In recent years the rapid growth of the number of users in mobile communication networks led to the development of third generation standards like UMTS. The modulation and the multiple user access methods where designed for high spectral efficiency. This leads to strong fluctuations of the power envelope transmitted by the UMTS Base-Stations and therefore to nonlinear effects caused by power amplifiers. Because these devices are the most cost intensive, it is desirable to operate the amplifiers close to their compression points. The main problem is the pronounced dynamic nonlinear behaviour of the amplifier, combined with fluctuations in the envelope in the transmission signal. Several state-of-the-art methods like Feed-Forward are used in today's power amplifiers, but are expensive hardware items. The goal of this work is the investigation of more flexible and powerful linearization methods called Digital Predistortion. This method aims at inverting the dynamic nonlinearity of the whole transmitter chain in the digital baseband.
|Effective start/end date||1/07/03 → 31/01/09|