【作者】 王国强；

【导师】 王卿璞；

【作者基本信息】 山东大学 ， 微电子学与固体电子学， 2010， 硕士

【摘要】 随着无线通信技术的飞速发展和人们对高频谱利用率和高功率效率的追求,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。非恒包络调制方式的使用使得射频放大器通常需要采用功率回退的方法来达到系统线性的要求。但是为了提高功率放大器的效率,又要求其工作在饱和状态,这必然就会带来严重的非线性。非线性不仅会导致信号带宽之外的频谱再生或扩展,对邻近信道造成干扰；还会在信号带宽内造成失真,恶化了接收机的比特误码率。为了获得高效率高、线性度好的功率放大器,通常可以采用线性化的方法来实现。数字预失真是所有线性化技术中性价比最好的一种,为了研究数字预失真系统,需要对功率放大器的非线性特性及其记忆效应有非常深入的理解,同时为了进行数字预失真系统的仿真,需要构建准确的功率放大器行为模型。本文主要是对宽带功率放大器的非线性特性、记忆效应、行为模型以及数字预失真系统进行研究。功率放大器非线性特性部分主要阐述了非线性特性的描述、非线性特征参数、非线性产生的失真产物、非线性分析方法等；功率放大器记忆效应部分主要分析了记忆效应的识别、产生的原因,给出了记忆效应消除的方法；功率放大器的行为模型部分主要对当前提出的典型行为模型进行的分析和比较；数字预失真系统与仿真实现部分主要分析了当前主要的线性化技术并进行了比较,在MATLAB环境下对数字预失真系统进行了系统构建与仿真；搭建数字预失真系统实验平台,并进行实验验证。本论文在大量阅读文献的基础上针对预失真技术进行了研究。主要内容有：1.分析了功率放大器的非线性特性以及其衡量指标；并通过单双音信号阐述了非线性失真在时域、频域中的影响,即随着输入功率的增加,无论是谐波,还是互调产物都逐渐增大,时域上曲线发生变形(幅度不再线性变化,相位发生旋转),频域上带外出现谐波,带内互调分量增大,使得频谱发生扩散；并分析了功率放大器记忆效应的存在,及其对预失真设计方案带来的影响。2.阐述了预失真技术的基本原理,分别使用查找表、多项式和人工神经网络等技术对功率放大器模型进行辨识仿真和预失真设计仿真,并对三种方法综合比较后,自主设计出最符合我们实验条件和实际情况的改进记忆多项式技术。并利用我们的记忆多项式线性化技术对射频功率放大器进行辨识,设计数字预失真系统。3.使用ADS和MATLAB软件联合仿真的形式来评估整个预失真系统的线性化效果。用ADS仿真一定条件的功率放大器,使用我们自主设计的预失真技术对该放大器进行非线性预补偿,完成该技术验证第一步。4.预失真技术实验,实现预失真系统实际电路,对实际功率放大器进行非线性预补偿,进而完成功放的线性化。经上述3中ADS仿真验证后,仍然无法完全确定我们设计方案的正确性,因此必须进行实际验证。我们分别通过对WANTCOM功率放大器和成都新光的功率放大器进行线性化,不仅可以验证方案的可行性,还可以促进方案的改善。5、得出实验结论,并对今后学习工作规划。更多还原

【Abstract】 With the rapid development of wireless communication,in order to make more efficient use of frequency spectrum and achieve greater power efficiency,the linear modulation methods and high-efficiency Radia Frequency power amplifiers are widely used.The RF amplifiers usually use power back-off to achieve the system’s linearity requirement under non-constant envelope modulation.However,in order to improve output power and efficiency,power amplifiers always work in the saturated state,which will produce severe nonlinear distortion. The nonlinearity creates spectral growth (broadening) beyond the signal bandwidth, which interferes with adjacent channels. It also causes distortions within the signal bandwidth, which decreases the bit error rate at the receiver.In order to achieve high linear and reasonably efficient Power amplifier, we can use linearization techniques in general. Digital predistortion is one of the most effective ways among all linearization techniques. So the main goal of our research is that implements digital predistortion system. In order to study digital predistortion system and simulate it, we need to master and understand nonlinear characteristics and memory effects of power amplifier, and mean while, to build exact behavioral model of power amplifier. This thesis discusses and studies the following contents step by step, including PA nonlinear characteristic and distortion, PA memory effect and cancellation, PA behavioral model and digital predistortion system and simulating realization.In the section of PA nonlinear characteristic, introduces representation of nonlinear characteristic, nonlinear characteristic parameters, distortion products, nonlinear analytical methods, characteristic simulation, and so on. In the section of PA memory effects, analyzes identification of memory effects, reason causing memory effects, verifies existence of memory effects, and gives some methods canceling memory effects. In the section of PA behavioral model, analyzes and compares a few typical PA behavioral model proposed. In the section of digital predistortion system and simulating implementation, analyzes and compares a few main linearization techniques, builds and simulates digital-base band predistortion system in MATLAB circumstance, builds the system of experiments and verifies the system.The main tasks and contributions in this thesis can be summarized as follows:1. Analyzes PA nonlinear characteristics and resulting distortion, concludes that amplitude of inter modulation products will increase and output spectrum will be deteriorate when input power increases. Verifies existence of memory effects through theoretical analysis. The principles of predistorter are described. The look-up-table based predistorters are discussed in detail.2. The principles of predistortion techniques are described. A predistortion method using the ameliorative Memory-Polynomials is proposed to linearize power amplifiers.3. Uses the joint simulation of ADS and MATLAB software to evaluate the performance of this system.4. Builds the experiments system of Digital Predistortion, verifies the system of DPD to prove the advantage of the system.5. Giving the results of the experiments system of Digital Predistortion. Plan the work of future.更多还原