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摘要正交频分复用（OFDM，Orthogonal Frequency Division Multiplexing）技术可以出色地对抗抗多径衰落、消除码间干扰，并且具有极高的频谱利用率。此外它还采用了快速傅立叶变换，大大降低了收发机的实现复杂度，因此被广泛地应用于HDSL、ADSL、DAB、HDTV、WLAN等领域中。 66211
但是，目前OFDM技术还有很多关键问题没有得到有效解决，如对频偏敏感、高峰均功率比问题等，这些都限制了OFDM技术的近一步广泛应用。本论文主要围绕自适应压扩法降低峰均功率比问题展开论述，并利用matlab软件完成了仿真。主要做了以下工作：
论文首先回顾OFDM发展历程，说明了该技术的优缺点，讲解了OFDM技术原理，介绍了OFDM信号的产生过程，并对OFDM信号的收发机制进行了仿真。接着，给出峰均功率比的定义和分布，分析了产生高峰均值的原因，简要地介绍了其它预畸变方法，如限幅法、峰值加窗、传统的压扩技术。最后，分析自适应压扩法降低PAPR的性能，并用matlab完成相关仿真。
毕业论文关键词 正交频分复用，峰均功率比，自适应动态压扩法
毕业设计说明书（论文）外文摘要
Title The Study of Companding-based PAPR Reduction in OFDM System
Abstract
OFDM (Orthogonal Frequency Division Multiplexing) can strongly combat multi-path fading and dispersive channel interference. It also has high bandwidth efficiency. Besides, using DFT can greatly reduce the complexity of the receivers and transmitters so OFDM has been widely used in several areas such as HDSL, ADSL, DAB, HDTV and WLAN.
However, many key problems of OFDM system have not been solved yet, such as sensitivity of frequency offsets and high PAPR (Peak to Average Power Ratio), which limit wide application of OFDM technique. This dissertation mainly focuses on the technique of adaptive dynamic range companding to reduce the high value of PAPR, and uses MATLAB software to achieve simulation. The following work has been done:
Firstly, the history of OFDM technique, its key techniques, advantages and disadvantages of OFDM technology are analyzed.
Secondly, the principle of OFDM technology and the production of OFDM signal are introduced, then MATLAB is used to simulate the production and reception of OFDM signal.
Thirdly, the definition and distribution of PAPR are introduced. The reason of high PAPR is deduced. Some pre-distortion techniques like clipping and filtering, peak windowing and traditional companding technique are analyzed briefly. Analyze the performance of Adaptive Dynamic Range Companding of reducing PAPR, then use matlab to achieve relative simulation.
Keywords orthogonal frequency pision multiplexing,
peak-to-average power ratio, adaptive dynamic range companding
目 次
1 绪论 1
1．1 研究目的与意义 2
1．3 论文的章节安排 3
2 OFDM技术的基本原理与关键技术 5
2．1 FDM与OFDM的比较 5
2．2 OFDM系统的基本原理 6
2．3 离散傅立叶变换(DFT)的应用 8
2．4傅立叶变换的过采样 10
2．5 保护间隔和循环前缀 12
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