Multi Carrier Modulation Audio Power Amplifier with Programmable Logic

Theis Christiansen, Toke Meyer Andersen, Arnold Knott, Gerhard Pfaffinger, Michael A. E. Andersen

Research output: Chapter in Book/Report/Conference proceedingArticle in proceedingsResearchpeer-review


While switch-mode audio power amplifiers allow compact implementations and high output power levels due to their high power efficiency, they are very well known for creating electromagnetic interference (EMI) with other electronic equipment. To lower the EMI of switch-mode (class D) audio power amplifiers while keeping the performance measures to excellent levels is therefore of high interest. In this paper a class D audio amplifier utilising Multi Carrier Modulation (MCM) will be analysed, and a prototype Master-Slave Multi Carrier Modulated (MS MCM) amplifier has been constructed and measured for performance and out of band spectral amplitudes. The basic principle in MCM is to use programmable logic to combine two or more Pulse Width Modulated (PWM) audio signals at different switching frequencies. In this way the out of band spectrum will be lowered compared with conventional class D amplifiers. Analytically expressions, simulations and measurements result in reduced switching frequency amplitudes using MCM techniques. It is also shown that the Total Harmonic Distortion (THD) tends to be compromised compared to conventional class D amplifiers due to intermodulation products of the switching frequencies entering the audio band. Still, the MS MCM topology with two carrier signals shows a 6 dB reduction of the switching frequency amplitudes as well as THD across the audio band below 1% at 55 W output power open loop.
Original languageEnglish
Title of host publicationProceedings of the 37. AES International Conference
Publication date2009
Publication statusPublished - 2009
Event37th International AES Conference - Hillerød, Denmark
Duration: 28 Aug 200930 Aug 2009
Conference number: 37


Conference37th International AES Conference
Internet address


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