55 research outputs found
Noise analysis of modulated quantizer based on oversampled signals
In this paper, a noise analysis of a modulated quantizer is performed. If input signals are oversampled, then the quantization error could be reduced by modulating both the input and the output of the quantizer. The working principle is based on the fact that convolutions of bandpass signals would spread wider in the frequency spectrum than that of lowpass signals. Hence, by filtering the high frequency components, the signal-to-noise ratio (SNR) could be increased. Numerical simulation results show that the modulated quantization scheme could achieve an average of 13.0960dB to 21.4700dB improvements on SNR over the conventional scheme, depends on the types of bandlimited input signals
Multi-bit sigma-delta modulators with enhanced dynamic-range using non-linear DAC for hearing aids
15th IEEE International Conference on Electronics, Circuits and Systems, MaltaThis paper presents the possibility of employing nonlinear low-resolution DACs in the feedback paths of multi-bit second-order Sigma-Delta modulators. The proposed technique is particularly attractive in applications such as hearing aids, requiring a very large dynamic range and medium signal-tonoise-plus-distortion-ratio. As demonstrated through simulated results in which noise and mismatch effects are included, for the same over-sampling ratio, improvements in the order of 6-to-9 dB in the dynamic range can be achieved when comparing with the same topology employing linear-DACs
Noise Weighting in the Design of {\Delta}{\Sigma} Modulators (with a Psychoacoustic Coder as an Example)
A design flow for {\Delta}{\Sigma} modulators is illustrated, allowing
quantization noise to be shaped according to an arbitrary weighting profile.
Being based on FIR NTFs, possibly with high order, the flow is best suited for
digital architectures. The work builds on a recent proposal where the modulator
is matched to the reconstruction filter, showing that this type of optimization
can benefit a wide range of applications where noise (including in-band noise)
is known to have a different impact at different frequencies. The design of a
multiband modulator, a modulator avoiding DC noise, and an audio modulator
capable of distributing quantization artifacts according to a psychoacoustic
model are discussed as examples. A software toolbox is provided as a general
design aid and to replicate the proposed results.Comment: 5 pages, 18 figures, journal. Code accompanying the paper is
available at http://pydsm.googlecode.co
量子化誤差削減のためのΔΣ変調器のノイズ整形フィルタの設計
広島大学(Hiroshima University)博士(工学)Doctor of Engineeringdoctora
Quantization and Compressive Sensing
Quantization is an essential step in digitizing signals, and, therefore, an
indispensable component of any modern acquisition system. This book chapter
explores the interaction of quantization and compressive sensing and examines
practical quantization strategies for compressive acquisition systems.
Specifically, we first provide a brief overview of quantization and examine
fundamental performance bounds applicable to any quantization approach. Next,
we consider several forms of scalar quantizers, namely uniform, non-uniform,
and 1-bit. We provide performance bounds and fundamental analysis, as well as
practical quantizer designs and reconstruction algorithms that account for
quantization. Furthermore, we provide an overview of Sigma-Delta
() quantization in the compressed sensing context, and also
discuss implementation issues, recovery algorithms and performance bounds. As
we demonstrate, proper accounting for quantization and careful quantizer design
has significant impact in the performance of a compressive acquisition system.Comment: 35 pages, 20 figures, to appear in Springer book "Compressed Sensing
and Its Applications", 201
Analysis of Nonlinear Behaviors, Design and Control of Sigma Delta Modulators
M PhilSigma delta modulators (SDMs) have been widely applied in analogue-to-digital
(A/D) conversion for many years. SDMs are becoming more and more popular in power
electronic circuits because it can be viewed and applied as oversampled A/D converters
with low resolution quantizers. The basic structure of an SDM under analytical
investigation consists of a loop filter and a low bit quantizer connected by a negative
feedback loop.
Although there are numerous advantages of SDMs over other A/D converters, the
application of SDMs is limited by the unboundedness of the system states and their
nonlinear behaviors. It was found that complex dynamical behaviors exist in low bit
SDMs, and for a bandpass SDM, the state space dynamics can be represented by elliptic
fractal patterns confined within two trapezoidal regions. In all, there are three types of
nonlinear behaviors, namely fixed point, limit cycle and chaotic behaviors. Related to the
unboundedness issue, divergent behavior of system states is also a commonly discovered
phenomenon. Consequently, how to design and control the SDM so that the system states
are bounded and the unwanted nonlinear behaviors are avoided is a hot research topic
worthy of investigated.
In our investigation, we perform analysis on such complex behaviors and
determine a control strategy to maintain the boundedness of the system states and avoid
the occurrence of limit cycle behavior. For the design problem, we impose constraints
based on the performance of an SDM and determine an optimal design for the SDM. The
results are significantly better than the existing approaches
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