Impact of HPA nonlinearity on downlink signal degradation in satellite communications

In this paper an impact of high power amplifier (HPA) nonlinearity on downlink signal constellation in satellite communications is analyzed. The variations in the signal envelope affecting the amplitude and phase of the output signal referred to as amplitude (AM-AM) and phase (AM-PM) envelope characteristics due to HPA nonlinearity, are computed according to the Saleh´s model. Different values of HPA back-off level are used in simulation process, moving the HPA operating point from moderate to severe nonlinearity region. 16-QAM constellation format is proposed, while the input and output signal constellation is computed for different values of back-off level, showing phase rotation and amplitude compression in the output signal constellation.