【作者】 张振龙；

【导师】 孙晓颖；

【作者基本信息】 吉林大学 ， 通信与信息系统， 2007， 硕士

【摘要】 超宽带技术具有隐蔽性好、传输速率高、功耗低等诸多优点。但由于其频带很宽,为了使其不干扰其它通信系统,国际上严格限制了它的发射功率,使超宽带信号的传输能力受到了人为的约束。为了进一步改善UWB系统的传输能力,本文从认知无线电的角度对脉冲超宽带(IR-UWB)系统的频谱成形技术进行了深入研究。虽然通过调整超宽带高斯脉冲的脉冲形成因子、导数阶数参数能够改变信号的频谱特性,但不能躲避窄带信号的干扰。由此本文提出通过双脉冲间隔参数及超宽带跳时码时长、脉冲重复时间参数来形成并调整超宽带的频谱缝隙,使之落在窄带信号频率上,进而回避窄带信号频谱的解决办法。为了使频谱缝隙能够随着窄带信号的工作状态作出灵活调整,本文提出了基于循环平稳的窄带信号频率探测方法。本文对UWB脉冲形式及其频谱特性进行了系统分析,推导了超宽带系统波形参数、发射参数与UWB谱缝隙位置、带宽之间的数学关系。仿真结果证明了上述参数对回避窄带信号干扰的有效性。推导了基于循环平稳的窄带信号探测方法,建立了窄带干扰频率与频谱成形参数之间的关系,确立了IR-UWB认知无线电系统频谱成形的完整工作过程,并分析了系统的误码性能。仿真结果表明上述方法能够有效提高IR-UWB系统抗窄带干扰的能力。更多还原

【Abstract】 With short-distance wireless communications using in the military affairs,industry,science,medical treatment and our daily-life, various portable individual communications equipment’s and appliance wiring equipment’s increasing, the source of finity spectrum is more scarcity. Sharing and highest efficiency using spectrum source is a pressing technical problem.UWB whose purpose is sharing the spectrum is a new technology. It have the features of concealment, the high transmission rate, low power consumption and so on. But because of its use of very wide bandwidth, to make it do not interfere with other communications systems, in the international, its emitted power has strictly limited. How to make UWB breakthrough this restrictions and don’t increase interference to other communication system have practical significance to improve the transmission capacity of UWB.The last two years, Cognitive Radio (CR) technology leads the international field of communications extensive attention. It has become an inevitable direction of software radio and considered to be one important way of solute the shortage of spectrum. The basal thinking of CR is it can reliable cognitive spectrum environment in broadband, detect the emergence of primary users, occupy immediately available of the local spectrum and it have not harmful interference to primary users in the whole communication course. The cognitive radio technology brings a new idea for solving the problem which UWB and traditional narrow-band system coexist.IR-UWB can through adjusted Gaussian pulse’s shape factor and the order of the derivative parameters to affect the power spectrum of UWB, but this redressal can’t make UWB spectrum avoiding narrowband signal spectrum. So this paper suggest that through Cognitive Radio wireless signal sensing technology provid frequency parameters of narrow-band signals to adjustment the double-pulse spacing parameters, UWB Time-Hopping repetition time parameter, achieving the real-time adjustment of the spectrum UWB slot and making it always falls on narrow-band signal frequency.Through this paper, it achieves lower emitted power in narrow-band signal frequency and higher emitted power in other spectrum.It breachs FCC spectral mask and improves the transmission capacity of UWB.Main Content of this thesis:Charter 1 summarie the concept of UWB and CR, and analyzes the main problems facing of using UWB in reality and the significance of the research of IR-UWB Cognitive Radio, and explains the purpose of this research study and content.Charter 2 analyzes the effect of UWB Gaussian pulse parameters to power spectral density and the characteristics of TH-PPM UWB power spectral density. Formula and simulation results show the time-hopping interval and pulse repetition frequency affecting its power spectrum of discrete components and the location.Charter 3 introduces the interference relations between UWB signal and narrowband signal and establishs the mathematics relationship of between Narrow-band interference energy intensity and UWB intensity of the power spectral density, and show up double-pulse signal and power spectrum’s expression, and analyzes UWB waveform parameters and the time-hopping parameters affecting UWB shaping of spectrum. Main Content:(1)Derivating the processing gain of matched filter UWB correlation receiver.(2)Derivating time-hopping parameters and double pulse parameters affect UWB signal spectrum, and establishes the mathematical relationship of seamless spectrum position and spectral bandwidth gap between these parameters. (3)Through simulation analysis can find the conclusions which shaping of spectrum makes the power of UWB spectrum on narrow band signal close to zero.Charter 4 starts from the detection methods of cognitive radio signal, and derivates Cycle frequency detection arithmetic, and compares with the traditional energy detecting method. Simulation analyzes the performance of energy exploration and cyclostationary signal detection based on different intensity Gaussian white noise.The basic principle of arithmetic is based on the existing communications signals choice for a stationary circle model, through the hypothesis testing of dual detection, and based on test receiving signal is cycle stationary or not judging the signal.Charter 5 is based on the chapter 2,3,4 , and point out that the interference of Narrowband system to UWB system can pass adjusting UWB signal parameters making UWB signals make the bandwidth of the spectrum slot more than narrowband signal’s. Through these spectrum slot on Narrow-band signal’s working frequency, it can get the purpose of decreasing the interference energy between narrowband signals and UWB signals, improving UWB transmission performance.(1) Based on the relationship of interference frequency and UWB spectrum slot position, and choices appropriate emission parameters making UWB spectrum avoiding narrow-band signal, and concludes the specific adjusted steps of TH-UWB system emission parameters which based on the cognitive condition of interference frequency.(2) Analyzing the performance of the system, and bases on the frequency interference of apperceive, we simulates the Matched filter receiver on the UWB BER which the time-hopping code based on Gauss second derivative function monopulse and double pulse.Charter 6 summarizes the conclusions of this thesis.The innovative work of this thesis:(1) Derivating The mathematics relationship between time-hopping time intervals, Pulse repetition interval parameters, double pulse interval parameters and the spectrum slot position and spectrum slot width of TH-UWB spectrum, solving the parameter problem of IR-UWB Cognitive Radio system spectrum shaping.(2)Derivating cyclostationary narrow-band signal cognitive method, establishing IR-UWB Cognitive Radio system through cyclostationary narrow-band signal detected achieves dynamic process of shaping of spectrum.更多还原