Compensation of Memory-Effects in PDM-based Transmitters for Digital Audio Broadcast

This paper examines existing amplitude modulation (AM) broadcast technology based on the envelope elimination and restoration (EER) amplification technique to determine its feasibility in accepting the new terrestrial digital audio broadcast (DAB) standards. When applying the hybrid AM DAB signals to EER amplifiers based on pulse duration modulation (PDM), digital signal processing algorithms are proposed to improve the overall performance of the system to meet the AM spectral mask. An investigation of the effects the various components of the EER amplifier have on the DAB signals is conducted to identify the most critical components in the system that contribute to the spectrum regrowth. It is found that the realistic envelope reconstruction filter in the envelope path of the EER amplifier requires specialized signal processing to extend the envelope path bandwidth. In particular, an LMS-based predistorter is proposed to improve filter frequency response and allow the DAB signalling to meet the required spectral mask