OFDM信号的带外功率辐射抑制技术研究与实现

发布时间：2018-04-05 11:44

本文选题：动态频谱接入　切入点：正交频分复用　出处：《电子科技大学》2014年硕士论文

【摘要】：随着信息的爆发式增长,无线通信开始扮演越来越重要的角色,然而属于空中资源的无线频谱却日渐紧张,于是出现了一种基于OFDM技术的动态频谱接入(DSA)方案,这种技术旨在提高对目前已被分配的频谱的利用率。由于OFDM信号存在带外功率过大这一缺点,导致其无法直接与DSA相结合,于是如何降低OFDM信号的带外功率辐射便成为了研究DSA应用的关键之一。本文首先介绍了动态频谱接入技术及其分类,并分析了OFDM技术的基本原理,在此基础之上分析了造成OFDM带外功率过大的两个原因:OFDM时域隐性加窗所造成的旁瓣过大以及信号的峰值功率过高致使功率放大器产生非线性失真的概率增大,针对Rapp功率放大器的非线性失真对信号功率谱密度的影响进行了进一步的分析和仿真。然后,分析和总结了常用的旁瓣和峰均功率比抑制算法,对比了这些方法的优缺点。由于这些方法存在诸多的问题,人们开始研究多选择序列(MCS)和选择性映射(SLM)。这两种技术以其无失真和计算复杂度相对较低等优点得到了广泛关注。在本论文中分析了影响他们性能的各项因素。对基于不同转换矩阵的低复杂度SLM改进方案进行了分析和比较。通过大量的仿真,得到的低相关性转换矩阵方法与传统的SLM相比在扩展因子同样为16的情况下仅有0.1dB左右的性能损失,而计算复杂度却得到了非常显著的降低。最后,对基于改进的转换矩阵的低复杂度SLM建立了定点仿真模型,将定点模型与浮点仿真的性能损失限制在0.3dB以内。在此模型基础上进行电路设计,并介绍了各子模块的接口、核心电路以及Modelsim仿真结果。最后,在Terasic公司DE4开发板之上对所设计电路进行板级测试。经验证,总资源占有率为4%,电路的最高时钟频率能够达到250MHz。
[Abstract]:With the explosion of information, wireless communication begins to play a more and more important role. However, the wireless spectrum which belongs to air resources is becoming increasingly tight, so a dynamic spectrum access scheme based on OFDM technology has emerged.The technology is designed to improve the efficiency of the spectrum currently allocated.Because the outband power of OFDM signal is too large, it can not be directly combined with DSA, so how to reduce the out-of-band power radiation of OFDM signal has become one of the key issues in the study of DSA applications.This paper first introduces the dynamic spectrum access technology and its classification, and analyzes the basic principle of OFDM technology.On the basis of this, the paper analyzes two reasons causing the excessive out-of-band power of OFDM: OFDM, which is caused by the excessive sidelobe caused by the implicit window addition in time domain and the high peak power of the signal, which increases the probability of the nonlinear distortion of the power amplifier.The influence of nonlinear distortion of Rapp power amplifier on signal power spectral density is analyzed and simulated.Then, the common sidelobe and peak-to-average power ratio (PAPR) suppression algorithms are analyzed and summarized, and the advantages and disadvantages of these methods are compared.Due to the many problems in these methods, people begin to study multi-selection sequences (MCSs) and selective mapping (SLM).These two techniques have attracted wide attention due to their advantages of distortion-free and relatively low computational complexity.In this paper, the factors affecting their performance are analyzed.The improvement scheme of low complexity SLM based on different transformation matrix is analyzed and compared.Through a large number of simulations, compared with the traditional SLM, the low correlation transformation matrix method has only about 0.1dB performance loss under the same expansion factor of 16, but the computational complexity is significantly reduced.Finally, a fixed-point simulation model for low-complexity SLM based on improved transformation matrix is established, which limits the performance loss of fixed-point model and floating-point simulation to 0.3dB.On the basis of this model, the circuit is designed, and the interface of each sub-module, the core circuit and the simulation results of Modelsim are introduced.Finally, the designed circuit is tested on the DE4 development board of Terasic Company.It is verified that the total resource share is 4 and the highest clock frequency of the circuit can reach 250 MHz.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN929.53

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