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无线通信系统中的高阶调制信号具有频带利用率高,能够有效缓解频谱资源紧张的现状的优势,而非恒包络的高阶调制信号经系统中的功率放大器时会发生非线性失真,严重恶化了通信系统的性能。随着数字信号处理(DSP)技术的高速发展,基带自适应数字预失真补偿技术是实现功放线性化最有效的方式之一。本文以高阶正交振幅调制(QAM)信号为对象,建立了功放记忆非线性失真的模型,利用误差矢量幅度(EVM)和邻近信道功率比(ACPR)两个优化指标确定了预失真结构的记忆深度和非线性阶数,并基于确定的预失真结构,利用RLS自适应算法来获取预失真器补偿参数。仿真结果表明,经过预失真补偿的星座图和功率谱带外再生得到了较好的矫正,星座图EVM改善值达到56.7%,信号功率谱带外再生抑制平均提升了2.89d B,系统线性化性能非常理想。
The high-order modulated signal in wireless communication system has the advantages of high frequency band utilization and effective mitigation of the shortage of spectrum resources. Non-constant-amplitude high-order modulated signal is nonlinearly distorted by the power amplifier in the system. Worsen the performance of the communication system. With the rapid development of digital signal processing (DSP) technology, baseband adaptive digital predistortion compensation technology is one of the most effective ways to achieve PA linearization. In this paper, a high-order Quadrature Amplitude Modulation (QAM) signal is taken as an object to establish a nonlinear distortion model of power amplifier memory. Two optimization indexes of error vector magnitude (EVM) and adjacent channel power ratio (ACPR) Memory depth and nonlinear order, and based on the determined predistortion structure, using RLS adaptive algorithm to obtain the predistorter compensation parameters. The simulation results show that the constellation after pre-distortion compensation and power spectrum regeneration are better corrected, the constellation EVM improved value reached 56.7%, the signal power spectrum out-of-band regeneration increased by 2.89d B on average, the system linearization Performance is very good.