卫星通信中16QAM 信号的数字预失真研究

摘要

Nonlinear distortion occurs when high-order modulation signals pass through a power amplifier and linear compensation is required for the power amplifier.Power back-off is the simplest and most direct method,but the efficiency of power amplifier is not high.Thanks to the development of DSP (Digital Signal Processing)technology, digital pre-distortion has become one of the most effective ways to compensate for nonlinear distortion caused by power amplifiers.To a certain extent,this has promoted the application of high-order modulation signals in satellite communication and has relaxed the problem of spectrum resource shortage.Choosing 1 6QAM signal as the research object,we focus on the impact of two key factors of the pre-distortion model, nonlinearity order and memory depth,on pre-distortion performance.Simulation results show that memory depth has greater impact on the pre-distortion performance,when compared to nonlinearity order.Furthermore, the combination of power back-off method and the digital pre-distortion method yields better pre-distortion performance.%高阶信号通过功放时发生非线性失真，需对功放进行线性化补偿，功率回退法是最简单直接的线性化方法，但功放效率不高。数字信号处理技术的发展使得数字预失真技术成为补偿功放失真最有效的方式之一，在一定程度上促进了高阶调制信号在卫星通信中的应用，缓解频谱资源紧张问题。以16QAM 信号为对象，着重研究了预失真器模型的两个关键因子———非线性阶数和记忆深度———对预失真性能的影响。仿真结果表明，相较于非线性阶数，记忆深度对预失真性能的影响更大；而且功率回退法和数字预失真方法的结合使用可以取得更好的预失真效果。