【作者】 王俊；

【导师】 王东进；

【作者基本信息】 中国科学技术大学 ， 电磁场与微波技术， 2007， 博士

【摘要】 超宽带电磁脉冲是正在蓬勃发展中的前沿性研究领域，它具有瞬态和超宽带的特点，有广阔的应用前景，除军事领域外，已在目标成像、地下探测、医疗等民用领域开始应用。由于它在产生、辐射、传播、接收以及处理等方面与常规的电磁信号有很大区别，因此将极大地促进这些领域的技术进步，推动新型的雷达和通信系统研制。自2002年美国联邦通信委员会(Federal Communication Committee，FCC)开放超宽带标准以来，采用基带脉冲的超宽带技术因为其系统结构简单、易于集成，并且具有定位和探测等潜在能力，得到了学术界的广泛关注。本论文以超宽带无线通信为背景研究瞬态电磁脉冲的产生、控制和检测技术。论文工作围绕着窄脉冲信号的瞬态和超宽带特性而展开，从脉冲信号的描述入手，或采用时频域分析的方法，或采用傅立叶级数分析的方法，归纳出窄脉冲信号的根本特征。目的是为窄脉冲的波形设计和信号产生方法提供理论依据和指导思想，为低成本低复杂度的脉冲检测方法提供新的思路。在此基础上，研究脉冲信号产生、调制和检测的工程实现技术，为IR-UWB迈向实际应用提供可靠的解决方案。主要的研究内容和创新成果如下：针对脉冲信号瞬态和低占空比的特点，采用时频分析的方法来分析，归结出脉冲信号的根本特征：在时域上的瞬态和低占空比；在频域上带内频谱相位线性，频谱包络平滑。注意到信号在时域上的持续时间和在频域上的频谱包络、频谱相位之间的对应关系，提出一种在一定频谱规范限制下，综合优化信号持续时间和频谱利用率的升余弦滚降的脉冲信号波形设计方法，该方法不仅可以设计满足FCC的脉冲波形，也可以方便的实现对干扰频带的频谱限制。寻找合适的脉冲产生结构是提高脉冲系统性能的重要方法之一，从时域特征出发，分析了一种基于阶跃二极管的直接脉冲产生结构；从频域特征出发，分析一种基于隧道二极管的带载波脉冲发生结构；理论分析和实验结果表明，这两种电路结构适合用于IR-UWB系统微功率窄脉冲信号产生。在信号接收上，IR-UWB面临的主要问题是简单有效的窄脉冲信号接收和快速的精确同步技术。由于窄脉冲信号能量集中，在出现的瞬间具有极高的信噪比，提出了一种峰值检测的IR-UWB非相干接收方法，采用脉冲幅度实现对信号检测，借鉴脉冲雷达信号检测的思想，通过脉冲延展克服的系统对定时精度要求高的难度。为了进一步解决在多径环境中的脉冲帧间干扰问题，注意到采用恒虚警接收时信号占空比随着信噪比增加呈单调增加的特点，采用基于接收信号占空比统计的自动增益控制方法，保证判决门限在合适的电平上。考虑到脉冲的低占空比特点，提出采用多相时钟取样的同步方法，降低单路的取样速率。同时，为了充分利用多径信号能量，采用了N／M联合检测方法，降低了同步在非最大径时的漏警概率。综合上面的信号检测方法、AGC方法以及同步方法，为IR-UWB无线系统的低成本、小型化、低功耗接收提供了一个完整的解决方案。文中还给出了综合这些方法时在室内多径信号下接收性能的仿真结果，仿真表明这种方法在室内环境下可以可靠工作在数兆到数十兆的传输速率上。本文最后采用理论分析和实验验证相结合的方法研究了IR-UWB无线系统的工程技术。研究了几种IR-UWB射频前端收发信机关键电路的设计和实现技术，使之适合于实际的IR-UWB无线系统。给出了一个基于峰值检测接收的IR-UWB无线传输系统的设计，首次在实验室实现了高达190Mbps的无线脉冲超宽带收发演示系统。在该系统上成功的演示了多路HDTV图像和文件的混合传输，性能稳定。更多还原

【Abstract】 The Ultra-Wideband (UWB) electromagnetic pulse is one of the most important and vigorously developing research field, it is characteristic of the transient and the ultra-wideband, and has the wide prospects for application. It has attracted increasing attention owing to civil application in target identification, medicine and object detection under ground etc. It will extremely promote technological progress of these field, and it is able to develop the new type of UWB radar and communication system due to its different from normal electromagnetic signal in generating, radiation, propagating, receiving and processing etc. UWB technology has become a strong candidate for wireless personal communications (WPAN) since the Federal Communications Commission (FCC) has released the commercial use of UWB systems in 2002. Impulse Radio Ultra-wideband (IR-UWB) scheme has received more and more attention due to its low complexity, numerous subsidiary functions (such as orientation and detection) and application prospects.this paper presents thorough investigation in transient electromagnetic wave generation, its control and detection in wireless communication. By describing the narrow pulse in time-frequency analysis and Fourier analysis, we show the intrinsic properties of transient and ultra-wideband short pulses. This work set the theoretic foundation and insight in pulse shaping design and signal generation. It also offers inspiration in low cost and simple pulse detection. Further more, reliable solution can be retrieved for generating, modulating and detection signal in industrial application, propelling IR-UWB practical application.A time-frequency analysis method for short pulse is proposed. The difference and symmetry between IR-UWB signal, narrowband sinusoidal signal and other UWB realization signal is defined by this method. The key features of IR-UWB signal are the transient and low duty cycle in time domain, flat envelope and linear phase in frequency domain.A RF modulation UWB transceiver structure is proposed to generate and modulate the short pulses. pulse signal of high repetition and stability is achieved by single triggered pulse generator, with the data modulated after pulse generation. Based on time-frequency analysis, a novel method to design the waveforms of IR-UWB signals is proposed. The constructed waveforms are with raised cosine roll-off frequency spectrum and less time duration. Furthermore, series of time-domain waveforms with orthogonal properties constructed by this method can be adopted in high-level modulated UWB systems. Two kinds of pulse generation methods are proposed based on the analysis of Impulse signal. One is direct pulse generator based on step recovery diode and the other is carrier pulse generator based on tunnel diode.A receiving method adopting pulse’s peak detection for IR-UWB system is proposed, which can reduce the requirement of high timing precision. To overcome the frame interference, an AGC method based on receiving duty cycle has been used. taking the pulse’s characteristic of low duty cycle into account, we use multi-phase sampling clock synchronization method, to reduce the single-route sampling rate. Adopting peak detection, AGC based on receiving duty cycle and multi-phase synchronization, the method can be an optional scheme for lowering sampling rate and system realization cost.engineering methods of IR-UWB wireless systems which focus on the RF front-end of the transceiver are studied by theoretical analysis and experimental verification. Pulse generation and pulse modulation circuits based on step-recovery diode, high-speed digital logic element circuit, RF switches and high-speed mixer are proposed. Aiming at the relevant reception and peak detection of non-associated receiving, a new type of short-term gated integrator circuit and transient pulse detection circuit are proposed for short pulse reception. Finally, a design of IR-UWB wireless transmission system based on pulse peak detection is shown. High rate of 190Mbps is achieved for the first time in laboratory. The system has been verified by transmission of real-time no compression video and HDTV using USB2.0 over UWB.更多还原