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21
A CMOS Area Image Sensor With Pixel Level A/D Conversion
 IN ISSCC DIGEST OF TECHNICAL PAPERS
, 1995
"... A CMOS 64 x 64 pixel area image sensor chip using SigmaDelta modulation at each pixel for A/D conversion is described. The image data output is digital. The chip was fabricated using a 1.2µm two layer metal single layer poly nwell CMOS process. Each pixel block consists of a phototransistor and ..."
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Cited by 26 (7 self)
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A CMOS 64 x 64 pixel area image sensor chip using SigmaDelta modulation at each pixel for A/D conversion is described. The image data output is digital. The chip was fabricated using a 1.2µm two layer metal single layer poly nwell CMOS process. Each pixel block consists of a phototransistor and 22 MOS transistors. Test results demonstrate a dynamic range potentially greater than 93dB, a signal to noise ratio (SNR) of up to 61dB, and dissipation of less than 1mW with a 5V power supply.
Design of a lowlightlevel image sensor with an onchip sigmadelta analogtodigital conversion
 in CCDs and Outical Sensors 111, Proc. SPIE
"... The design of a lowlightlevel CMOS activepixelsensor (APS) with onchip, semiparallel analogtodigital (A/D) conversion is presented. The imager consists of a 128x128 array of active pixels at a 50 im pitch. Each column of pixels shares a 10bit A/D converter based on firstorder oversampled s ..."
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Cited by 18 (13 self)
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The design of a lowlightlevel CMOS activepixelsensor (APS) with onchip, semiparallel analogtodigital (A/D) conversion is presented. The imager consists of a 128x128 array of active pixels at a 50 im pitch. Each column of pixels shares a 10bit A/D converter based on firstorder oversampled sigmadelta (>z) modulation. The 10bit outputs of each converter are multiplexed and read out through a single set of outputs. A semiparallel architecture is chosen to achieve 30 frames/second operation even at low light levels. The sensor is designed for less than 10 e rms noise performance. A 28x28 activepixelsensor (APS) with 40x40p.tm2 pixels as well as individual elements of the sigmadelta modulator have been fabricated and tested using MOSIS * 2 m CMOS technology. 1.
Noise reduction in oversampled filter banks using predictive quantization
 IEEE Transactions on Information Theory
, 2001
"... Abstract—We introduce two methods for quantization noise reduction in oversampled filter banks. These methods are based on predictive quantization (noise shaping or linear prediction). It is demonstrated that oversampled noise shaping or linear predictive subband coders are well suited for subband c ..."
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Cited by 18 (1 self)
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Abstract—We introduce two methods for quantization noise reduction in oversampled filter banks. These methods are based on predictive quantization (noise shaping or linear prediction). It is demonstrated that oversampled noise shaping or linear predictive subband coders are well suited for subband coding applications where, for technological or other reasons, lowresolution quantizers have to be used. In this case, oversampling combined with noise shaping or linear prediction improves the effective resolution of the subband coder at the expense of increased rate. Simulation results are provided to assess the achievable quantization noise reduction and resolution enhancement, and to investigate the ratedistortion properties of the proposed methods. Index Terms—Filter banks, frame theory, linear prediction, noise reduction, noise shaping, oversampling, quantization, ratedistortion theory, sigma–delta converter, subband coding.
Rate Distortion Performance in Coding BandLimited Sources by Sampling and Dithered Quantization
 IEEE Trans. Inform. Theory
, 1995
"... The ratedistortion characteristics of a scheme for encoding continuoustime bandlimited stationary sources, with a prescribed band, is considered. In this coding procedure the input is sampled at Nyquist's rate or faster, the samples undergo dithered uniform or lattice quantization, using subtract ..."
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Cited by 17 (5 self)
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The ratedistortion characteristics of a scheme for encoding continuoustime bandlimited stationary sources, with a prescribed band, is considered. In this coding procedure the input is sampled at Nyquist's rate or faster, the samples undergo dithered uniform or lattice quantization, using subtractive dither, and the quantizer output is entropy coded. The ratedistortion performance, and the tradeoff between the sampling rate and the quantization accuracy is investigated, utilizing the observation that the coding scheme is equivalent to an additive noise channel. It is shown that the meansquare error of the scheme is fixed as long as the product of the sampling period and the quantizer second moment is kept constant, while for a fixed distortion the coding rate generally increases when the sampling rate exceeds the Nyquist rate. Finally, as the lattice quantizer dimension becomes large, the equivalent additive noise channel of the scheme tends to be Gaussian, and both the rate and t...
