面向高阶调制的5G 宽带射频功放数字预失真技术

在第5 代无线通信系统(5G) 中, 射频(RF) 功放(PAs) 有着严重的非线性失真和强记忆效应, 尤其是对于采用复杂的高阶调制系统, 如16QAM、64QAM 等。为了研究和提高宽带RF PAs 的线性化能力, 提出基于先进设计系统(advanced design system, ADS) 设计的宽带RF PAs, 工作的中心频率为3.55 GHz, 采用记忆多项式(MP) 模型构建数字预失真器, 模型的归一化均方误差(NMSE) 指标可达??33:28 dB。最后, 采用带宽为100 MHz 的16QAM或64QAM 高阶调制的5G 新空口(new radio, NR) 信号, 信号最大幅度值为9.899 dB, 对中心频率为3.55 GHz 的RF PAs 进行预失真仿真验证。仿真结果表明, 在16QAM 调制方式下, 邻信道功率比(ACPR) 可分别改善20.13 dB 和20.05 dB; 在64QAM 调制方式下, ACPR 可分别改善18.35 dB 和19.08 dB。实验测试结果表明, 在16QAM 调制方式下, ACPR 分别改善15.81 dB 和16.40 dB; 在64QAM 调制方式下, ACPR 分别改善15.44 dB 和15.82 dB。说明基于MP 的数字预失真器对基于ADS 的RF PAs 的非线性具有明显的抑制作用。因此基于MP 模型的数字预失真器可用于所提RF PAs 的线性化, 且采用16QAM 调制方式比基于64QAM 调制方式的预失真能力更强。

Investigation on Digital Predistortion Technique of 5G Wideband RF Power Amplifiers for High-Order Modulation

In the fifth-generation wireless communication system (5G), RF power amplifiers (PAs) exhibit severe non-linear distortion and pronounced memory effects, particularly when employed in complex high-order modulation schemes such as 16QAM and 64QAM. To investigate and enhance the linearization capability of wideband RF PAs, a wideband RF PAs design based on the advanced designsystem (ADS) is proposed. Operating within a central frequency of 3.55 GHz, the memory polynomial (MP) model is employed to construct a digital pre-distorter, achieving a normalized mean square error (NMSE) metric of ??33:28 dB. Finally, simulation-based verification is conducted using 5G new radio (NR) signals employing 16QAM or 64QAM high-order modulation with a bandwidth of100 MHz and a signal peak amplitude of 9.899 dB, centered at a frequency of 3.55 GHz RF PAs. The simulation results demonstrate that under 16QAM modulation, the adjacent channel power ratio (ACPR) can be improved by 20.13 dB and 20.05 dB, respectively. For 64QAM modulation, ACPR improvement rates of 18.35 dB and 19.08 dB are observed. Experimental test results show that ACPRimproves by 15.81 dB and 16.40 dB in 16QAM modulation mode and 15.44 dB and 15.82 dB in 64QAM modulation mode, respectively, which underscores the evident suppressive effect of the MP-based digital pre-distorter on the non-linearity of the ADS-based RF PAs. Consequently, digital pre-distorter based on MP model can be used for linearization of the proposed RF PAs and the pre-distortioncapability is better with 16QAM modulation than 64QAM based modulation.