CMOS design of chaotic oscillators using state variables: a monolithic Chua's circuit

This paper presents design considerations for monolithic implementation of piecewise-linear (PWL) dynamic systems in CMOS technology. Starting from a review of available CMOS circuit primitives and their respective merits and drawbacks, the paper proposes a synthesis approach for PWL dynamic systems, based on state-variable methods, and identifies the associated analog operators. The GmC approach, combining quasi-linear VCCS's, PWL VCCS's, and capacitors is then explored regarding the implementation of these operators. CMOS basic building blocks for the realization of the quasi-linear VCCS's and PWL VCCS's are presented and applied to design a Chua's circuit IC. The influence of GmC parasitics on the performance of dynamic PWL systems is illustrated through this example. Measured chaotic attractors from a Chua's circuit prototype are given. The prototype has been fabricated in a 2.4- mu m double-poly n-well CMOS technology, and occupies 0.35 mm/sup 2/, with a power consumption of 1.6 mW for a +or-2.5-V symmetric supply. Measurements show bifurcation toward a double-scroll Chua's attractor by changing a bias current

Constraint satisfaction modules : a methodology for analog circuit design

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.Includes bibliographical references (p. 119-122).This dissertation describes a methodology for solving convex constraint problems using analog circuits. It demonstrates how this methodology can be used to design circuits that solve function-fitting problems through iterated gradient descent. In particular, it shows how to build a small circuit that can model a nonlinearity by observation, and predistort to compensate for this nonlinearity. The system fits into a broader effort to investigate non-traditional approaches to circuit design. First, it breaks the traditional input-output abstraction barrier; all ports are bidirectional. Second, it uses a different methodology for proving system stability with local rather than global properties. Such stability arguments can be scaled to much more complex systems than traditional stability criteria.by Piotr Mitros.Ph.D

Joint signal detection and channel estimation in rank-deficient MIMO systems

L'évolution de la prospère famille des standards 802.11 a encouragé le développement des technologies appliquées aux réseaux locaux sans fil (WLANs). Pour faire face à la toujours croissante nécessité de rendre possible les communications à très haut débit, les systèmes à antennes multiples (MIMO) sont une solution viable. Ils ont l'avantage d'accroître le débit de transmission sans avoir recours à plus de puissance ou de largeur de bande. Cependant, l'industrie hésite encore à augmenter le nombre d'antennes des portables et des accésoires sans fil. De plus, à l'intérieur des bâtiments, la déficience de rang de la matrice de canal peut se produire dû à la nature de la dispersion des parcours de propagation, ce phénomène est aussi occasionné à l'extérieur par de longues distances de transmission. Ce projet est motivé par les raisons décrites antérieurement, il se veut un étude sur la viabilité des transcepteurs sans fil à large bande capables de régulariser la déficience de rang du canal sans fil. On vise le développement des techniques capables de séparer M signaux co-canal, même avec une seule antenne et à faire une estimation précise du canal. Les solutions décrites dans ce document cherchent à surmonter les difficultés posées par le medium aux transcepteurs sans fil à large bande. Le résultat de cette étude est un algorithme transcepteur approprié aux systèmes MIMO à rang déficient

Arrayable Voltage-Controlled Ring-Oscillator for Direct Time-of-Flight Image Sensors

Direct time-of-flight (d-ToF) estimation with high frame rate requires the incorporation of a time-to-digital converter (TDC) at pixel level. A feasible approach to a compact implementation of the TDC is to use the multiple phases of a voltage-controlled ring-oscillator (VCRO) for the finest bits. The VCRO becomes central in determining the performance parameters of a d-ToF image sensor. In this paper, we are covering the modeling, design, and measurement of a CMOS pseudo-differential VCRO. The oscillation frequency, the jitter due to mismatches and noise and the power consumption are analytically evaluated. This design has been incorporated into a 64x64-pixel array. It has been fabricated in a 0.18 mu m standard CMOS technology. Occupation area is 28x29 mu m(2) and power consumption is 1.17 mW at 850 MHz. The measured gain of the VCRO is of 477 MHz/V with a frequency tuning range of 53%. Moreover, it features a linearity of 99.4% over a wide range of control frequencies, namely, from 400 to 850 MHz. The phase noise is of -102 dBc/Hz at 2 MHz offset frequency from 850 MHz. The influence of these parameters in the performance of the TDC has been measured. The minimum time bin of the TDC is 147 ps with a rms DNL/INL of 0.13/1.7LSB.Office of Naval Research (USA) N000141410355Ministerio de Economía y Competitividad TEC2015-66878-C3-1-RJunta de Andalucía P12-TIC 233

