超宽带搜救雷达发射信号及径向分辨率研究

研究给出了城市灾害救助与生命搜索用超宽带搜救雷达的发射信号模型、目标信息模型、回波模型，在此基础上对雷达径向分辨率与发射信号脉冲宽度、脉冲间隔、脉冲串长度的关系进行了分析探讨。并对模型在Matlab上做了仿真。得出结论，随着雷达脉冲信号宽度增加，信号的UWB特性逐渐消失，目标对信号的多散射中心个数逐渐减少，直至成为点散射，雷达径向分辨能力逐渐变差，雷达一维时间图像逐渐变得模糊。     

超宽带线性调频雷达目标回波模型

超宽带雷达具有高分辨能力,它探测到复杂目标时,目标总的电磁散射是多散射中心的合成,回波信号不同于普通的窄带雷达回波。文中分析了在超宽带信号照射下的目标散射特性,得到超宽带雷达的一般模型。     

Ultrawideband radars: Features and capabilities

Features of ultrawideband (UWB) radars, which radiate signals whose spatial duration is substantially smaller than the antenna dimensions and/or the longitudinal dimension of the illuminated target, are analyzed. It is shown that, during the radar observation of the target, this signal changes its shape several times and enters the radar receiver as an unknown signal. In many cases, this circumstance prohibits application of the traditional theory for the design of UWB radars. Methods for calculating the characteristics of UWB radars on the basis of the energy approach are proposed. Examples of engineering and circuit designs of several UWB radars are presented. Possible lines of development of the technology and technique of such radars are considered.     

超宽带条件下运动目标的高分辨分析方法

该文首先分析了在超宽带条件下静态雷达目标的频域响应特性,提出了一种更符合目标散射实际情况的高分辨分析参数化方法,该方法通过对目标回波进行ARMA模型状态空间近似,提取目标的散射极点来获得散射点的散射类型和距离信息。在目标存在运动时,目标的回波模型是由静态回波模型与一个含运动参数的多项式相位因子组成。据此,该文提出采用循环统计量的方法来进行速度估计,经过速度补偿消除运动影响后可获得超宽带条件下目标的散射极点的精确估计。仿真实验结果表明该方法对静止和运动目标都能够获得目标精确的一维距离信息和各散射点的散射机理类型,对于获取超宽带条件下目标高分辨分析是十分有效的。     

Ultrawide band radar signal detection, estimation and experiment

With reference to the air target detection of ultra-wide band (UWB)/impulse radar(IR), the transient signal processing techniques was discussed. In weak UWB signal detection, the wavelet transforms and high order spectrum estimation techniques were preferred. In target characteristic analysis, a time domain bispectrum estimation algorithm was used to analyze the target impulse response, which could estimate accurately local scattering distribution of complex target. A free field IR experimental system installed in an anechoic chamber was used. With this system, experiments to several target models were made. The results of these experiments verified the signal processing method efficiency.     

UWB Echo Signal Detection With Ultra-Low Rate Sampling Based on Compressed Sensing

A major challenge in ultra-wide-band (UWB) signal processing is the requirement for very high sampling rate. The recently emerging compressed sensing (CS) theory makes processing UWB signal at a low sampling rate possible if the signal has a sparse representation in a certain space. Based on the CS theory, a system for sampling UWB echo signal at a rate much lower than Nyquist rate and performing signal detection is proposed in this paper. First, an approach of constructing basis functions according to matching rules is proposed to achieve sparse signal representation because the sparse representation of signal is the most important precondition for the use of CS theory. Second, based on the matching basis functions and using analog-to-information converter, a UWB signal detection system is designed in the framework of the CS theory. With this system, a UWB signal, such as a linear frequency-modulated signal in radar system, can be sampled at about 10% of Nyquist rate, but still can be reconstructed and detected with overwhelming probability. The simulation results show that the proposed method is effective for sampling and detecting UWB signal directly even without a very high-frequency analog-to-digital converter.     

