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 Nov 2017
TL;DR: The system architecture and the hardware complexity are parametrized on the number of look ahead steps, the Over Sampling Ratio (OSR) and the filter's order of the MSLA SDMs as well as on the balance between OSR, desirable frequency range span and Signal to Noise and Distortion ratio.
Abstract: An all-digital frequency synthesizer system architecture with single-bit digital output generating frequency signals while shaping the quantization noise outside of the useful frequency range is presented. The system uses two identical low-pass single-bit Multi-Step Look-Ahead Sigma-Delta modulators (MSLA SDMs) in a quadrature (I-Q) configuration driven by two multi-bit digital orthogonal sinusoidal signals generated by a direct digital synthesizer (DDS). MSLA SDMs operate in the baseband and their outputs are interleaved and frequency up-converted to generate the desirable high-frequency output signal. The system architecture and the hardware complexity of it are parametrized on the number of look ahead steps, the Over Sampling Ratio (OSR) and the filter's order of the MSLA SDMs as well as on the balance between OSR, desirable frequency range span and Signal to Noise and Distortion Ratio (SNDR).
Cites background or methods from "Understanding Delta-Sigma Data Conv..."
...In contrary, a DDS combined with a digital single-bit band-pass delta-sigma modulator (SDM) [3], can shape the quantization noise out of the desired frequency band and overcome the issue of the multi-bit DAC [4]....
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...Moreover, the output bandwidth range can be adjusted according to the OSR [3]....
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...The NTF of the frequency synthesizer at signal point yIF can be easily derived by using the transformation z → −z(2) to convert the low-pass NTF to band-pass [3], namely...
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01 Jan 2011
TL;DR: This chapter provides Simulink models and Matlab code for MASH, Multi-bit EFM and multi-bit SQ DDSMs, and gives an introduction to fractional-N synthesizers and the use of delta-sigma modulation in these systems.
Abstract: In this chapter, we review the principles of delta-sigma modulation We classify Delta-Sigma Modulators (DSMs) based on the types of signals they process and describe applications for each Digital DSMs (DDSM) are used in fractional-N frequency synthesizers and oversampling Digital-to-Analog Converters (DACs) We review the basic operation of a delta-sigma DAC Then we give an introduction to fractional-N synthesizers and the use of delta-sigma modulation in these systems We highlight the problem of spurious tones in DDSMs resulting from short cycle lengths and indicate how they degrade the performance of the synthesizers The chapter provides Simulink models and Matlab code for MASH, Multi-bit EFM and multi-bit SQ DDSMs
01 May 2019
TL;DR: This work presents a closed loop architecture for readout of Wheatstone bridge sensors which has inherent A/D-conversion and studied several design concerns in this system and explained how they could be overcome.
Abstract: We present a closed loop architecture for readout of Wheatstone bridge sensors. A key enabler of the proposed architecture is the floating bridge biasing technique. Thanks to this, the bridge's sense nodes can easily be read out in current mode. This current mode read-out in turn makes it very easy to convert the read-out front end amplifier of the bridge into an integrator. This integrator can then conveniently be used as the first integrator in a ΣΔ modulation feedback loop that can be set up around the sensor. This way we end up with a closed loop feedback system which has inherent A/D-conversion. We studied several design concerns in this system and explained how they could be overcome. Transistor level simulations confirm that the system can achieve adequate performance.
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