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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06 May 2012
TL;DR: A new RoF transmission scheme employing Envelop Pulse-Width Modulation (EPWM) transmitter has been proposed to efficiently suppress the impact of RoF channel nonlinearity on OFDM signals.
Abstract: Radio-over-Fiber (RoF) technology enables low-loss distribution of RF signals over optical fiber, which contributes much for spreading broadband wireless access services into in-building areas and outdoor dead-spots. However, current broadband wireless access systems employ OFDM schemes and suffer from nonlinear distortion of the RoF channel due to nonlinearity inherent in Electrical to Optical (E/O) conversion. In this paper, a new RoF transmission scheme employing Envelop Pulse-Width Modulation (EPWM) transmitter has been proposed to efficiently suppress the impact of RoF channel nonlinearity on OFDM signals. This idea is executed in a typical RoF channel that uses a Mach-Zehnder modulator as its E/O convertor. It is proved by both simulation and experiment that the EPWM-RoF scheme can achieve linear transmission of OFDM signal via nonlinear RoF channel.
4 citations
Cites background from "Understanding Delta-Sigma Data Conv..."
...In order to reduce the effects, the input signal should be oversampled with a higher order ratio so that the quantization noise can be sufficiently suppressed by noise shaping property of the Δ − Σ modulator [9]....
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01 Nov 2009
TL;DR: In this paper, the authors propose a new technique that tunes the center frequency of a mismatch noise transfer function while using an arbitrary mismatch shaping algorithm using a programmable bandpass ΔΣ converter.
Abstract: Many radio applications require the use of programmable bandpass ΔΣ converter. In the digital-to-analog converter (DAC) used within a ΔΣ converter, non-linearities created by DAC element mismatch error can be spectrally shaped to fall outside the signal band. The mismatch shapers within these converters thus also need to be programmable in order to follow the signal band. This paper proposes a new technique that tunes the center frequency of a mismatch noise transfer function while using an arbitrary mismatch shaping algorithm.
4 citations
Cites methods from "Understanding Delta-Sigma Data Conv..."
...Mismatch shaping is one technique for alleviating the effects of mismatch errors [4] [5]....
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01 Oct 2018
TL;DR: This paper reviews the authors’ group research results of data-weighted averaging (DWA) algorithm for multi-bit ΔΣADC/DAC/TDC and also dithering techniques for ΔηDAC for limit cycle reduction and also investigates limit cycle suppression techniques in ΔδΣDAC.
Abstract: This paper reviews the authors’ group research results of data-weighted averaging (DWA) algorithm for multi-bit ΔΣADC/DAC/TDC and also dithering techniques for ΔΣ ADC/DAC for limit cycle reduction. When a multi-bit internal DAC or digital-to-time converter (DTC) is used inside a modulator, nonlinearities of the DAC/DTC are not noise-shaped and the SNR of the ΔΣADC/DAC/TDC degrades. To overcome this problem, we investigate several algorithms to noise-shape the DAC/DTC nonlinearities. Also we investigate limit cycle suppression techniques in ΔΣDAC. Then we discuss their generalization.
4 citations
Cites background from "Understanding Delta-Sigma Data Conv..."
...Introduction Multi-bit ∆Σ modulators are effective for low power because the requirements for operational amplifiers there are relaxed [1, 2]....
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28 Sep 2020
TL;DR: The Signal Leakage Function (SLF) is proposed, to optimize the architecture, and hence improving DR, of wide-bandwidth, low-OSR continuous-time (CT) multi-stage noise-shaping (MASH) ΔΣM and provides new insights on finding the key parameters which influence the inter-stage signal leakage.
Abstract: This paper analyzes the error mechanisms that limit the dynamic range (DR) of wide-bandwidth, low-OSR continuous-time (CT) multi-stage noise-shaping (MASH) ΔΣM and proposes a tool, the Signal Leakage Function (SLF), to optimize the architecture, and hence improving DR. The SLF provides new insights on finding the key parameters which influence the inter-stage signal leakage and thus the inter-stage gain (IG). These insights would lead not only to increasing the overall dynamic range in a very power-efficient way, but also decreasing the performance sensitivity to mismatches and other variations.
4 citations
TL;DR: A modified frequency-domain approach to identify the ARMAX modulator starting from its input-output data, illustrated on both low-pass and bandpass ¿¿ modulators, showing an excellent agreement between the theoretical and estimated transfer functions.
Abstract: Sigma-delta modulators are becoming increasingly more popular in electronic circuits. They are characterized via their signal and noise transfer functions (STF and NTF). This linearized model is basically an autoregressive moving average model with exogenous inputs (ARMAX) model, which is used during the design of the modulator. Hence, the pole/zero locations of its transfer functions give valuable information about the system. The identification of the poles and zeros from input/output data enables the verification of the complete ?? modulator and can be used on actual measurements where the internal signals are not accessible. The identification of ARMAX models from input-output data is well studied in the literature under conditions that are generally met in control applications. However, ?? modulators are designed such that these general assumptions are violated. This paper gives an overview of the properties of ?? modulators and compares the pros and cons of both time- and frequency-domain identification techniques for ARMAX systems. Then, it discusses a modified frequency-domain approach to identify the ?? modulator starting from its input-output data. The technique is illustrated on both low-pass and bandpass ?? modulators, showing an excellent agreement between the theoretical and estimated transfer functions.
4 citations
Cites background or methods from "Understanding Delta-Sigma Data Conv..."
...The zeros of the NTF are located in the signal band (between fc − fs/256 and fc + fs/256) according to the optimal pole location described in [1]....
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...9 shows the output power spectrum of the simulations and the noise spectrum predicted by linear system theory [1]....
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...The NTF can also contain transmission zeros by construction [1], [5], [6]....
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...6 shows the output power spectrum and the noise spectrum as predicted by linear system theory [1]....
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...The model equation of this system is then equal to [1], [5], [6]...
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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