Comparison of single- and double-sided pulse width modulated signals with non-linear predistortion

Class D amplifiers are based on a low-bit pulse width modulated (PWM) signal reconstructed through the lowpass characteristic of the loudspeaker. To create a PWM signal, a non-linear conversion from a standard pulse code modulated (PCM) signal has to be performed. The non-linear distortion created in this conversion process can be minimised by non-linear predistortion based on a Wiener-Hammerstein system. In this paper, we compare single and double-sided PWM conversion, whereby the former exhibits a higher resolution but also higher non-linearity compared to the latter. The trade-off between both approaches in creating a highly linear high performance class D audio amplifier is demonstrated by means of simulations and an implementation.