Spectrum shaping and its application: spread-spectrum clock generator and circuits for ultra wide band

Electromagnetic spectrum can be identified as a resource for the designer, as well as for the manufacturer, from two complementary points of view: first, because it is a good in great demand by many different kind of applications; second, because despite its scarce availability, it may be advantageous to use more spectrum than necessary. This is the case of Spread-Spectrum Systems, those systems in which the transmitted signal is spread over a wide frequency band, much wider, in fact, than the minimum bandwidth required to transmit the information being sent. Part I of this dissertation deals with Spread-Spectrum Clock Generators (SSCG) aiming at reducing Electro Magnetic Interference (EMI) of clock signals in integrated circuits (IC) design. In particular, the modulation of the clock and the consequent spreading of its spectrum are obtained through a random modulating signal outputted by a chaotic map, i.e. a discrete-time dynamical system showing chaotic behavior. The advantages offered by this kind of modulation are highlighted. Three different prototypes of chaos-based SSCG are presented in all their aspects: design, simulation, and post-fabrication measurements. The third one, operating at a frequency equal to 3GHz, aims at being applied to Serial ATA, standard de facto for fast data transmission to and from Hard Disk Drives. The most extreme example of spread-spectrum signalling is the emerging ultra-wideband (UWB) technology, which proposes the use of large sections of the radio spectrum at low amplitudes to transmit high-bandwidth digital data. In part II of the dissertation, two UWB applications are presented, both dealing with the advantages as well as with the challenges of a wide-band system, namely: a chaos-based sequence generation method for reducing Multiple Access Interference (MAI) in Direct Sequence UWB Wireless-Sensor-Networks (WSNs), and design and simulations of a Low-Noise Amplifier (LNA) for impulse radio UWB. This latter topic was studied during a study-abroad period in collaboration with Delft University of Technology, Delft, Netherlands.

Hardware and software development of a multichannel readout board named CARLOSrx for the ALICE experiment

ALICE, that is an experiment held at CERN using the LHC, is specialized in analyzing lead-ion collisions. ALICE will study the properties of quarkgluon plasma, a state of matter where quarks and gluons, under conditions of very high temperatures and densities, are no longer confined inside hadrons. Such a state of matter probably existed just after the Big Bang, before particles such as protons and neutrons were formed. The SDD detector, one of the ALICE subdetectors, is part of the ITS that is composed by 6 cylindrical layers with the innermost one attached to the beam pipe. The ITS tracks and identifies particles near the interaction point, it also aligns the tracks of the articles detected by more external detectors. The two ITS middle layers contain the whole 260 SDD detectors. A multichannel readout board, called CARLOSrx, receives at the same time the data coming from 12 SDD detectors. In total there are 24 CARLOSrx boards needed to read data coming from all the SDD modules (detector plus front end electronics). CARLOSrx packs data coming from the front end electronics through optical link connections, it stores them in a large data FIFO and then it sends them to the DAQ system. Each CARLOSrx is composed by two boards. One is called CARLOSrx data, that reads data coming from the SDD detectors and configures the FEE; the other one is called CARLOSrx clock, that sends the clock signal to all the FEE. This thesis contains a description of the hardware design and firmware features of both CARLOSrx data and CARLOSrx clock boards, which deal with all the SDD readout chain. A description of the software tools necessary to test and configure the front end electronics will be presented at the end of the thesis.

Architetture di interconnessione per sistemi su singolo chip e per sistemi ad integrazione tridimensionale

