Effect of demodulator errors on predistortion linearization

Any errors in a linearization system for power amplifiers will affect linearization results. In this paper the effect of the demodulator errors on a few adaptive predistortion techniques is studied. The investigations are focused on the complex gain predistorter and the mapping predistorter. The analyses and simulations show that in the complex gain predistorter only a DC offset will affect the adjacent channel interference (ACI). Gain imbalance and phase imbalance of the demodulator have no effect on the ACI in the complex gain predistorter system. In the mapping predistorter system, although the predistorter was also misadjusted because of errors, the ACI will not be deteriorated. But due to these errors, linear distortions will emerge in both systems and bit error rate (BER) of both systems will be degraded. The conclusions obtained in this paper can be used to guide the predistorter design. According to these guidelines the design process can be simplified and the ACI can be improved