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1、 超宽带论文：基于Chirp函数的超宽带系统干扰抑制设计与研究【中文摘要】自从FCC于2002年批准超宽带(UWB)可以民用以来,超宽带技术引起了人们越来越多的关注。超宽带技术具有传输功率低,低复杂度、低成本,抗干扰能力强及多径分辨率高等优点,被认为是下一代无线个人局域网物理层的标准。超宽带系统的干扰抑制问题一直以来都是研究的热点,本文的主要工作就是利用UWB系统、Chirp函数以及正交互补码的特点,设计基于互补码的Chirp认知超宽带系统,提高系统的抗窄带干扰与多址干扰的能力。本文主要针对直接序列扩频超宽带系统展开理论分析和仿真,关于超宽带技术基本理论的介绍主要包括以下几个方面：首先阐述了超
2、宽带的定义、特点及应用价值,分析了超宽带常用的高斯窄脉冲的时频特性及其各种参数对脉冲时频特性的影响。随后,我们还给出了超宽带系统常用的调制和多址方案,推导了多用户直扩超宽带系统的误码率。最后,论文还简单介绍了超宽带系统室内传播环境的信道特征和IEEE给出的标准超宽带信道模型。UWB信号极宽的带宽决定了其频谱不可避免的和已有的窄带通信系统在频域上重叠,本文通过对Chirp脉冲波形的设计来改变其频域特性,解决超宽带系统和窄带系统共存的问题。论文首先研究了窄带信号的模型和Chirp脉冲的相关基础理论,然后基于反三角函数和反双曲函数,针对超宽带(UWB)系统提出了两种新型的可抑制窄带干扰(NBI)的非
3、线性Chirp波形。最后通过仿真结果验证了采用这两种Chirp脉冲进行传输的超宽带系统在抑制窄带干扰方面的性能有了显著提高。在产生Chirp脉冲之前,需要首先通过频谱感知技术得到窄带系统的频域参数,从而得到自适应Chirp脉冲的时域波形。由于Chirp波形固有的时域和频域的对应关系,这两种脉冲均只需要时域处理即可改变频域特性。除了窄带干扰的影响,多址干扰和多径传输引起的符号间干扰还会导致多用户认知UWB系统容量和频谱效率的下降。本文按序列相关函数特性的不同,分别对互补码、完全互补码及正交互补码给出了定义。随后,详细介绍了串行互补码多址方式扩频和解扩的原理,并在用该方案实现的CDMA系统中仿真验
4、证了正交互补码抗多址和多径干扰的能力。最后,将具有理想自相关和互相关特性的正交互补码应用到超宽带系统中,通过抗窄带干扰的Chirp脉冲携带信息,改善超宽带系统在多址干扰和窄带干扰环境下的误码性能。仿真结果表明,在理想情况下,采用正交互补码的多用户超宽带系统不受多址干扰的影响,使用Chirp脉冲还可以实现系统同时对多址和窄带干扰的抑制。本文在最后一章总结了论文的工作并对未来可继续研究的内容进行了展望。【英文摘要】Ultra-wideband (UWB) has attracted more and more attention in recent years after it was opene
5、d to civilian use by FCC in 2002. The characteristics, such as low power, low cost, interference and multipath immunity, etc, lead UWB technology an excellent candidate for indoor high data rate wireless communications. Historically, NBI mitigation techniques has been a hot research point in UWB tec
6、hnology field, so we mainly focus on the features of UWB system, Chirp function and Orthogonal complementary codes (OCC) in this paper. We design Chirp cognitive radio UWB system based on OCC in this thesis, so as to improve the performance of multi-user UWB system in narrowband environment.Most of
7、the theoretical analysis and simulation results centered on direct sequence spread spectrum UWB system. The basic principles of UWB systems are discussed as follows:firstly, we expatiate on the definition, features and application values of UWB theology. At the same time, the impacts of different pu
8、lse factors on the time frequency character of Gaussian pulses are also analyzed. Then, signal modulation and multi-access methods are carefully studied, and BER of multi-user DS-UWB system is also deduced carefully. Finally, we briefly describe the modeling of ultra-wideband indoor wireless propaga
9、tion channels and standard channel model provided by IEEE.The huge bandwidth of UWB signals forces UWB to coexist with some existed narrowband systems. We go into traditional Chirp waveforms and different NBI models depending on its types. And then, in order to alleviate narrowband interference to U
10、WB systems, design two novel non-linear Chirp functions, arc trigonometric function and arc hyperbolic function, to construct ultra wideband pulses and alleviate narrowband interference (NBI). Simulation results demonstrate that UWB systems composed of the new pulses have significant performance in
11、suppressing the NBI. The adaptive Chirp waveforms generator has to first get the spectra parameters of NBI through spectrum sensing technologies in cognitive radio, so as to get their expression in time domain. Both of them require only time domain processing for the inherent characteristics of thes
12、e Chirp waveforms.Besides the NBIs, multipath interference (MI) and multiple-access interference (MAI) also limits the capacity and the spectrum efficiency of the system. We first define the complementary code, complete complementary code and orthogonal complementary code according to the difference
13、 on the correlation function of the sequence. And then, the specific implementation scheme of spreading and dispreading in serial OCC multi-user system are investigated in detail. In traditional CDMA systems, the excellent multipath and MAI suppression performance of the proposed OCC scheme is confi
14、rmed. At last, we further study the cognitive Chirp UWB system based on orthogonal complementary code and attempt to suppress NBIs and MAI simultaneously. Simulation results are given to verify that under ideal condition, MAI and NBIs will not be a problem if we use an orthogonal complementary code
15、set in the proposed cognitive Chirp UWB system. In the final chapter, the research work in this thesis which has been accomplished is summarized and the future work is prospected.【关键词】超宽带 Chirp波形 窄带干扰 正交互补码【英文关键词】Ultra wideband (UWB) Chirp waveforms (CW) Narrowband interference (NBI) Orthogonal complementary codes (OCC)【目录】基于Chirp函数的超宽带系统干扰抑制设计与研究contents6-8中文摘要8-10Abstract10-11第一章 绪论12-231.1 超宽带概述12-161.1.1 超宽带的定义12-131.1.2 超宽带技术的发展13-151.1.3 超宽带技术的特点和应用15-161.2 本课题研究现状16-191.3 主要研究内容及意义19-211.4 论文结构安排21-23第二章 超宽带基本原理及信道模型23-342.1 UWB理论依据23-242.2 UWB脉冲信号24-262.3 超宽带调制和多址技术26-292.4 UWB无线通信信道模