超宽带雷达信号处理技术和实验研究

针对探测空中目标的超宽带(UWB)/冲激雷达,本文讨论了UWB/冲激雷达的信号处理技术,主要是信号检测和目标特性分析,首先讨论了目标检测技术,提出了用小波变换和高阶谱估计技术在变换域内进行检测的算法;其次讨论了目标特性分析技术,采用了高阶谱估计,提出了一种时域双谱估计算法,它可精确估计复杂形体目标的局部散射中心的分布.最后,结合作者等人研制的冲激雷达实验系统,对上述信号处理方法进行了实验研究,验证了上述信号处理方法的有效性。     

NMTI方法在UWB LFM雷达系统中的应用

介绍了超宽带雷达的定义及其基本特点，讨论了非相干动目标显示方法的原理和实现方案，分析了该方法适用于超宽带雷达系统的原因，介绍了几种杂波类型及其相应的特点。文中建立了超宽带线性调频信号回波模型，并进行了NMTI方法的仿真分析。给出了在不同输入信杂比、目标速度、信号带宽、杂波分布、雷达脉冲重复频率等条件下的仿真结果，验证了非相干动目标显示方法消除杂波的有效性。     

超宽谱雷达人体目标识别的新方法

现有的超宽谱探人雷达的人体目标识别准确率不高,或者不进行识别而直接显示信号处理结果。文中提出了一种可以应用于超宽谱探人雷达的人体识别新方法,采用信号幅值和离散系数相结合的方式对探测区域内的人体目标有无进行识别,并进行了大量的探测实验,给出了结果。所采信号的识别结果表明该方法适用于超宽谱探人雷达的人体目标识别。     

状态空间法在超宽带雷达动目标速度及距离像估计中的应用

该文通过状态空间(State-Space, SS)法高分辨估计超宽带(Ultra-Wide Band, UWB)雷达运动目标径向速度及其距离像。首先,结合具有伸缩的UWB雷达回波模型获得散射体频域冲激响应,以构建SS所需的Hankel矩阵。其次,利用SS估计UWB雷达高速运动目标径向速度及距离像。进一步,分别推导了上述估计参数的克拉美-罗下界(Cramr-Rao Lower Bound, CRLB)。SS法不但能获得目标高分辨距离像,而且较好地规避了多普勒随信号带宽内频率变化,即多普勒色散对径向速度估计的影响。该方法亦具有良好的噪声抑制能力。此外,其只需目标频域冲激响应,并未涉及具体发射波形,因此未受发射信号形式的限制,这不同于利用小波变换估计相关参数的方法。仿真实验验证了该方法的可行及有效性。     

基于正向建模的目标超宽带电磁脉冲雷达回波仿真

为了快速获取超宽带（ultra-wideband,UWB）电磁脉冲激励下雷达目标的时域电磁响应,提出了一种基于散射中心正向建模的目标时域回波仿真方法.从目标几何模型出发,利用空间射线分集技术对强散射源进行分离,通过模型参数正向确定方法构建出目标的属性散射中心模型,用以表征目标高频电磁散射特性,并在UWB电磁脉冲激励下进行仿真运算,获得目标时域回波信号.以典型目标SLICY为例,基于正向建模的散射中心模型,快速获取不同UWB电磁脉冲激励下的雷达回波信号,与高频仿真方法得到的一维距离像（high resolution radar profile,HRRP）进行对比分析,吻合良好.由此验证了本文提出的回波仿真方法的有效性,为不同辐射源激励下目标的快速电磁响应研究提供了一种新思路.     

基于无载频脉冲雷达信号等幅度追踪法检测生命信号

该文首先详细分析了无载频脉冲雷达检测生命信号的基本原理,然后提出了基于回波信号等幅度追踪法检测生命信号的方法。采用自主研发的雷达系统进行检测,结果表明该文提出的检测方法有效。该方法不但能准确判定生命体的有无,而且能够同时提供呼吸信号幅度、频率特征及生命体的位置信息,在短距离非接触式生命信号检测中较传统等距离法有明显优势。     

基于和差波束极化特性的目标极化散射矩阵测量方法研究

该文建立了一种基于常规单脉冲体制的目标全极化散射矩阵测量算法。首先证明了该型雷达天线具有复杂的极化结构,并且对回波信号的极化特性有一定的敏感性。利用单脉冲雷达和差通道的极化特性在获取目标角度信息的同时利用一个脉冲重复周期即可完成目标极化散射矩阵的测量,降低了全极化单脉冲雷达研发的系统复杂度和设计成本,通过电磁计算和仿真分析验证了上述研究的正确性。这对于开发现有雷达装备的极化测量处理能力、提升其抗干扰和目标识别能力具有一定的启发和指导意义。     

基于快速后向投影的超宽带冰雷达数据成像算法

该文提出一种新的冰雷达成像算法,该算法可以在获得高分辨率冰下剖面图的同时,拥有较高的处理效率.该算法是一种基于快速后向投影的超宽带(UWB)冰雷达成像方法,其修正了多层媒质情况下的雷达与目标之间的距离,以及因多层媒质造成的距离徙动几何变化.该文分析了算法的原理,给出了算法实现的具体步骤,并将其应用于点目标仿真和航空冰雷...     

