On the Myth of Pulse Width Modulated Spectrum in Theory and Practice

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Abstract

Switch-mode audio power amplifiers are commonly used in sound reproduction. Their well known drawback is the radiation of high frequent energy, which can disturb radio and TV receivers. The designer of switch-mode audio equipment therefore needs to make arrangements to prevent this coupling which would otherwise result in bad audio performance. A deep understanding of the pulse width modulated (PWM) signal is therefore essential, which resulted in different mythic models as pulse, trapezoidal or Double Fourier Series (DFS) representations in the past. This paper will clarify these theoretical approaches by comparing them with reality from both the time and the frequency domain perspective. For validation a switch-mode audio power amplifier was built, delivering the contents material with less than 0.06 % distortion across the audio band at 50 W. The switch-mode signals have been evaluated very precisely in time and spectral domain to enlighten the assumptions about the PWM spectra and decrypt this myth.
Original languageEnglish
Title of host publication126th Audio Engineering Society Convention
PublisherUniversity of Strathclyde
Publication date2009
Pages7799
ISBN (Print)978-0-937803-67-7
Publication statusPublished - 2009
Event126th Audio Engineering Society Convention - Munich, Germany
Duration: 7 May 200910 May 2009
http://www.aes.org/events/126/

Conference

Conference126th Audio Engineering Society Convention
CountryGermany
CityMunich
Period07/05/200910/05/2009
Internet address

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