Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Research Article Distortion-Free 1-Bit PWM Coding for Digital Audio Signals | Hindawi Publishing Corporation EURASIP Journal on Advances in Signal Processing Volume 2007 Article ID 94386 12 pages doi 2007 94386 Research Article Distortion-Free 1-Bit PWM Coding for Digital Audio Signals Andreas Floros1 and John Mourjopoulos2 1 Department of Computer Science Ionian University Plateia Tsirigoti 7 49 100 Corfu Greece 2 Audio Technology Group Department of Electrical and Computer Engineering University of Patras 265 00 Rio Patras Greece Received 15 June 2006 Revised 1 December 2006 Accepted 13 March 2007 Recommended by Sven Nordholm 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 nonharmonic 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 . X4 resulting to typical PWM clock rates of 90 MHz. Copyright 2007 A. Floros and J. Mourjopoulos. This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited. 1. INTRODUCTION Over the last decades the use of 1-bit audio signals
