摘要
随着无线通信技术的飞速发展，射频功率放大器起着越来越重要的作用。出于对更高频谱利用率和更高功率效率的需求，线性调制技术和高效率的射频功率放大器得到了广泛应用。但包络变化的信号经过非线性射频功率放大器后会产生互调失真，造成严重的码间干扰及邻道干扰。为保证通信质量需要使用高线性的功率放大器，而高效率的功率放大器通常是非线性的。要解决这个问题，必须采用线性化技术来改善高效率功率放大器的非线性特性。
本文首先从理论上分析了功率放大器的非线性特性，介绍了目前各种线性化技术的原理和优缺点。重点研究了线性化技术中效率高，成本低，且有着广泛应用前景的预失真技术。分析了一种自适应数字预失真方案。从算法原理入手，分析查找表方法的预失真技术。对数字预失真的关键技术提出了设计方法，并采用Matlab软件对其进行仿真。首先仿真了行波管放大器(TWTA)的模型，并在这一模型下验证预失真算法。
仿真结果表明，通过预失真算法可大大降低由TWTA 非线性所引入的带内失真和频谱再生。通过软件仿真，验证了这一设计方案的可行性，取得了预期的效果。最后总结了本课题研究过程中的结论和体会，提出存在的问题和不足之处，并展望今后继续努力的方向。
关键词：射频功率放大器；预失真技术；查找表
ABSTRACT
With the rapid development of wireless communication, RF power amplifier plays the very important role. In order to make more efficient use of frequency spectrum and achieve greater power efficiency，the linear modulation methods and high-efficiency Radio Frequency power amplifiers are widely used. Since the envelope of modulated signal fluctuates，unwanted intermodulation distortions generated when the signal is amplified by the nonlinear RF power amplifiers. The intermodulation distortions will lead to severely inter-symbol interference and adjacent channel interference. The high linear power amplifier has to be used to guarantee communication quality. Unfortunately，power efficient amplifiers are typically nonlinear. For solving this problem，various linearization techniques have been employed to improve the linearity of high efficiency power amplifier.
In this thesis，the non-linear characteristics of power amplifier are analyzed in theory at first. The principle，advantages and disadvantages of various linearization techniques are discussed. To improve the power amplifier efficiency without compromising its linearity, power amplifier linearization is essential. The thesis focus on digital predistortion, which is one of the costs, effective and the most potential technology for RF power amplifier linearization. A novel program of based on LUT adaptive predistortion linearization is proposed in the paper, which is based on the adequate analysis on nonlinear. Design key parts of digital predistortion and simulate the program for travel wave tube amplifier (TWTA) in Matlab software .Simulate the model of power amplifier, and verify the algorithm in this environment.
The results of simulation show the feasibility of the scheme .The simulation results show that the predistortion linearization can reduce in-band distortion and spectrum regrowth greatly introduced by the nonlinear effects of TWTA. At the end of this paper, it concludes the project, points out the existing problems, and gives some suggestions for later work.
Keywords： RF power amplifier； predistortion technique；TUL
