Abstract
Abstract. In this paper a new filter design concept is proposed and implemented which takes into account the complex loudspeaker impedance. By means of techniques of broadband matching, that has been successfully applied in radio technology, we are able to optimize the reconstruction filter to achieve an overall linear frequency response. Here, a passive filter network is inserted between source and load that matches the complex load impedance to the complex source impedance within a desired frequency range. The design and calculation of the filter is usually done using numerical approximation methods which are known as Real Frequency Techniques (RFT). A first approach to systematic design of reconstruction filters for class-D amplifiers is proposed, using the Simplified Real Frequency Technique (SRFT). Some fundamental considerations are introduced as well as the benefits and challenges of impedance matching between class-D amplifiers and loudspeakers. Current simulation data using MATLAB is presented and supports some first conclusions.
Highlights
Introduction and motivationThe development of audio technology in recent years is primarily characterized by more efficient and compact power components and systems
The signal can be amplified by the switching stage and it has to be decoded by a demodulator
This contribution deals with a new method of class-D output filter design which allows the designer to take into account the given impedance for an optimum overall frequency response
Summary
The development of audio technology in recent years is primarily characterized by more efficient and compact power components and systems. The audio signal has to be initially encoded by a modulator (e.g. pulse width modulation). The signal can be amplified by the switching stage and it has to be decoded by a demodulator (reconstruction filter). In consequence of committing these effects, the frequency response of the filter will no longer be linear in the audio band and will distort the signal. This contribution deals with a new method of class-D output filter design which allows the designer to take into account the given impedance for an optimum overall frequency response. Some basic preliminaries and specifications have to be made first
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