摘要
隨著無線通信技術的飛速發展，射頻功率放大器起著越來越重要的作用。出于對更高頻譜利用率和更高功率效率的需求，線性調制技術和高效率的射頻功率放大器得到了廣泛應用。但包絡變化的信號經過非線性射頻功率放大器后會產生互調失真，造成嚴重的碼間干擾及鄰道干擾。為保證通信質量需要使用高線性的功率放大器，而高效率的功率放大器通常是非線性的。要解決這個問題，必須采用線性化技術來改善高效率功率放大器的非線性特性。
本文首先從理論上分析了功率放大器的非線性特性，介紹了目前各種線性化技術的原理和優缺點。重點研究了線性化技術中效率高，成本低，且有著廣泛應用前景的預失真技術。分析了一種自適應數字預失真方案。從算法原理入手，分析查找表方法的預失真技術。對數字預失真的關鍵技術提出了設計方法，并采用Matlab軟件對其進行仿真。首先仿真了行波管放大器(TWTA)的模型，并在這一模型下驗證預失真算法。
仿真結果表明，通過預失真算法可大大降低由TWTA 非線性所引入的帶內失真和頻譜再生。通過軟件仿真，驗證了這一設計方案的可行性，取得了預期的效果。最后總結了本課題研究過程中的結論和體會，提出存在的問題和不足之處，并展望今后繼續努力的方向。
關鍵詞：射頻功率放大器；預失真技術；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