I continui sviluppi nel campo della fabbricazione dei circuiti integrati hanno comportato frequenti travolgimenti nel design, nell’implementazione e nella scalabilità dei device elettronici, così come nel modo di utilizzarli. Anche se la legge di Moore ha anticipato e caratterizzato questo trend nelle ultime decadi, essa stessa si trova a fronteggiare attualmente enormi limitazioni, superabili solo attraverso un diverso approccio nella produzione di chip, consistente in pratica nella sovrapposizione verticale di diversi strati collegati elettricamente attraverso speciali vias. Sul singolo strato, le network on chip sono state suggerite per ovviare le profonde limitazioni dovute allo scaling di strutture di comunicazione condivise. Questa tesi si colloca principalmente nel contesto delle nascenti piattaforme multicore ad alte prestazioni basate sulle 3D NoC, in cui la network on chip viene estesa nelle 3 direzioni. L’obiettivo di questo lavoro è quello di fornire una serie di strumenti e tecniche per poter costruire e aratterizzare una piattaforma tridimensionale, cosi come dimostrato nella realizzazione del testchip 3D NOC fabbricato presso la fonderia IMEC. Il primo contributo è costituito sia una accurata caratterizzazione delle interconnessioni verticali (TSVs) (ovvero delle speciali vias che attraversano l’intero substrato del die), sia dalla caratterizzazione dei router 3D (in cui una o più porte sono estese nella direzione verticale) ed infine dal setup di un design flow 3D utilizzando interamente CAD 2D. Questo primo step ci ha permesso di effettuare delle analisi dettagliate sia sul costo sia sulle varie implicazioni. Il secondo contributo è costituito dallo sviluppo di alcuni blocchi funzionali necessari per garantire il corretto funziomento della 3D NoC, in presenza sia di guasti nelle TSVs (fault tolerant links) che di deriva termica nei vari clock tree dei vari die (alberi di clock indipendenti). Questo secondo contributo è costituito dallo sviluppo delle seguenti soluzioni circuitali: 3D fault tolerant link, Look Up Table riconfigurabili e un sicnronizzatore mesocrono. Il primo è costituito fondamentalmente un bus verticale equipaggiato con delle TSV di riserva da utilizzare per rimpiazzare le vias guaste, più la logica di controllo per effettuare il test e la riconfigurazione. Il secondo è rappresentato da una Look Up Table riconfigurabile, ad alte prestazioni e dal costo contenuto, necesaria per bilanciare sia il traffico nella NoC che per bypassare link non riparabili. Infine la terza soluzione circuitale è rappresentata da un sincronizzatore mesocrono necessario per garantire la sincronizzazione nel trasferimento dati da un layer and un altro nelle 3D Noc. Il terzo contributo di questa tesi è dato dalla realizzazione di un interfaccia multicore per memorie 3D (stacked 3D DRAM) ad alte prestazioni, e dall’esplorazione architetturale dei benefici e del costo di questo nuovo sistema in cui il la memoria principale non è piu il collo di bottiglia dell’intero sistema. Il quarto ed ultimo contributo è rappresentato dalla realizzazione di un 3D NoC test chip presso la fonderia IMEC, e di un circuito full custom per la caratterizzazione della variability dei parametri RC delle interconnessioni verticali.

Cooperative Wireless Systems

This Ph.D. dissertation reports on the work performed at the Wireless Communication Laboratory - University of Bologna and National Research Council - as well as, for six months, at the Fraunhofer Institute for Integrated Circuit (IIS) in Nürnberg. The work of this thesis is in the area of wireless communications, especially with regards to cooperative communications aspects in narrow-band and ultra-wideband systems, cooperative links characterization, network geometry, power allocation techniques,and synchronization between nodes. The underpinning of this work is devoted to developing a general framework for design and analysis of wireless cooperative communication systems, which depends on propagation environment, transmission technique, diversity method, power allocation for various scenarios and relay positions. The optimal power allocation for minimizing the bit error probability at the destination is derived. In addition, a syncronization algorithm for master-slave communications is proposed with the aim of jointly compensate the clock drift and offset of wireless nodes composing the network.

Context-aware wireless networks

This thesis investigates context-aware wireless networks, capable to adapt their behavior to the context and the application, thanks to the ability of combining communication, sensing and localization. Problems of signals demodulation, parameters estimation and localization are addressed exploiting analytical methods, simulations and experimentation, for the derivation of the fundamental limits, the performance characterization of the proposed schemes and the experimental validation. Ultrawide-bandwidth (UWB) signals are in certain cases considered and non-coherent receivers, allowing the exploitation of the multipath channel diversity without adopting complex architectures, investigated. Closed-form expressions for the achievable bit error probability of novel proposed architectures are derived. The problem of time delay estimation (TDE), enabling network localization thanks to ranging measurement, is addressed from a theoretical point of view. New fundamental bounds on TDE are derived in the case the received signal is partially known or unknown at receiver side, as often occurs due to propagation or due to the adoption of low-complexity estimators. Practical estimators, such as energy-based estimators, are revised and their performance compared with the new bounds. The localization issue is addressed with experimentation for the characterization of cooperative networks. Practical algorithms able to improve the accuracy in non-line-of-sight (NLOS) channel conditions are evaluated on measured data. With the purpose of enhancing the localization coverage in NLOS conditions, non-regenerative relaying techniques for localization are introduced and ad hoc position estimators are devised. An example of context-aware network is given with the study of the UWB-RFID system for detecting and locating semi-passive tags. In particular a deep investigation involving low-complexity receivers capable to deal with problems of multi-tag interference, synchronization mismatches and clock drift is presented. Finally, theoretical bounds on the localization accuracy of this and others passive localization networks (e.g., radar) are derived, also accounting for different configurations such as in monostatic and multistatic networks.

