Book•
Understanding Delta-Sigma Data Converters
08 Nov 2004-
TL;DR: This chapter discusses the design and simulation of delta-sigma modulator systems, and some of the considerations for implementation considerations for [Delta][Sigma] ADCs.
Abstract: Chapter 1: Introduction.Chapter 2: The first-order delta-sigma modulator.Chapter 3: The second-order delta-sigma modulator.Chapter 4: Higher-order delta-sigma modulation.Chapter 5: Bandpass and quadrature delta-sigma modulation.Chapter 6: Implementation considerations for [Delta][Sigma] ADCs.Chapter 7: Delta-sigma DACs.Chapter 8: High-level design and simulation.Chapter 9: Example modulator systems.Appendix A: Spectral estimation.Appendix B: The delta-sigma toolbox.Appendix C: Noise in switched-capacitor delta-sigma data converters.
Citations
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20 May 2012
TL;DR: A second-order multi-bit hybrid continuous-time (CT) ΣΔ modulator has been implemented in a 65-nm CMOS technology and ensures jitter immunity granted by the use of multi-rate switched-capacitor (SC) DACs.
Abstract: A second-order multi-bit hybrid continuous-time (CT) ΣΔ modulator has been implemented in a 65-nm CMOS technology. The circuit ensures jitter immunity granted by the use of multi-rate switched-capacitor (SC) DACs. An auxiliary digital assistance technique reduces integrators output swing. The modulator provides 10.8 bits of resolution over a signal bandwidth of 1.1 MHz and a spurious free dynamic range (SFDR) of 78 dB. The chip draws 1.1 mW from a 1-V supply.
2 citations
Cites background from "Understanding Delta-Sigma Data Conv..."
...Since the sample and hold (S/H) in CT schemes is within the loop, the noise transfer function (NTF) filters the S/H inaccuracies, [1]....
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01 Jan 2017
2 citations
Cites background from "Understanding Delta-Sigma Data Conv..."
...On the other hand, ADCs that operate with a sampling rate much higher than the input signal bandwidth (fs >> 2fB) are called oversampling ADCs, which normally do not require a front-end antialiasing filter [52], [53]....
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...To improve the SNR, the quantization noise outside the signal bandwidth can be filtered out without degrading the desired signal, which is a popular technique in oversampling ADCs [35], [53]....
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TL;DR: It turns out that weak nonlinearity of the operational transconductance amplifier (OTA) used in the input integrator, in conjunction with the DAC pulse shape and OTA parasitics can greatly degrade the alias rejection of the modulator.
Abstract: Implicit anti-aliasing is a remarkable property of continuous-time delta–sigma modulators employing a time-invariant loop filter. It turns out that weak nonlinearity of the operational transconductance amplifier (OTA) used in the input integrator, in conjunction with the DAC pulse shape and OTA parasitics can greatly degrade the alias rejection of the modulator. The authors report and analyze this hitherto undiscovered mechanism. The theory is borne out by measurement results from a fourth-order single-bit filtering delta–sigma modulator designed in a 65-nm CMOS process. The alias-rejection of the modulator, which is expected to be about 160dB, is degraded to around 70dB by weak OTA nonlinearity and OTA parasitics.
2 citations
Cites background from "Understanding Delta-Sigma Data Conv..."
...DAC2 and Fc(z) form an FIR DAC that compensates the CT M for the delay introduced by the main FIR DAC (DAC1) [2]....
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...DAC1, which closes the fast 1/s path around the quantizer, is an RZ structure....
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...For a detailed analysis of the relative merits of these approaches, see [2]....
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...introduced by the main FIR DAC (DAC1) [2]....
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01 Jan 2010
TL;DR: In this paper, Theogarajan and his detailed and wholehearted guidance made the project progressing smoothly, and my academic endeavors here turned out to be very enjoyable and fruitful.
Abstract: iv ACKNOWLEDGEMENTS The dissertation belongs to many people who have directly or indirectly helped me achieve this goal. First, I sincerely appreciate my advisor, Prof. Luke Theogarajan, for his consistent financial and technical support in my research work at UCSB. His detailed and wholehearted guidance made the project progressing smoothly, and my academic endeavors here turned out to be very enjoyable and fruitful.
