16 research outputs found
AnalogâtoâDigital Conversion for Cognitive Radio: Subsampling, Interleaving, and Compressive Sensing
This chapter explores different analog-to-digital conversion techniques that are suitable to be implemented in cognitive radio receivers. This chapter details the fundamentals, advantages, and drawbacks of three promising techniques: subsampling, interleaving, and compressive sensing. Due to their major maturity, subsampling- and interleaving-based systems are described in further detail, whereas compressive sensing-based systems are described as a complement of the previous techniques for underutilized spectrum applications. The feasibility of these techniques as part of software-defined radio, multistandard, and spectrum sensing receivers is demonstrated by proposing different architectures with reduced complexity at circuit level, depending on the application requirements. Additionally, the chapter proposes different solutions to integrate the advantages of these techniques in a unique analog-to-digital conversion process
Design and analysis of multi-element antenna systems and agile radiofrequency frontends for automotive applications
Vehicular connectivity serves as one of the major enabling technologies for
current applications like driver assistance, safety and infotainment as well as
upcoming features like highly automated vehicles - all of which having certain
quality of service requirements, e. g. datarate or reliability. This work focuses on
vehicular integration of multiple-input-multiple-output (MIMO) capable multielement
antenna systems and frequency-agile radio frequency (RF) front ends
to cover current and upcoming connectivity needs. It is divided in four major
parts. For each part, mostly physical layer effects are analyzed (any performance
lost on physical layer, cannot be compensated in higher layers), sensitivities are
identified and novel concepts are introduced based on the status-quo findings.Fahrzeugvernetzung dient als eine der wesentlichsten BefÀhigungstechnologien
fĂŒr moderne Fahrerassistenzsysteme und zukĂŒnftig auch hochautomatisiertes
Fahren. Sowohl die heutigen als auch zukĂŒnftige Anwendungen haben besondere
DienstgĂŒteanforderungen, z.B. in Bezug auf die Datenrate oder VerlĂ€sslichkeit.
Im Rahmen dieser Arbeit wird die Integration von Mehrantennensystemen fĂŒr
MIMO-Funkanwendungen (MIMO: engl. Multiple Input Multiple Output) sowie
von frequenzagilen Hochfrequenzfrontends im Fahrzeugumfeld untersucht, um
so eine technische Grundlage fĂŒr zukĂŒnftige Anforderungen an die automobile
Vernetzung anbieten zu können. Die dabei gewonnenen Erkenntnisse lassen sich
in vier Teile gliedern. GrundsÀtzlich konzentrieren sich die Untersuchungen vorrangig
auf die physikalische Ebene. Auf Basis des aktuellen Status Quo werden
SensitivitÀten herausgearbeitet, neue Konzepte hergeleitet und entwickelt
Apport de l'échantillonnage aléatoire à temps quantifié pour le traitement en bande de base dans un contexte radio logicielle restreinte
The work presented in this Ph.D. dissertation deals with the design of multistandard radio receivers that process signals with heterogeneous specifications. The originality of these research activities comes from the application of random sampling at the baseband stage of a software defined radio receiver. The purpose behind the choice of random sampling is to take advantage of its alias-free feature. The originality of this work is the analytic proof of the alias attenuation feature of the time quantized random sampling, the implementation version of the random sampling. A second contribution concerns also the analytic study of the simplest implementation version of the random sampling, the time quantized pseudo-random sampling (TQ-PRS). Theoretical formulas allow the estimation of the alias attenuation in terms of time quantization factor and oversampling ratio. Alias attenuation measurement permits to design the baseband stage of the proposed multistandard radio receiver architecture. The design concerns different configuration of the baseband stage according to the performances of the used analog-to-digital converters (ADC). The TQPRS allows decreasing the anti-aliasing filter order or the sampling frequency. The design of the baseband stage reveals a difference on the choice of the time quantization factor for each standard. The power consumption budget analysis demonstrates a power consumption gain of 30% regarding the power consumption of the analog baseband stage. This gain becomes 27.5% when the TQ-PRS clock and the digital canal selection stages are considered.Ces travaux de recherche sâinscrivent dans le cadre de la conception de rĂ©cepteurs multistandard optimisĂ©s