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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01 Jan 2011
TL;DR: This chapter investigates ΣΔ modulators and incremental A/D converters at low oversampling ratios and a sample 8th-order cascaded architecture is demonstrated for both topologies.
Abstract: This chapter investigates ΣΔ modulators and incremental A/D converters at low oversampling ratios. Both architectures have advantages at reduced OSRs; incremental A/D converters are able to achieve higher SQNR than ΣΔ modulators at oversampling ratios below 8, and ΣΔ modulators can attain better thermal noise performance than pipeline A/D converters at low OSRs. Both architectures are analyzed and a sample 8th-order cascaded architecture is demonstrated for both topologies.
01 Sep 2008
TL;DR: In this paper, an image-reject continuous-time (CT) quadrature bandpass (QBP) DS modulator using a tailored signal-transfer function (STF) design is presented.
Abstract: This paper presents the design of an image-reject continuous-time (CT) quadrature bandpass (QBP) DS modulator using a tailored signal-transfer-function (STF) design The quadrature delta-sigma noise shaping with polyphase filter implementations and strategic IF placement effectively improve image rejection internally The Fifth-order CT QBP DS modulator planned for WiMAX and Bluetooth standards, illustrates clearly the totally elimination of image generation and the correctly signal process This led to remove the baseband filter and PGA at the price of a very challenging ADC with merged-in cited functionalities So, less analog components, low power consumption and high performance for the low-IF receiver
Cites background from "Understanding Delta-Sigma Data Conv..."
...The structure is actually the extension, to complex form, of a similar structure used in higher-order real ∆Σ modulator [4]....
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TL;DR: In this paper, a 2nd-order multi-bit AD modulator with dynamic analog components for low power and high signal to noise and distortion (SNDR) application is presented.
Abstract: This paper presents an experimental prototype of 2nd-order multi-bit $$\Delta \Sigma $$
AD modulator with dynamic analog components for low power and high signal to noise and distortion (SNDR) application.
The integrators in the modulator are realized by ring amplifier without static current. Multi-bit quantizer and analog adder in the feed-forward modulator is realized by a passive-adder embedded successive approximation register analog to digital converter which consists of capacitor array and a dynamic comparator. The dynamic comparator does not dissipate static power at all when a pre-amplifier is not used. Proposed modulator is fabricated in TSMC 90 nm CMOS technology. Measurement results of the modulator dynamic range is over 84 dB. Measured peak SNDR = 77.51 dB, SNR = 80.08 dB are achieved for the bandwidth of BW = 94 kHz while a sinusoid differential $$-1$$
dBFS input is sampled at 12 MS/s. The total analog power consumption of the modulator is 0.37 mW while the supply voltage is 1.1 V.
Patent•
19 Apr 2012TL;DR: In this article, a delta-sigma-A/D converter with multiple integrators connected in cascade is presented, where the integrator positioned at the last stage is a passive integrator not using an amplifier circuit.
Abstract: The present invention relates to a delta-sigma-modulator and a delta-sigma-A/D converter. By speeding up the settling time constant of an integrator at the last stage with a simple configuration, the sampling frequency is sped up in the delta-sigma-modulator as a whole. Specifically, in the delta-sigma-modulator including multiple integrators connected in cascade, the integrator positioned at the last stage is a passive integrator not using an amplifier circuit, and one or more integrators positioned at stages preceding the last stage by one or more stages are active SC integrators using amplifier circuits and switched capacitor circuits, respectively. Also, each of the integrators performs integral calculation by alternately repeating a first operation phase to charge a sampling capacitor by sampling an input signal, and a second operation phase to perform a summing integration by transferring an electric charge charged in the sampling capacitor to an integration capacitor.
Dissertation•
01 Jan 2012
References
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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