【作者】 南敬昌；

【导师】 刘元安；

【作者基本信息】 北京邮电大学 ， 电磁场与微波技术， 2007， 博士

【摘要】 功率放大器是通信系统中最重要的器件，存在固有的非线性。非线性导致了信号带宽之外的频谱再生或扩展，对邻近信道造成干扰。同时，这种非线性在信号带宽内也造成失真，恶化了接收机的比特误码率。新型传输格式，比如宽带码分多址(WCDMA)和正交频分复用(OFDM)，由于具有较高的峰均功率比(PAPR)尤其容易受到非线性失真的影响，造成功率放大器记忆效应的产生，使功率放大器的特性发生变化，互调产物发生不平衡，同样引起失真。如果我们为了获得功率放大器所需的线性度，仅仅采用简单地回退方法，那么功率放大器的效率在高峰均功率比情况下将会是非常小。为了获得高效率同时线性度比较好的功率放大器，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。因此我们主要研究目标是数字预失真系统的实现，包括真实预失真系统和模拟预失真系统的实现。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。本文就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逐步展开研究的。本文对功率放大器的非线性特性及其引起的失真、记忆效应的产生及其消除、行为模型的构建以及数字预失真系统仿真实现进行了全面的描述与研究。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、非线性分析方法和非线性特性仿真实现等；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，用仿真的方法证实了记忆效应的存在，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，给出了单位延迟和稀疏延迟记忆多项式行为模型的算法并对模型性能进行了分析，推导了基于正交函数-Laguerre函数的Volterra级数行为模型算法并验证该模型的性能；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，对数字射频预失真系统和数字基带预失真系统在ADS环境下进行了系统构建并仿真。本文对功率放大器的研究是基于电路与系统级仿真软件ADS和MATLAB数学工具软件进行研究的。本文所使用的放大器来自于freescale半导体的MRF21030晶体管所设计的测试版功率放大器。本文的主要工作和贡献在于：1．用实例仿真的方法分析了功率放大器的非线性特性以及产生失真的情况，即随着输入功率的增加，互调产物失真增大，频谱恶化；2．用理论和仿真的方法分析了功率放大器记忆效应的存在，提出了一种减小热记忆效应的思想-预失真器温度补偿法，并进行了仿真，证明了其有效性；3．在对各种行为模型比较的基础上，提出了一种稀疏延迟抽头记忆多项式行为模型和基于正交函数Laguerre的Volterra级数扩展行为模型，用MATLAB验证了这两种模型的性能优势；4．对数字预失真系统在ADS环境下进行了构建并对预失真系统的性能进行了仿真，验证了构建的预失真系统能够达到预失真效果。构建了具有记忆效应的功率放大器模型并进行了仿真，验证了构建的系统具有自适应性。构建的系统可以通过改变输入信号、功率放大器模型以及系统的参数来得到不同系统、不同参数的预失真系统。这对实际预失真系统的设计与实现具有重要的参考价值。以上的一些研究成果，以学术论文的形式发表于国内外一些重要期刊和会议上。更多还原

【Abstract】 Power amplifiers are essential components in communication systems and are inherently nonlinear. The nonlinearity creates spectral growth (broadening) beyond the signal bandwidth, which interferes with adjacent channels. It also causes distortions within the signal bandwitdth, which decreases the bit error rate at the receiver. Newer transmissionformats, such as wideband code division multiple access (WCDMA) ororthogonal frequency division multiplexing (OFDM), are especially vulnerable to the nonlinear distortions due to their high peak-to-average power ratios (PAPRs). This kind of input signal causes memory effects of power amplifier, which are with phenomenon of PA nonlinear characteristic variation and asymmetries in lower and upper sidebands of inter-modulation products, which will also result in distortion. If we simply back-off the input signal to achieve the linearity required for the power amplifier, the power amplifier efficiency will be very low for high PAPR signals.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, main goal of our research is that implements digital predistortion system, including actual system and simulation 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 meanwhile, 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, proposes a memory polynomial model algorithm with sparse delay taps and compare it with memory polynomial model with unit delay taps, derives algorithm of Volterra model based on Laguerre orthonomal function and verifies performance of this model. In the section of digital predistortion system and simulating implementation, analyzes and compares a few main linearization techniques, builds and simulates digital/RF predistortion and digital-baseband predistortion system in ADS circumstance.The study of PA is based on ADS and MATLAB software. The PA used in the thesis comes from freescale semiconductor Inc.The main tasks and contributions in this thesis can be summarized as follows1. Analyzes PA nonlinear characteristics and resulting distortion with ADS software, concludes that amplitude of intermodulation products will increase and output spectrum will be deteriorate when input power increases.2. Verifies existence of memory effects through theoretical analysis and simulation, proposes an idea reducing thermal memory effects, that is, temperature compensation method of predistorter, and simulate the idea and validate its validity.3. On basis of comparison of some PA behavioral models, proposes a kind of memory polynomial behavioral model with sparse delay taps and a kind of Volterra-series expansion model based on Laguerre orthonomal function, and verifies accuracy of these two kinds of models.4. Builds digital predistortion system in ADS circumstance and simulate results show its validity. Creates PA behavioral model with memory effects and simulate predistortion system with it, verifies adaptation of built digital predistortion system.According to above tasks and achievements, some technical papers have been published in relative conference and periodical.更多还原