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Distortion-Free 1-Bit PWM Coding for Digital Audio Signals

Abstract

Although uniformly sampled pulse width modulation (UPWM) represents a very efficient digital audio coding scheme for digital-to-analog conversion and full-digital amplification, it suffers from strong harmonic distortions, as opposed to benign non-harmonic artifacts present in analog PWM (naturally sampled PWM, NPWM). Complete elimination of these distortions usually requires excessive oversampling of the source PCM audio signal, which results to impractical realizations of digital PWM systems. In this paper, a description of digital PWM distortion generation mechanism is given and a novel principle for their minimization is proposed, based on a process having some similarity to the dithering principle employed in multibit signal quantization. This conditioning signal is termed "jither" and it can be applied either in the PCM amplitude or the PWM time domain. It is shown that the proposed method achieves significant decrement of the harmonic distortions, rendering digital PWM performance equivalent to that of source PCM audio, for mild oversampling (e.g.,) resulting to typical PWM clock rates of 90 MHz.

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Correspondence to Andreas Floros.

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Open Access This article is distributed under the terms of the Creative Commons Attribution 2.0 International License (https://doi.org/creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Floros, A., Mourjopoulos, J. Distortion-Free 1-Bit PWM Coding for Digital Audio Signals. EURASIP J. Adv. Signal Process. 2007, 094386 (2007). https://doi.org/10.1155/2007/94386

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Keywords

  • Pulse Width
  • Quantum Information
  • Generation Mechanism
  • Audio Signal
  • Pulse Width Modulation