New properties of sigmadelta modulators with dc inputs
 Communications, IEEE Transactions on
, 1992
"... AbstractWe derive new properties of the single and doubleloop sigmadelta modulators with constant inputs, by exploiting the inherent structure of the output sequences or codewords that the modulators are capable of producing. Specifically, we first derive upper bounds of O(.Y2) and O(Y3) on the ..."
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Cited by 8 (2 self)
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AbstractWe derive new properties of the single and doubleloop sigmadelta modulators with constant inputs, by exploiting the inherent structure of the output sequences or codewords that the modulators are capable of producing. Specifically, we first derive upper bounds of O(.Y2) and O(Y3) on the number of rbit codewords for the single and doubleloop modulators, respectively. We then derive analytical lower bounds on the mean squared error (MSE) obtainable by any decoder, linear or nonlinear, in approximating the constant input; based on.Ybit codewords, the bounds are O(.Y3) and O(AT6) for the single and doubleloop modulators, respectively. Optimal nonlinear decoders for constant inputs can be based on a table lookup approach which operates directly on the nonuniform quantization intervals. Numerical results show that if the constant input is uniformly distributed, the MSE of such nonlinear decoders are 0(?*3) and O(S’) for the single and doubleloop modulators, respectively. Using simulations we find that the optimal nonlinear decoders perform better than linear decoders, by about 3 and 20 dB for the single and doubleloop modulators, respectively. We also introduce a cascade structure specifically for constant inputs, and derive its corresponding decoding algorithm. The idea behind the cascade structure is to requantize the residue from each stage in order to fully utilize the dynamic range of the next stage. We show that for a fixed latency, the MSE performance of our cascade structure is 12 dB superior, and its throughput is twice the conventional twostage MASH modulator. I.
Wilsontype oversampled cosine modulated filter banks with linear phase
 in Proc. 30th Asilomar Conf. Signals, Syst., Computers
, 1996
"... Abstract—Oversampled filter banks (FB’s) offer more design freedom and better noise immunity than critically sampled FB’s. Due to the increased computational complexity caused by oversampling, oversampled FB’s allowing an efficient implementation, such as cosine modulated filter banks (CMFB’s), are ..."
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Cited by 7 (1 self)
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Abstract—Oversampled filter banks (FB’s) offer more design freedom and better noise immunity than critically sampled FB’s. Due to the increased computational complexity caused by oversampling, oversampled FB’s allowing an efficient implementation, such as cosine modulated filter banks (CMFB’s), are of particular interest. So far, only critically sampled CMFB’s have been considered. In this paper, we introduce oversampled CMFB’s with perfect reconstruction (PR). Extending a classification of CMFB’s recently proposed by Gopinath, we consider two types of oversampled CMFB’s with PR. One of these types allows linear phase filters in all channels, and comprises CMFB’s recently introduced by Lin and Vaidyanathan as well as Wilsontype CMFB’s. For both types of oversampled CMFB’s, we formulate PR conditions in the time, frequency, and polyphase domains. It is shown that any PR CMFB corresponds to a PR DFT FB with twice the oversampling factor and that (under a specific condition) the same PR prototype can be used for both CMFB types. We also show that the frametheoretic properties of a CMFB and of the corresponding DFT FB are closely related. In particular, it is demonstrated that the minimumnorm synthesis prototype in an oversampled PR CMFB equals that in the corresponding DFT FB. Finally, we briefly address design methods and the efficient DCT/DSTbased implementation of oversampled CMFB’s. Index Terms—Cosine modulated filter banks, DFT filter banks, frame theory, oversampled filter banks. I.
Deterministic Analysis of Oversampled A/D Conversion and Sigma/Delta Modulation, and Decoding Improvements using Consistent Estimates
, 1993
"... Analogtodigital conversion (ADC) which consists in a double discretization of an analog signal in time and in amplitude is increasingly used in modern data acquisition. However, the conversion process always implies some loss of information due to amplitude quantization. Oversampling is the techni ..."
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Cited by 6 (0 self)
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Analogtodigital conversion (ADC) which consists in a double discretization of an analog signal in time and in amplitude is increasingly used in modern data acquisition. However, the conversion process always implies some loss of information due to amplitude quantization. Oversampling is the technique currently used to reduce this loss of accuracy. The error reduction can be performed by lowpass filtering the quantized signal, thus eliminating the high frequency components of the quantization error signal. This is the classical method used to reconstruct the analog signal from its oversampled and quantized version. This reconstruction scheme yields a mean squared error (MSE) inversely proportional to the oversampling ratio R. The fundamental question pursued in this thesis is the following: how much information is available in the oversampled and quantized version of a bandlimited signal for its reconstruction? In order to identify this information, it is essential to go back to the original description of quantization which is typically deterministic. We show that a reconstruction scheme fully takes this information into account
MLattice: A System For Signal Synthesis And Processing Based On ReactionDiffusion
 PROCESSING BASED ON REACTIONDIFFUSION. SCD THESIS, MIT
, 1994
"... This research begins with reactiondiffusion, first proposed by Alan Turing in 1952 to account for morphogenesis  the formation of hydranth tentacles, leopard spots, zebra stripes, etc. Reactiondiffusion systems have been researched primarily by biologists working on theories of natural pattern f ..."
