8 research outputs found
Analysis and design of low-power data converters
In a large number of applications the signal processing is done exploiting both
analog and digital signal processing techniques. In the past digital and analog
circuits were made on separate chip in order to limit the interference and other
side effects, but the actual trend is to realize the whole elaboration chain on a
single System on Chip (SoC). This choice is driven by different reasons such as the
reduction of power consumption, less silicon area occupation on the chip and also
reliability and repeatability. Commonly a large area in a SoC is occupied by digital
circuits, then, usually a CMOS short-channel technological processes optimized to
realize digital circuits is chosen to maximize the performance of the Digital Signal
Proccessor (DSP). Opposite, the short-channel technology nodes do not represent
the best choice for analog circuits. But in a large number of applications, the signals
which are treated have analog nature (microphone, speaker, antenna, accelerometers,
biopotential, etc.), then the input and output interfaces of the processing chip are
analog/mixed-signal conversion circuits. Therefore in a single integrated circuit (IC)
both digital and analog circuits can be found. This gives advantages in term of total
size, cost and power consumption of the SoC. The specific characteristics of CMOS
short-channel processes such as:
• Low breakdown voltage (BV) gives a power supply limit (about 1.2 V).
• High threshold voltage VTH (compared with the available voltage supply) fixed
in order to limit the leakage power consumption in digital applications (of the
order of 0.35 / 0.4V), puts a limit on the voltage dynamic, and creates many
problems with the stacked topologies.
• Threshold voltage dependent on the channel length VTH = f(L) (short channel
effects).
• Low value of the output resistance of the MOS (r0) and gm limited by speed
saturation, both causes contribute to achieving a low intrinsic gain gmr0 = 20
to 26dB.
• Mismatch which brings offset effects on analog circuits.
make the design of high performance analog circuits very difficult. Realizing lowpower
circuits is fundamental in different contexts, and for different reasons: lowering
the power dissipation gives the capability to reduce the batteries size in mobile
devices (laptops, smartphones, cameras, measuring instruments, etc.), increase the
life of remote sensing devices, satellites, space probes, also allows the reduction of
the size and weight of the heat sink. The reduction of power dissipation allows the
realization of implantable biomedical devices that do not damage biological tissue.
For this reason, the analysis and design of low power and high precision analog
circuits is important in order to obtain high performance in technological processes
that are not optimized for such applications. Different ways can be taken to reduce
the effect of the problems related to the technology:
• Circuital level: a circuit-level intervention is possible to solve a specific problem
of the circuit (i.e. Techniques for bandwidth expansion, increase the gain,
power reduction, etc.).
• Digital calibration: it is the highest level to intervene, and generally going to
correct the non-ideal structure through a digital processing, these aims are
based on models of specific errors of the structure.
• Definition of new paradigms.
This work has focused the attention on a very useful mixed-signal circuit: the
pipeline ADC. The pipeline ADCs are widely used for their energy efficiency in
high-precision applications where a resolution of about 10-16 bits and sampling
rates above hundreds of Mega-samples per second (telecommunication, radar, etc.)
are needed. An introduction on the theory of pipeline ADC, its state of the art
and the principal non-idealities that affect the energy efficiency and the accuracy
of this kind of data converters are reported in Chapter 1. Special consideration is
put on low-voltage low-power ADCs. In particular, for ADCs implemented in deep
submicron technology nodes side effects called short channel effects exist opposed to
older technology nodes where undesired effects are not present. An overview of the
short channel effects and their consequences on design, and also power consuption
reduction techniques, with particular emphasis on the specific techniques adopted
in pipelined ADC are reported in Chapter 2. Moreover, another way may be
undertaken to increase the accuracy and the efficiency of an ADC, this way is the
digital calibration. In Chapter 3 an overview on digital calibration techniques, and
furthermore a new calibration technique based on Volterra kernels are reported. In
some specific applications, such as software defined radios or micropower sensor,
some circuits should be reconfigurable to be suitable for different radio standard
or process signals with different charateristics. One of this building blocks is the
ADC that should be able to reconfigure the resolution and conversion frequency. A
reconfigurable voltage-scalable ADC pipeline capable to adapt its voltage supply
starting from the required conversion frequency was developed, and the results are
reported in Chapter 4. In Chapter 5, a pipeline ADC based on a novel paradigm for
the feedback loop and its theory is described
Intelligent Sensor Networks
In the last decade, wireless or wired sensor networks have attracted much attention. However, most designs target general sensor network issues including protocol stack (routing, MAC, etc.) and security issues. This book focuses on the close integration of sensing, networking, and smart signal processing via machine learning. Based on their world-class research, the authors present the fundamentals of intelligent sensor networks. They cover sensing and sampling, distributed signal processing, and intelligent signal learning. In addition, they present cutting-edge research results from leading experts
Technology 2002: the Third National Technology Transfer Conference and Exposition, Volume 1
The proceedings from the conference are presented. The topics covered include the following: computer technology, advanced manufacturing, materials science, biotechnology, and electronics
GSI Scientific Report 2009 [GSI Report 2010-1]
Displacement design response spectrum is an essential component for the currently-developing displacement-based seismic design and assessment procedures. This paper proposes a new and simple method for constructing displacement design response spectra on soft soil sites. The method takes into account modifications of the seismic waves by the soil layers, giving due considerations to factors such as the level of bedrock shaking, material non-linearity, seismic impedance contrast at the interface between soil and bedrock, and plasticity of the soil layers. The model is particularly suited to applications in regions with a paucity of recorded strong ground motion data, from which empirical models cannot be reliably developed