Modelling and Design of Advanced Reliable Circuits and Devices for Energy Efficiency

Reliable electronic systems, namely a set of reliable electronic devices connected to each other and working correctly together for the same functionality, represent an essential ingredient for the large-scale commercial implementation of any technological advancement. Microelectronics technologies and new powerful integrated circuits provide noticeable improvements in performance and cost-effectiveness, and allow introducing electronic systems in increasingly diversified contexts. On the other hand, opening of new fields of application leads to new, unexplored reliability issues. The development of semiconductor device and electrical models (such as the well known SPICE models) able to describe the electrical behavior of devices and circuits, is a useful means to simulate and analyze the functionality of new electronic architectures and new technologies. Moreover, it represents an effective way to point out the reliability issues due to the employment of advanced electronic systems in new application contexts. In this thesis modeling and design of both advanced reliable circuits for general-purpose applications and devices for energy efficiency are considered. More in details, the following activities have been carried out: first, reliability issues in terms of security of standard communication protocols in wireless sensor networks are discussed. A new communication protocol is introduced, allows increasing the network security. Second, a novel scheme for the on-die measurement of either clock jitter or process parameter variations is proposed. The developed scheme can be used for an evaluation of both jitter and process parameter variations at low costs. Then, reliability issues in the field of “energy scavenging systems” have been analyzed. An accurate analysis and modeling of the effects of faults affecting circuit for energy harvesting from mechanical vibrations is performed. Finally, the problem of modeling the electrical and thermal behavior of photovoltaic (PV) cells under hot-spot condition is addressed with the development of an electrical and thermal model.

Epigenetics of nutrition in aging

There is a need to identify factors that are able to influence health in old age and to develop interventions that could slow down the process of aging and its associated pathologies. Lifestyle modifications, and especially nutrition, appear to be promising strategies to promote healthy aging. Their impact on aging biomarkers has been poorly investigated. In the first part of this work, we evaluated the impact of a one-year Mediterranean-like diet, delivered within the framework of the NU-AGE project in 120 elderly subjects, on epigenetic age acceleration measures assessed with Horvath’s clock. We observed a rejuvenation of participants after nutritional intervention. The effect was more marked in the group of Polish females and in subjects who were epigenetically older at baseline. In the second part of this work, we developed a new model of epigenetic biomarker, based on a gene-targeted approach with the EpiTYPER® system. We selected six regions of interest (associated with ELOVL2, NHLRC1, SIRT7/MAFG, AIM2, EDARADD and TFAP2E genes) and constructed our model through a ridge regression analysis. In controls, estimation of chronological age was accurate, with a correlation coefficient between predicted and chronological age of 0.92 and a mean absolute deviation of 4.70 years. Our model was able to capture phenomena of accelerated or decelerated aging, in Down syndrome subjects and centenarians and offspring respectively. Applying our model to samples of the NU-AGE project, we observed similar results to the ones obtained with the canonical epigenetic clock, with a rejuvenation of the individuals after one-year of nutritional intervention. Together, our findings indicate that nutrition can promote epigenetic rejuvenation and that epigenetic age acceleration measures could be suitable biomarkers to evaluate their impact. We demonstrated that the effect of the dietary intervention is country-, sex- and individual-specific, thus suggesting the need for a personalized approach to nutritional interventions.

Marcatori di eta biologica nella malattia di Parkinson: risultati di un'analisi glicomica e epigenomica

La malattia di Parkinson è una malattia neurodegenerativa caratterizzata da una progressiva disfunzione motoria e cognitiva. È noto che l'età avanzata è il principale fattore di rischio per la malattia di Parkinson e alcuni studi hanno dimostrato un'accelerazione dell'età biologica nelle fasi più avanzate della malattia. Questo studio si propone di valutare se l'accelerazione dell'invecchiamento biologico descritta nelle fasi avanzate della malattia di Parkinson caratterizzi anche le prime fasi della malattia. A tal fine sono stati utilizzati due tipi di marcatori biologici di età, basati sull'analisi della metilazione del DNA del sangue (l'orologio epigenetico e sue varianti) e dei profili degli N-glicani nel plasma (GlycoAge Test). I biomarcatori sono stati valutati in campioni ottenuti da pazienti con malattia di Parkinson de novo, con diagnosi recente e non ancora in trattamento farmacologico, nonché da pazienti con stadi più avanzati della malattia e da controlli sani. I risultati ottenuti nelle prime fasi della malattia non mostrano segni di invecchiamento accelerato, che trovano conferma nelle fasi più avanzate. Dai dati di metilazione è possibile prevedere le proporzioni delle diverse popolazioni di leucociti. Questa analisi nelle prime fasi della malattia ha già evidenziato significative alterazioni che seguono in parte quelle caratteristiche dell'invecchiamento del sistema immunitario, suggerendo un'immunosenescenza accelerata nella malattia di Parkinson. Infine, i dati sulla metilazione del DNA sono stati analizzati per identificare le differenze nelle regioni metilate del genoma tra pazienti con malattia di Parkinson e controlli. I risultati suggeriscono l'esistenza di piccole ma significative alterazioni nella metilazione del DNA che caratterizzano lo stadio precoce e/o avanzato della malattia. In conclusione, questo studio suggerisce che le prime fasi della malattia di Parkinson sono caratterizzate da specifiche alterazioni epigenetiche e invecchiamento precoce del sistema immunitario, che tuttavia non si traducono in un'alterazione dei biomarcatori di invecchiamento epigenetici e glicomici.