基于分段线性函数的功放模型及数字预失真应用

A power amplifier model based on piecewise-linear functions and digital predistortion application

为了克服通信系统中功率放大器的非线性和记忆效应,数字预失真技术成为研究的热点。提出一种基于分段线性函数的多项式模型,与广义记忆多项式模型相比,我们把多项式中的高阶项转换为分段求和项,消除了高阶相乘带来的不稳定性,同时由于分段阈值的存在,该模型的适用性和稳定性均有所提高。把功放模型应用于数字预失真结构中的实验结果表明:与广义记忆多项式模型相比,分段线性函数模型所需系数要少40%,邻信道功率比提高约1dB,归一化均方误差提高约8dB,因此该模型在数字预失真方面具有较好的效果。

Digital predistortion （DPD） becomes the most attractive technique in overcoming the nonlinearity and memory effects of power amplifiers （PAs） in communication systems. We propose a piecewise-linear memory polynomial （PWL-MP） model for DPD technique. Different from the generalized memory polynomial （GMP） model, our model converts the mulitplication of high order terms to the summation of PWL functions, in order to avoid the unstability of the muliplication of high order terms. As the threshold can be adjusted in the PWL-MP model, it is more flexible and accurate in the DPD technique. Experimental results show that the proposed model outperforms the GMP model while requiring less than 40% coefficients. The adjacent channel power ratio （ACPR） and the normalized mean square error （NMSE） can be improved by ldB and 8 dB respectively. So the PWL-MP model can achieve a relatively better performance in the DPD technique.