Analysis and simulation of HPAs´ effects on satellite OFDM systems

The paper presents a detailed theoretical analysis and simulation of the performance degradation in satellite Orthogonal Frequency Division Multiplexing (OFDM) system when the OFDM signals are passed through a non-linear High Power Amplifier (HPA). The HPA is modeled as Traveling Wave Tube Amplifier (TWTA) Saleh model. Firstly, Basic characteristics of OFDM signals after HPA are analyzed. Secondly, different performances such as bit error rate (BER), total degradation (TD) are simulated based on the models of HPA and the satellite OFDM communication system. In addition, performances of different baseband modulations (BPSK, QPSK, 16APSK) are compared conveniently. The results show that: (1) the nonlinearity of HPA brings OFDM signal with constellation scattering and spectral regrowth; (2) amplitude reduction, phase rotation of signals and BER performance of system exaggeration are also caused by TWTA. (3) although spectral efficiency of 16APSK is higher than BPSK and QPSK, its BER performance is much poorer than that of them.