双频段功率放大器的数字预失真研究

发布时间：2018-10-08 12:22

【摘要】：当前,同时支持多标准、多频段的通信系统正成为研究热点之一,作为通信系统中的一个重要组成部分,能够同时支持双带或多带工作的功率放大器是极具研究价值的课题之一。本文利用现有的数字预失真硬件平台,重点研究了基于新型多项式结构的双频段功放预失真模型和基于非线性滤波的双频段功放预失真模型,并给出了模型的架构方式、求解方法和实际硬件测试结果。在原本2D-DPD模型的基础上,改进了其中的高阶交叉多项式,引入新型的多项式结构。新型多项式结构的双频段预失真模型将2D-DPD模型中两维交叉高阶多项式运算降维成一维高阶多项式运算,使得模型更加易于在硬件上实现。非线性滤波模型则通过一阶非线性滤波网络来简化预失真结构,其运算中避免了高阶乘法。在基于数字预失真硬件测试平台的测试中,设定时间记忆特性M=2,新型多项式型和2D-DPD模型非线性阶数K=8,非线性滤波模型门限K1=K2=10、K3=K4=20,所提出的两种模型均可以达到与2D-DPD模型相同的预失真效果,间距140MHz、峰均比8dB的双带信号,在单带功率27～31dBm的情况下,预失真处理可使ACPR得到15dB的改善。非线性滤波模型大大减化了的双频段预失真模型的运算复杂度,其将模型系数存入查找表中,使得模型运算复杂度仅与时间记性特性有关,M=2时乘法运算仅需要18个。在数字预失真硬件测试平台上,基于FPGA实现了非线性滤波模型,并用以进行双频段预失真处理。FPGA定点化运算与MATLAB运算间的NMSE可达到-68dB的精度。经验证,基于FPGA实现的预失真模型可以达到与2D-DPD模型相一致的预失真效果。
[Abstract]:At present, multi-standard and multi-band communication systems are becoming one of the research hotspots, as an important part of communication systems, The power amplifier which can support two-band or multi-band operation at the same time is one of the most valuable research topics. Based on the existing digital predistortion hardware platform, this paper focuses on the dual-band predistortion model based on the new polynomial structure and the dual-band predistortion model based on nonlinear filtering, and gives the structure of the model. Solution method and actual hardware test results. Based on the original 2D-DPD model, the higher order crossover polynomial is improved and a new polynomial structure is introduced. The two-band predistortion model with a new polynomial structure reduces the dimension of the two-dimensional cross-high-order polynomial operation in the 2D-DPD model to one-dimensional high-order polynomial operation, which makes the model easier to be implemented in hardware. The nonlinear filter model simplifies the predistortion structure by the first order nonlinear filter network and avoids the high order multiplication. In the test based on digital predistortion hardware test platform, The two models can achieve the same pre-distortion effect as the 2D-DPD model, with the spacing of 140 MHz, the peak average ratio to the double band signal of 8dB, and the threshold of the nonlinear filtering model K _ (1) K _ (2) ~ (10) ~ (10) K _ (3) K _ (4) ~ (4) ~ (20). In the case of single band power 27~31dBm, ACPR can be improved by predistortion processing. The nonlinear filtering model greatly reduces the computational complexity of the dual-band predistortion model. The model coefficients are stored in the lookup table, which makes the computational complexity of the model only related to the time memory property and the multiplicative operation needs only 18. On the hardware testing platform of digital predistortion, the nonlinear filter model is implemented based on FPGA, and the NMSE between dual-band predistortion processing and MATLAB operation can reach -68dB accuracy. It is proved that the predistortion model based on FPGA can achieve the same predistortion effect as the 2D-DPD model.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN722.75

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