包络跟踪功率放大器技术研究

发布时间：2018-01-18 11:40

  本文关键词：包络跟踪功率放大器技术研究　出处：《电子科技大学》2015年硕士论文　论文类型：学位论文

  更多相关文章： 包络跟踪 功率放大器 包络调制器 神经网络

【摘要】：包络跟踪是一项用于设计高效率射频功率放大器的技术。这项技术的基本原理是功放漏极或集电极偏置电压随着输出信号功率的变化而实时地进行调整,以维持功放工作于效率较高的区域。尽管原理与概念由来已久并深为人知,包络跟踪技术的工程实践却并非易事。本文就包络跟踪技术中的技术要点进行了理论分析、仿真进实验验证。本文从功率放大器效率公式出发,引出包络跟踪技术的实现形式;将技术难点一一呈现,如包络成形技术、包络调制器实现技术、动态偏置功率放大器设计、数字预失真技术等。包络成形技术根据侧重点不同,可分为最大效率、固定压缩点和固定增益三种。就功放效率指标而言,最大效率成形函数最高而固定增益函数最低;就功放线性指标而言,最大效率成形函数最差而固定增益函数最好。线性度太差会导致数字预失真技术无法对功放非线性进行修正,从而在工程实践中无法运用。包络调制器是包络跟踪技术中最关键的部分,在设计中必须兼顾带宽、效率、噪声、带载能力等。包络调制器的实现方式有直流-直流转换器、线性放大器以及两者合并的混合型放大器。本文中采用多阶噪声成形技术控制多电平直流转换器,成功制作出一款跟踪能力达到300KHz,效率达80%的包络调制器。功率放大器本身即为非线性电路,在漏极偏置电压变化的情况下,放大后的信号线性度将进一步恶化。从最佳阻抗匹配点出发,本文分析了动态偏置对功放设计带来的影响.只有效率而不考虑线性的功率放大器,在现有的通信系统中是没有立足之地的。本文采用神经网络作为功率放大器的建模工具来研究包络跟踪功率放大器的数字预失真线性化技术。实验结果表明,针对8载波GSM信号,互调改善达到26dB以上;针对5MHz带宽的WCDMA信号,ACPR改善达到12dB以上。
[Abstract]:Envelope tracking is a technique used to design high efficiency RF power amplifiers. The basic principle of this technique is that the bias voltage of power amplifier drain or collector is adjusted in real time with the change of output signal power. In order to maintain the power amplifier work in the more efficient areas. Although the principles and concepts have a long history and is well known. The engineering practice of envelope tracking technology is not easy. In this paper, the main points of envelope tracking technology are analyzed theoretically and verified by simulation. The efficiency formula of power amplifier is used in this paper. The realization of envelope tracking technology is introduced. The technical difficulties are presented one by one, such as envelope shaping technology, envelope modulator realization technology, dynamic bias power amplifier design, digital predistortion technology, etc. It can be divided into three types: maximum efficiency, fixed compression point and fixed gain. In terms of power amplifier efficiency index, the maximum efficiency shaping function is the highest and the fixed gain function is the lowest. In terms of the linear index of power amplifier, the maximum efficiency shaping function is the worst and the fixed gain function is the best. The linearity is too poor, so the digital predistortion technology can not correct the nonlinear of power amplifier. The envelope modulator is the most important part of the envelope tracking technology. In the design, the bandwidth, efficiency and noise must be taken into account. The realization of envelope modulator includes DC-DC converter, linear amplifier and hybrid amplifier. In this paper, multilevel DC converter is controlled by multi-order noise shaping technology. An envelope modulator with a tracking capacity of 300kHz and an efficiency of 80% has been successfully fabricated. The power amplifier itself is a nonlinear circuit under the condition of leakage bias voltage change. The linear degree of the amplified signal will deteriorate further. Based on the optimal impedance matching point, this paper analyzes the influence of dynamic bias on the design of the power amplifier. Only the efficiency of the amplifier without consideration of the linear power amplifier. The neural network is used as the modeling tool of the power amplifier to study the digital predistortion linearization technology of the envelope tracking power amplifier. The experimental results show that there is no foothold in the existing communication system. For 8-carrier GSM signal, the improvement of intermodulation is more than 26dB. For WCDMA signal with 5 MHz bandwidth, the improvement of ACPR is more than 12 dB.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN722.75
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本文编号：1440794