联合深度限幅的自适应数字预失真技术研究

Research on the adaptive digital pre-distortion technique combined with deep clipping

提出联合峰均比降低技术(PAPR)和数字预失真技术(DPD)对国标地面数字电视广播(DTMB)系统功率放大器进行线性化处理.PAPR降低技术采用深度限幅滤波,计算复杂度低.DPD方法则是采用基于查找表的预失真技术,为提高查找表的收敛速度,自适应算法采用变步长的RASCAL算法,并在查询表收敛过程中,对查找表进行拉格朗日内插.仿真结果表明,使用深度限幅与预失真联合技术时功放效率可以得到较大提高.以功率回退值为指标,与单独使用预失真技术时的功放效率相比,可以减少功率回退4.5 dB,ACPR可以达到-45 dBc.与传统的联合技术相比,ACPR可以改善4 dB.

In this paper, digital pre - distortion （DPD） is combined with peak -to- average power ratio （PAPR） reduction to deal with the high power amplifier （HPA） nonlinear problem in digital ter- restrial broadcast （DTMB） system. The PAPR reduction method is based on the deep clipping and fil- tering technique with low computational complexity, while the DPD method consists of modeling the behavior of HPA using a look -up -table （LUT）. To accelerate the convergent rate of LUT, the pre -distortion algorithm is RASCAL algorithm with variable error- adjusting steps, and Lagrange inter- polation is used in the convergent process. The simulation results show that the combination of deep clipping and DPD can enhance the HPA efficiency greatly which is evaluated by IBO value. Compa- ring with the scheme only with DPD technique, the IBO value of the combined scheme can reduce 4.5 dB. The ACPR can reach - 45 dBc. The ACPR of DPD combined with deep clipping is better than the traditional combination technique for 4 dB.