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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12 May 2008
TL;DR: This work studies the joint optimization of the quantizer and the spatial decision feedback equalizer for the flat multi-input multi-output (MIMO) channel with quantized outputs based on a minimum mean square error (MMSE) approach.
Abstract: We study the joint optimization of the quantizer and the spatial decision feedback equalizer (DFE) for the flat multi-input multi-output (MIMO) channel with quantized outputs. Our design is based on a minimum mean square error (MMSE) approach, taking into account the effects of quantization. Our derivation does not make use of the assumption of uncorrelated white quantization errors and considers the correlations of the quantization error with the other signals of the system. Through simulation, we compare the new DFE to the conventional spatial DFE operating on quantized data in terms of uncoded BER.
19 citations
Cites background from "Understanding Delta-Sigma Data Conv..."
...In fact, in order to reduce circuit complexity and save power and area, low resolution ADCs have to be employed [4]....
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TL;DR: This paper introduces two new techniques to enhance both efficiency and signal bandwidth in delta-sigma-based transmitters by using a controlled filtering on in-band quantization noise along with QNR technique, the bandwidth of the signal and efficiency are increased simultaneously without losing as much linearity.
Abstract: This paper introduces two new techniques to enhance both efficiency and signal bandwidth in delta-sigma-based transmitters At first step, a technique called quantization noise reduction (QNR), is introduced to enhance the coding efficiency By filtering out part of the quantization noise in the whole band of the signal, while the signal envelope is maintained almost constant, the coding efficiency is improved without imposing any additional nonlinearity or distortion to the system By utilizing this technique for an orthogonal frequency division multiplexing (OFDM) signal with 125-MHz bandwidth and 80 times oversampling, with 81-dB peak-to-average power ratio (PAPR), the coding efficiency is improved from 88% to 145% while the signal-to-noise distortion ratio (SNDR) of the system remains 43 dB In the next step by using a controlled filtering on in-band quantization noise along with QNR technique, the bandwidth of the signal and efficiency are increased simultaneously without losing as much linearity The second technique is called quantization noise reduction with in-band filtering or (QNRIF) QNRIF is applied on an OFDM signal with 125-MHz bandwidth, with the same PAPR and only 16 times oversampling The result for the coding efficiency is improved from 77% to 187% with 41-dB SNDR
19 citations
Cites methods from "Understanding Delta-Sigma Data Conv..."
...2 depicts first-order and second-order DSMs used for this analysis [17]....
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01 Jan 2010
TL;DR: In this paper, a parametric array consisting of 576 ultrasonic transducers controlled individually by using high speed 1-bit signal processing is presented, which is able to control the angle of an audio beam by creating a synthesized surface wavefront.
Abstract: Parametric loudspeakers are known for a very sharp directivity due to their ultrasonic carrier wave. A desired audio signal modulated onto this carrier wave is reproduced along the beam by intrinsic non-linearity of the air. Because of this directivity, parametric speakers provide for distinguished audio applications. In this paper we present our parametric array consisting of 576 ultrasonic transducers controlled individually by using high speed 1-bit signal processing. We are able to control the angle of an audio beam by creating a synthesized surface wavefront. Furthermore, we present an experiment where multiple independent audio beams are emitted from the single parametric loudspeaker.
19 citations
TL;DR: The proposed DT modeling technique is derived from the impulse-invariant transform and is applicable to arbitrary-order lowpass and bandpass CT DeltaSigma modulators, with single-bit or multibit feedback digital-to-analog converters (DACs) employing delayed return- to-zero (RZ) or non-return-to thezero (NRZ) rectangular pulses.
Abstract: This paper proposes a simple discrete-time (DT) modeling technique for the rapid, yet accurate, simulation of the effect of clock jitter on the performance of continuous-time (CT) DeltaSigma modulators. The proposed DT modeling technique is derived from the impulse-invariant transform and is applicable to arbitrary-order lowpass and bandpass CT DeltaSigma modulators, with single-bit or multibit feedback digital-to-analog converters (DACs) employing delayed return-to-zero (RZ) or non-return-to-zero (NRZ) rectangular pulses. Its accuracy is independent of both the power spectrum of the clock jitter and the loop transfer function of the DeltaSigma modulator. The proposed DT modeling technique is validated (for both independent and accumulated clock-jitter errors) against accurate simulations in SIMULINK, using behavioral blocks developed to directly simulate RZ or NRZ DACs with clock jitter. It is subsequently applied to various CT DeltaSigma modulator architectures (low- pass and bandpass, with single-bit and multibit DACs) to study the relative effectiveness of different feedback-DAC pulsing schemes (NRZ, RZ, RZ with fixed on-time, and RZ with fixed off-time) in minimizing the modulator sensitivity to clock jitter. The performance of each architecture is compared as a function of clock jitter, thereby offering a valuable reference for selecting a rectangular feedback-DAC pulse shape when designing CT DeltaSigma analog-to-digital converters.
19 citations
Additional excerpts
..., ) for optimal noise-shaping performance [12]....
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...However, for ease of implementing the digital mixers after the bandpass modulator [12], the sampling frequency is typically selected as ....
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...However, in a bandpass modulator, the input signal is typically sampled at for ease of implementing the digital mixers after the bandpass modulator [12]....
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TL;DR: This paper treats the chopped integrator as a linear periodically time-varying system, and exploits the adjoint (inter-reciprocal) network concept to simplify the analysis of aliasing effects in such an integrator.
Abstract: Chopping is a commonly used technique to eliminate flicker noise in amplifiers. We investigate the use of chopping in the input integrator of a continuous-time oversampling ( $\Delta \!\Sigma $ ) converter. Unlike an amplifier, the integrator in a continuous-time delta-sigma modulator is subject to out-of-band signals that are several orders of magnitude higher than the (desired) in-band component. This necessitates a careful analysis of frequency translation effects in a chopped integrator. This paper treats the chopped integrator as a linear periodically time-varying system, and exploits the adjoint (inter-reciprocal) network concept to simplify the analysis of aliasing effects in such an integrator. Simulation results that confirm the theory are given.
19 citations
Cites background from "Understanding Delta-Sigma Data Conv..."
...However, as shown in [9] and [10], this is only true when...
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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