2 citations
References
More filters
TL;DR: Higher order modulators are shown not only to greatly reduce oversampling requirements for high-resolution conversion applications, but also to randomize the quantization noise, avoiding the need for dithering.
Abstract: Oversampling interpolative coding has been demonstrated to be an effective technique for high-resolution analog-to-digital (A/D) conversion that is tolerant of process imperfections. A novel topology for constructing stable interpolative modulators of arbitrary order is described. Analysis of this topology shows that with proper design of the modulator coefficients, stability is not a limitation to higher order modulators. Furthermore, complete control over placement of the poles and zeros of the quantization noise response allows treatment of the modulation process as a high-pass filter for quantization noise. Higher order modulators are shown not only to greatly reduce oversampling requirements for high-resolution conversion applications, but also to randomize the quantization noise, avoiding the need for dithering. An experimental fourth-order modulator breadboard demonstrates stability and feasibility, achieving a 90-dB dynamic range over the 20-kHz audio bandwidth with a sampling rate of 2.1 MHz. A generalized simulation software package has been developed to mimic time-domain behavior for oversampling modulators. Circuit design specifications for integrated circuit implementation can be deduced from analysis of simulated data. >
399 citations
TL;DR: It is shown that digital filters comprising cascades of integrate-and-dump functions can match the structure of the noise from sigma delta modulation to provide decimation with negligible loss of signal-to-noise ratio.
Abstract: Decimation is an important component of oversampled analog-to-digital conversion. It transforms the digitally modulated signal from short words occurring at high sampling rate to longer words at the Nyquist rate. Here we are concerned with the initial stage of decimation, where the word rate decreases to about four times the Nyquist rate. We show that digital filters comprising cascades of integrate-and-dump functions can match the structure of the noise from sigma delta modulation to provide decimation with negligible loss of signal-to-noise ratio. Explicit formulas evaluate particular tradeoffs between modulation rate, signal-to-noise ratio, length of digital words, and complexity of the modulating and decimating functions.
342 citations
TL;DR: This paper introduces a new method of analysis for deltasigma modulators based on modeling the nonlinear quantizer with a linearized gain, obtained by minimizing a mean-square-error criterion, followed by an additive noise source representing distortion components.
Abstract: This paper introduces a new method of analysis for deltasigma modulators based on modeling the nonlinear quantizer with a linearized gain, obtained by minimizing a mean-square-error criterion [7], followed by an additive noise source representing distortion components. In the paper, input signal amplitude dependencies of delta-sigma modulator stability and signal-to-noise ratio are analyzed. It is shown that due to the nonlinearity of the quantizer, the signal-to-noise ratio of the modulator may decrease as the input amplitude increases prior to saturation. Also, a stable third-order delta-sigma modulator may become unstable by increasing the input amplitude beyond a certain threshold. Both of these phenomena are explained by the nonlinear analysis of this paper. The analysis is carried out for both dc and sinusoidal excitations.
284 citations
TL;DR: Simple algebraic expressions for this modulation noise and its spectrum in terms of the input amplitude are derived and can be useful for designing oversampled analog to digital converters that use sigma-delta modulation for the primary conversion.
Abstract: When the sampling rate of a sigma-delta modulator far exceeds the frequencies of the input signal, its modulation noise is highly correlated with the amplitude of the input. We derive simple algebraic expressions for this noise and its spectrum in terms of the input amplitude. The results agree with measurements taken on a breadboard circuit. This work can be useful for designing oversampled analog to digital converters that use sigma-delta modulation for the primary conversion.
255 citations
01 Mar 1993
TL;DR: The modulator of a bandpass analog/digital (A/D) converter, with 63 dB signal/noise for broadcast AM bandwidth signals centered at 455 kHz, has been implemented by modifying a commercial digital-audio sigma-delta ( Sigma Delta ) converter.
Abstract: The modulator of a bandpass analog/digital (A/D) converter, with 63 dB signal/noise for broadcast AM bandwidth signals centered at 455 kHz, has been implemented by modifying a commercial digital-audio sigma-delta ( Sigma Delta ) converter. It is the first reported fully monolithic implementation of bandpass noise shaping and has applications to digital radio. >
211 citations