Digital Predistortion Function Synthesis using Undersampled Feedback Signal
Digital Predistortion Function Synthesis using Undersampled Feedback Signal
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DOI：
10.1109/lmwc.2016.2605500
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发表时间：
2016-10
影响因子：
3
通讯作者：
Hai Huang;P. Mitran;S. Boumaiza
中科院分区：
文献类型：
--
作者：
Hai Huang;P. Mitran;S. Boumaiza
本文提出了一种利用欠采样反馈信号合成数字预失真（DPD）函数的新方法。首先，推导出可适应反馈信号欠采样的DPD更新算法的表达式。这包括迭代地识别DPD函数系数的直接学习算法。然后，延迟估计和对齐算法，采用分数延迟滤波器估计和补偿的非整数延迟之间的采样输入和欠采样输出信号的功率放大器（PA）。新提出的方法被发现具有可比的线性化能力相比，传统的基于全速率的间接学习DPD，即使具有显着欠采样的反馈信号。例如，它被成功地应用于线性化由高达80 MHz带宽的宽带调制信号驱动的20 W GaN Doherty PA，并在使用以80个复数MSP采样的复数反馈信号线性化后产生-49 dBc的ACLR，而传统采样需要400个复数MSP。
This letter presents a new approach to synthesize the digital predistortion (DPD) function using an undersampled feedback signal. First, an expression for the DPD update algorithm that accommodates undersampling of the feedback signal is derived. This includes a direct learning algorithm that iteratively identifies the DPD function coefficients. Then, a delay estimation and alignment algorithm that employs a fractional delay filter is presented for estimating and compensating the non-integer delay between the sampled input and undersampled output signals of the power amplifier (PA). The new proposed approach is found to have comparable linearization capability compared to a conventional full-rate based indirect-learning DPD, even with a significantly undersampled feedback signal. For instance, it was successfully applied to linearize a 20 W GaN Doherty PA driven by a wideband modulated signal of up to 80 MHz bandwidth, and yield an ACLR of -49 dBc after linearization using a complex feedback signal sampled at 80 complex MSPs as opposed to 400 complex MSPs that would be required for conventional sampling.