The missing applications found: Robust design techniques and novel uses of memristors

Resistive memory, also known as memristor, is an emerging potential successor to traditional CMOS charge based memories. Memristors have also recently been proposed as a promising candidate for several additional applications such as logic design, sensing, non-volatile storage, neuromorphic computing, Physically Unclonable Functions (PUFs), Content­addressable memory (CAM) and reconfigurable computing. In this paper, we explore three unique applications of memris­tor technology based implementations, specifically from the perspective of sensing, logic, in-memory computing and their solutions. We review solar cell health monitoring and diagnosis, describe the proposed solutions, and provide directions in memristive gas sensing and in-memory computing. For the gas sensor application, in order to determine the number of memristors to ensure a certain level of accuracy in sen­sitivity, a technique to optimize the sensor array based on an acceptable sensitivity variation and minimum sensitivity margin is presented. These "out-of-the-box" emerging ideas for applications of memristive devices in enhancing robustness and, at the same time, how the requirements of robust design are enabling unconventional use of the devices. To this end, the papers considers some examples of this mutual interaction

Low-Cost Test and Characterization Platform for Memristors

The electrical Testing and Characterization of the devices built under research conditions on silicon wafers, diced wafers, or package parts have hampered research since the beginning of integrated circuits. The challenges of performing electrical characterization on devices are to acquire useful and accurate data, the ease of use of the test platform, the portability of the test equipment, the ability to automate quickly, to allow modifications to the platform, the ability to change the configuration of the Device Under Test (DUT) or the Memristor Based Design (MBD), and to do this within budget. The devices that this research is focused on are memristors with unique test challenges. Some of the tests performed on memristors are Voltage sweeps, pulsing of Voltages, and threshold Voltages. Standard methods of testing memristors usually require hands-on experience, multiple bulky work stations, and hours of training. This work reports a novel, low-cost, portable test and characterization platform for many types of memristors with a voltage range from -10V to +10V, which is portable, low-cost, built with off-the-shelf components, and with configurability through software and hardware. To demonstrate the performance of the platform, the platform was able to take a virgin memristor from “forming” to operation voltages, and then incrementally change resistances by Voltage Pulsing. The platform within this work allows the researcher flexibility in electrical characterization by being able to accept many memristor types and MBDs, and applying environmental conditions to the MBD, with this flexibility of the platform the productivity of the researcher will increase

Accounting for total quality management

This thesis examines changes to the culture of three manufacturing organisations, two of which had implemented total quality management (TQM), and one in which a TQM implementation was unsuccessful. The effects of this organisational change on accounting systems and accountants were also examined. Ethnographic research was carried out in the three organisations, using several methods of evidence gathering: semi-formal and informal interviews and conversations, analysis of documents (such as internal accounting reports, newsletters, non-financial performance measures, production records, and newspaper, magazine and journal articles), and non-participant observation at meetings and in the factories. The evidence was viewed from three different perspectives, as promoted by Martin & Meyerson (1988), looking at integration, differentiation and ambiguity. Content themes characteristic of TQM and documented changes to management accounting systems subsequent to TQM implementation were identified in the literature. The practices and artifacts in each organisation were then compared with each other and with the content themes. The integration perspective highlights consensus between content themes, practices and artifacts, and between organisational actors. It assumes a unitary culture with a powerful change agent effecting the organisational change. Seen from this perspective, two of the organisations had made cultural changes consistent with TQM characteristics, and had also made many of the changes to accounting systems predicted in the literature. However, looking at the evidence from the differentiation perspective uncovered many examples of lack of consensus and conflict both between content themes themselves and between content themes, practices and artifacts. One of the “successful” organisations had made few changes to its accounting systems and had several subcultures which resisted change. The simultaneous existence of both harmony and conflict, and consensus and lack of it results in ambiguity for the organisational members. People differ in the way in which they deal with ambiguity, ranging from action paralysis through to using it as a motivation for innovation. The presence of ambiguity provides an explanation for the lack of success in implementing TQM in the third organisation, and for the lack of accounting change in one of the organisations which had successfully changed to TQM. This research contributes to knowledge in two ways. Firstly, it uses all three of Martin & Meyerson’s (1988) paradigms to look at TQM environments. This model has not been used in this setting before. Secondly, in using ambiguity to explain cultural and accounting change (or the lack of it), it provides an alternative viewpoint to the literature to date, which has been exclusively integrative and differentiating