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Cited by 5 (3 self)
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This research begins with reactiondiffusion, first proposed by Alan Turing in 1952 to account for morphogenesis  the formation of hydranth tentacles, leopard spots, zebra stripes, etc. Reactiondiffusion systems have been researched primarily by biologists working on theories of natural pattern formation and by chemists modeling dynamics of oscillating reactions. The past few years have seen a new interest in reactiondiffusion spring up within the computer graphics and image processing communities. However, reactiondiffusion systems are generally unbounded, making them impractical for many applications. In this thesis we introduce a bounded and more flexible nonlinear system, the "Mlattice", which preserves the natural patternformation properties of reactiondiffusion. On the theoretical front, we establish relationships between reactiondiffusion systems and paradigms in linear systems theory and certain types of artificial "neurallyinspired" systems. The Mlattice is closel...
UltraWideband AnalogtoDigital Conversion Via Signal Expansion
"... Abstract—We consider analog to digital (A/D) conversion, based on the quantization of coefficients obtained via the projection of a continuous time signal over a set of basis functions. The framework presented here for A/D conversion is motivated by the sampling of an input signal in domains which m ..."
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Cited by 5 (1 self)
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Abstract—We consider analog to digital (A/D) conversion, based on the quantization of coefficients obtained via the projection of a continuous time signal over a set of basis functions. The framework presented here for A/D conversion is motivated by the sampling of an input signal in domains which may lead to significantly less demanding A/D conversion characteristics, i.e., lower sampling rates and lower bit resolution requirements. We show that the proposed system efficiently parallelizes the analog to digital converter (ADC), which lowers the sampling rate requirements by increasing the number of basis functions on which the continuous time signal is projected, leading to a tradeoff between sampling rate reduction and system complexity. Additionally, the A/D conversion resolution requirements can be reduced by optimally assigning the available number of bits according to the variance distribution of the coefficients obtained from the signal projection over the new A/D conversion domain. In particular, we study A/D conversion in the frequency domain, where samples of the continuous signal spectrum are taken such that no time aliasing occurs in the discrete time version of the signal. We show that the frequency domain ADC overcomes some of the difficulties encountered in conventional timedomain methods for A/D conversion of signals with very large bandwidths, such as ultrawideband (UWB) signals. The proposed A/D conversion method is compared with conventional ADCs based on pulse code modulation (PCM). Fundamental figures of merit in A/D conversion and system tradeoffs are discussed for the proposed ADC. The signaltonoise and distortion ratios of the frequency domain ADC are presented, which quantify the impact of the most critical impairments of the proposed ADC technique. We also consider application to communications receivers, and provide a design example of a multicarrier UWB receiver. Index Terms—Analog to digital conversion (ADC), communications receiver, highspeed ADC, mixedsignal processing, quantization, signal expansion, ultrawideband. I.
Sigma Delta Quantization for Compressive Sensing
"... Compressive sensing is a new data acquisition technique that aims to measure sparse and compressible signals at close to their intrinsic information rate rather than their Nyquist rate. Recent results in compressive sensing show that a sparse or compressible signal can be reconstructed from very few ..."
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Cited by 4 (1 self)
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Compressive sensing is a new data acquisition technique that aims to measure sparse and compressible signals at close to their intrinsic information rate rather than their Nyquist rate. Recent results in compressive sensing show that a sparse or compressible signal can be reconstructed from very few measurements with an incoherent, and even randomly generated, dictionary. To date the hardware implementation of compressive sensing analogtodigital systems has not been straightforward. This paper explores the use of SigmaDelta quantizer architecture to implement such a system. After examining the challenges of using SigmaDelta with a randomly generated compressive sensing dictionary, we present efficient algorithms to compute the coefficients of the feedback loop. The experimental results demonstrate that SigmaDelta relaxes the required analog filter order and quantizer precision. We further demonstrate that restrictions on the feedback coefficient values and stability constraints impose a small penalty on the performance of the SigmaDelta loop, while they make hardware implementations significantly simpler.