| This paper studies digital predistortion of RF power amplifier. Inherent nonlinearcharacteristics of RF power amplifier will lead to high bit error rate and severe adjacentchannel interference. Orthogonal Frequency Division Multiplexing (OFDM) technology iswidely used in the third generation mobile communication systems, but high peak to averagepower ratio (PAPR) makes it more sensitive than the other signals to the nonlinearity ofpower amplifier, so linearization of RF power amplifier is particularly important. Among allthe linearization techniques, digital predistortion technology is most promising with its highstability, better linearization effect and adaptive performance.Firstly, this paper introduces the nonlinear performance of RF power amplifier, and thecharacteristics of RF signal in PC7203, which is a single development board for a wirelessbase station, then analyzes the feature of the RF power amplifier behavioral models. Later,the commonly used adaptive algorithms for digital predistortion technology are described, thepredistortion principle of look-up table(LUT) method, polynomial method and neuralnetworks method are introduced.The characteristics of the power amplifier in OFDM system are tested and its parametersare extracted, by Signal Source SMU200A and Analyzer R&S FSQ, in order to set up asuitable behavior model of power amplifier for digital predistortion process. And thepolynomial model was chosen for research of power amplifier in this article.Moreover, look-up table method and polynomial method for predistortion are realizedand the results are analyzed. Combining high accuracy of LUT method with the advantageof less storage space of polynomial method, a joint method based on LUT andpolynomial method is concluded with an optimal segmentation method, optimum number ofsegments is obtained by simulation. Finally, the joint predistortion method based on theoptimal number of segments is proved better than LUT and polynomial method. |
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