore, oscillatori locali e mixer, costituisce un sistema di ricezione completo implementato in un singolo stadio per ridurre il consumo di potenza.
L'architettura proposta, basata sulla tecnica del riutilizzo della corrente di polarizzazione, viene motivata e descritta in dettaglio; segue un'accurata analisi tempo-variante dell'architettura per l'ottimizzazione del circuito proposto; il ricevitore a 2.4GHz è stato infine realizzato con una tecnologia CMOS digitale a 90nm con top metal ottimizzato per la realizzazione di induttori integrati con alto fattore di qualità. Le misure effettute sui campioni confermano la correttezza della nostra analisi e la validità dell'architettura proposta.
Nella seconda parte di questa tesi di dottorato viene sviluppato un upconverter per un Frequency-Modulated Continuous-Wave radar in banda X. L'obiettivo del progetto è quello di realizzare un upconverter a banda larga, con uno spettro in uscita libero da toni spuri e con minimo phase noise. L'architettura proposta comprende due mixer con relative interfacce in banda base, un amplificatore a radiofrequenza e tutta la circuiteria per la generazione dei segnali in quadratura per pilotare i mixer a partire da un oscillatore locale esterno di riferimento.
Vengono analizzati vari meccanismi di generazione di toni spuri all'uscita, con particolare enfasi sui problemi legati alla reiezione dell'immagine, ai mismatches ed alle nonlinearità generate nell'interfaccia in banda base.
Due versioni del modulatore sono state progettate e confrontate: a) una versione realizzata in una tecnologia CMOS a 65nm digitale basata su un mixer passivo a corrente di polarizzazione nulla per minimizzare la generazione di rumore flicker e b) una versione realizzata in una tecnologia bipolare SiGe:C a 0.35μm basata su un mixer di Gilbert attiv
A X-Band I/Q Upconverter in 65 nm CMOS for High Resolution FMCW Radars
No full textThis work presents a CMOS X-band I/Q upconverter for a FMCW radar system. The use of passive current mixers allows to address the main drawbacks of CMOS technology, namely flicker noise and reduced linearity due to low supply voltage, paving the way to monolithic integration with digital intensive baseband circuitry. Prototypes were built in a 65 nm digital technology, showing a peak output power of -3.4 dBm at 10.6 GHz with a corresponding HD3 lower than -40 dBc and an image rejection greater than 41 dB across the 9.5-12 GHz LO band, while adding negligible phase noise to the output signal. The circuit occupies an area of 0.91 mm(2) and consumes 192 mW
Accurate time-variant analysis of a current-reuse 2.2 GHz 1.3 mW CMOS front-end
No full textThis paper presents a 2.2 GHz receiver front-end capable of an extreme current reuse, where the low-noise amplifier, the quadrature mixers and VCOs only draw 1.3 mA from a 1V supply. A careful time-variant analysis is carried out, resulting in a very accurate expression of the conversion gain and bandwidth of the downconverter. A prototype, implemented in a 90 nm CMOS technology, shows 27 dB gain over a 14 MHz bandwidth, with a noise figure of 13 dB. The input-referred 1 dB compression point is -23.7 dBm
Design of broadband inductorless LNAs in ultra-scaled CMOS technologies
No full textShunt-shunt resistive feedback is used in this paper to design inductorless broadband LNAs in a digital 45 nm CMOS technology. Simulation results show 18 dB gain over a 10 GHz bandwidth, with NF -7 dBm in-band, while consuming 32 mW from a 1 V supply voltage
Time-variant analysis and design of a power efficient ISM-band quadrature receiver
No full textIn this work a 2.2 GHz quadrature receiver
front-end suitable for low-power applications is presented.
The low-noise amplifier, the mixer and the voltage-controlled
oscillator are merged into a single stage, making the
circuit capable of extreme current reuse while keeping it
still functional at low supply voltage. A careful linear timevariant
analysis is proven to be necessary to accurately
predict the conversion gain and the bandwidth of the
downconverter. A prototype, implemented in a 90 nm
CMOS technology, validates the theoretical analysis,
showing 27 dB of downconversion gain over a 14 MHz
base-band bandwidth; the noise figure is 13 dB with a
flicker corner frequency of 200 kHz; the input-referred
1 dB compression point is -23.7 dBm. The circuit draws
only 1.3 mA from a 1.0 V supply
Analysis and Design of a Low-Power Single-Stage CMOS Wireless Receiver
No full textThe thorough analysis and the design of a complete 2.2 GHz quadrature receiver front-end suited for low-power applications is reported in this work. The circuit, built in a 90 nm CMOS process, features a stacked single-ended low-noise amplifier and a self-oscillating mixer. The oscillator LC tank is designed to provide gain at low frequency without decreasing the quality factor at the oscillating frequency. A careful analysis shows that the parasitic capacitances at the output nodes ultimately limit the achievable conversion gain. Measurements show a conversion gain of 27.1 dB with a 14 MHz bandwidth, a noise figure ranging from 12.4 to 13.2 dB with a flicker corner frequency of 200 kHz and an input referred 1 dB compression point of -23.7 dBm. The circuit draws only 1.3 mA from a 1.0 V supply
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
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