pouvant traiter des signaux Ă spĂ©cifications hĂ©tĂ©rogĂšnes. LâidĂ©e est dâappliquer lâĂ©chantillonnage alĂ©atoire au niveau de lâĂ©tage en bande de base dâun rĂ©cepteur radio logicielle restreinte afin de tirer profit de son pouvoir dâanti-repliement. La nouveautĂ© dans ces travaux est lâĂ©tude analytique de la rĂ©duction du repliement spectral par lâĂ©chantillonnage alĂ©atoire Ă temps quantifiĂ©, candidat favorable Ă lâimplĂ©mentation matĂ©rielle. Une deuxiĂšme contribution concerne aussi lâĂ©tude analytique de lâĂ©chantillonnage pseudo-alĂ©atoire Ă temps quantifiĂ© (TQ-PRS) dont lâimportance rĂ©side en sa grande facilitĂ© dâimplĂ©mentation matĂ©rielle. Les formulations thĂ©oriques ont permis dâestimer lâattĂ©nuation des rĂ©pliques en fonction du facteur de la quantification temporelle et du facteur du sur-Ă©chantillonnage. Les mesures de lâattĂ©nuation du repliement spectral ont permis de dimensionner lâĂ©tage en bande de base dâune architecture de rĂ©ception multistandard. Le dimensionnement sâintĂ©resse Ă diffĂ©rentes configurations de lâĂ©tage en bande de base rĂ©gies par les performances du convertisseur analogique numĂ©rique (ADC) utilisĂ©.Les travaux de recherche ont dĂ©montrĂ© que lâapplication du TQ-PRS au niveau de lâADC mĂšne soit Ă une rĂ©duction de lâordre du filtre anti-repliement soit Ă une rĂ©duction de la frĂ©quence dâĂ©chantillonnage. Un bilan global de la consommation de puissance a permis un gain de 30% de la consommation de lâĂ©tage en bande de base analogique. En tenant compte du gĂ©nĂ©rateur de lâhorloge TQ-PRS et de lâĂ©tage de sĂ©lection numĂ©rique du canal, ce gain devient 25%
Parametric analog signal amplification applied to nanoscale cmos wireless digital transceivers
Thesis presented in partial fulfillment of the requirements for the degree of Doctor
of Philosophy in the subject of Electrical and Computer Engineering by the Universidade Nova de Lisboa,Faculdade de CiĂȘncias e TecnologiaSignal amplification is required in almost every analog electronic system. However
noise is also present, thus imposing limits to the overall circuit performance, e.g., on
the sensitivity of the radio transceiver. This drawback has triggered a major research
on the field, which has been producing several solutions to achieve amplification with minimum added noise. During the Fifties, an interesting out of mainstream path was followed which was based on variable reactance instead of resistance based amplifiers.
The principle of these parametric circuits permits to achieve low noise amplifiers since
the controlled variations of pure reactance elements is intrinsically noiseless. The
amplification is based on a mixing effect which enables energy transfer from an AC
pump source to other related signal frequencies.
While the first implementations of these type of amplifiers were already available at that time, the discrete-time version only became visible more recently. This discrete-time version is a promising technique since it is well adapted to the mainstream nanoscale CMOS technology. The technique itself is based on the principle of changing the surface potential of the MOS device while maintaining the transistor gate in a floating state.
In order words, the voltage amplification is achieved by changing the capacitance value
while maintaining the total charge unchanged during an amplification phase.
Since a parametric amplifier is not intrinsically dependent on the transconductance of the MOS transistor, it does not directly suffer from the intrinsic transconductance MOS gain issues verified in nanoscale MOS technologies. As a consequence, open-loop and opamp free structures can further emerge with this additional contribution.
This thesis is dedicated to the analysis of parametric amplification with special emphasis on the MOS discrete-time implementation. The use of the latter is supported on the presentation of several circuits where the MOS Parametric Amplifier cell is well suited:
small gain amplifier, comparator, discrete-time mixer and filter, and ADC. Relatively to the latter, a high speed time-interleaved pipeline ADC prototype is implemented in a,standard 130 nm CMOS digital technology from United Microelectronics Corporation (UMC). The ADC is fully based on parametric MOS amplification which means that one could achieve a compact and MOS-only implementation. Furthermore, any high
speed opamp has not been used in the signal path, being all the amplification steps
implemented with open-loop parametric MOS amplifiers. To the authorâs knowledge,
this is first reported pipeline ADC that extensively used the parametric amplification
concept.Fundação para a CiĂȘncia e Tecnologia through
the projects SPEED, LEADER and IMPAC