Effect of Demodulation Loop Non-Ideal Characteristics on the Pre-Distortion System

In this paper, the effects of non-ideal characteristics of the loop devices on the performance of pre-distortion were studied using the semi-physical simulation platform. First, a pre-distortion model and adaptive algorithm to be employed were presented, and then non-ideal characteristics of these devices and their effects on the transmission signal were analyzed. The effects of the non-ideal characteristics of different components on the adjacent channel power ratio (ACPR) and error vector magnitude (EVM) of transmitted signal were evaluated through a practical experimental platform. The results show that phase offset and jitter have a small effect on the system performance, while larger IQ imbalance and small number of quantization bits can cause much performance degradation. Some useful technical requirements are given for implementation consideration as well.