摘要
在欧洲第三代移动通信(3G)已经融入人们的生活,在中国3G也已指日可待。第三代移动通信系统要支持大量各种类型的业务,可在任何地方、任何时间向任何人提供个人通信业务,就需要良好的网络结构支持。干线放大器、直放站在网络优化中起着相当重要的作用。功率放大器作为干线放大器和直放站中的关键部件,其性能对系统有较大影响。现代通信系统的信息传输技术正朝着多载波、多电平、宽频带和高峰均比方向飞速发展,新的宽带数字传输技术(如OFDM、WCDMA等)和高频谱效率的调制方式(如QPSK等)正获得越来越广泛的应用。但这些基于非恒定包络的高效的多载波/多信道数字调制传输技术对于射频功率放大器的线性度具有很高的要求,经过非线性射频功率放大器放大后会产生众多的互调失真分量,从而导致功率放大器输出信号频谱的扩展,形成对邻近信道的干扰。现代无线通信系统对于邻道干扰都有严格的限制,这就为功率放大器设计带来了挑战。
本设计主要是针对WCDMA通信系统中干线放大器、直放站的应用设计出20W高线性功率放大器。论文首先介绍了在应用于WCDMA下行链路信号放大情况下影响功率放大器的线性度的指标参数以及线性指标的测量参数。详细分析了射频功率放大器的非线性特性,简单介绍了回退、前馈、预失真等各种线性化技术的基本原理。论文在参考国内外文献的基础上对记忆效应也作了相应的总结。透过这些分析总结最终选择模拟预失真作为本设计的线性化手段。通过严格的预失真模块方案论证、预失真器的器件选择和精心调试,设计实现了工作频率范围在2110MHz～2170MHz放大器的预失真模块部分、驱动级、主功放,最终实现了结构简单、成本较低的模拟预失真系统,完成了对放大器的线性化。
The third generation mobile communication (3G) has already integrated with people's life in European, which is also just been around the corner in China. The third generation mobile communication system which could support massive different kinds of services, and provide person-to-person communication service to anybody, in any place, any time needs good network architecture support. The trunk amplifier and the repeater are very important in optimizing the network. As the key part of the trunk amplifier and repeater, power amplifier plays an important role in these systems. Its performance has greatly affects on the system. The information transmission technology of modern communication system is developing rapidly in the direction of multi-carrier,multi-level,broad band and high Peak-Average- Ratio(PAR).New broad band digital transmission techniques(such as OFDM, WCDMA)and high spectrum efficiency modulation techniques (such as QPSK)are extensive used. These high efficient multi-carrier & multi-channel digital modulation transmission techniques, which are based on non-constant envelope,request high linearity of radio frequency power amplifiers(RF RAs).When signal is amplified by RF PAs,intermodulation distortion is generated,which results in spectral regrowth,then leads to adjacent channel interference. In modern wireless communication system,adjacent channel interference has got stringent restrictions, so it is challenge to designing PA used in modern communication systems.
The main job of this project is developing a 20W high linear power amplifier which could be used in the trunk amplifier and repeater that working on WCDMA communication system. In this paper, we first introduced the parameters which may affect the Linearity of power amplifier when used in the enlargement of WCDMA downlink signal as well as the linearity parameter. The response of nonlinear radio frequency power amplifier also discussed as well as the principle of Linearization technology such as back off, feedback, predistortion and so on. The summary to the memory effect is made in this paper with referring to the domestic and foreign literature. With the help of these analyses and summarize, finally we choose the analog predistortion as the Linearization method of this design. Through the strict predistortion module project concept demonstration, the predistortion component choice and the careful debugging, we finished the design of the predistorter, the driver and the main power amplifier which working on 2110MHz-2170MHz.The predistortion system also finished finally with simply structure, low cost which the linearity of power amplifying is improved.
引文
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