A channelized digital receiver design for UWB systems in a multi-path indoor environment

Due to the very wide bandwidth of UWB system, it is hard if not impossible to design high speed and high resolution ADCs with today’s technology. This problem can be solved if the received UWB signal is split into a number of subbands by power splitters, analog low-pass filters, mixers and digital filters. By doing this, each of subbands can be sampled at a fraction of effective sampling frequency. In this paper, we present a simpler channelized receiver architecture for UWB systems than previously published work. Moreover, we present a new, though more complex, channelized receiver design for UWB systems in a multipath propagation environment. We also show through simulation that this new receiver achieves very good BER performance.     

基于PCA和DCT的雷达人体动作识别

无载波超宽带雷达人体动作识别系统的关键优势在于无载波超宽带雷达具有极高的分辨率,能够捕获人体的细微动作变化,并且对于室内复杂环境具有很强的抗干扰能力。但是由于无载波超宽带雷达信号不含载波信息,本身能量集中于极窄的波形内,并且发射信号与回波相关性弱,因此传统的提取信号特征的方法不再适用。针对这一问题,首次搭建无载波超宽带雷达人体动作识别系统,并提出一种新颖的基于主成分分析法（PCA）和离散余弦变换（DCT）相结合的无载波超宽带雷达人体动作识别方法,同时利用改进的网格搜索算法优化支持向量机的参数并验证该方法的优越性。最后,基于实测数据在Matlab平台上进行仿真,对实测的10种不同类型的人体动作进行分类识别,实验结果显示,该方法具有很高的识别率,针对不同的方案识别率均能达到99%以上,对小训练样本具有很强的鲁棒性。     

多斜率步进调频连续波信号在汽车防撞雷达中的应用

该文首先介绍了工作在毫米波段的汽车防撞雷达的有关情况,然后针对其在实际工作情况下遇到的虚警问题,提出了一种新的雷达发射信号波形,即多斜率步进调频连续波信号。该波形可以容易地数字化产生,同时其相应的信号处理降低了传统的高分辨率雷达对高速宽带信号处理的要求。该文还提出了一种用于多个车辆目标检测的逐次逼近算法,仿真结果表明,该算法能够有效地去除虚假目标。     

Frequency Subband Processing and Feature Analysis of Forward-Looking Ground-Penetrating Radar Signals for Land-Mine Detection

There has been significant amount of study on the use of ground-penetrating radar (GPR) for land-mine detection. This paper presents our analysis of GPR data collected at a U.S. Army test site using a new approach based on frequency subband processing. In this approach, from the radar data that have over 2.5 GHz of bandwidth, we compute separate radar images using the one wide (2 GHz) and four narrow (0.6 GHz) frequency subbands. The results indicate that signals for different frequency subbands are significantly different and give very different performance in land-mine detection. In addition, we also examine a number of features extracted from the GPR data, including magnitude and local-contrast features, ratio between copolarization and cross-polarization signals, and features obtained using polarimetric decomposition. Feature selection procedures are employed to find subsets of features that improve detection performance when combined. Results of land-mine detection, including performance on blind test lanes, are presented     

机载雷达微弱目标帧间非相参积累与检测技术

微弱目标探测一直是机载雷达,尤其是机载预警雷达面临的重要挑战.针对这一问题提出一种目标帧间非相参积累和检测方法.首先,建立了机载雷达多帧信号采用不同载频和脉冲重复周期场景下的回波信号模型.其次,提出了一种运动目标帧间多普勒校正和距离单元走动补偿方法,使得经过处理后的目标在不同帧数据中位于相同待检测单元.然后,为了避免强...     

Ultra-wideband radar using Fourier synthesized waveforms

Traditional methods of ultra-wideband (UWB) radar signal generation suffer from several disadvantages such as low antenna radiation efficiency and lack of accurate control of signal parameters like pulse shape, pulse repetition interval (PRI), and its spectrum. UWB signals can be generated by expanding the desired radar waveform in a Fourier series and then synthesizing the waveform by generating the individual terms in the expansion from harmonically related oscillators. Signals thus produced overcome the disadvantages of traditional methods of UWB signal generation. Fourier series based method for generation of complex amplitude coded waveforms is developed which can be used to generate time domain equivalent of Barker and other codes for application in radar and communication areas. In radar applications, these coded waveforms, with accurate and stable waveform parameters, shall allow pulse compression and coherent integration. The additional processing gain provided by these operations reduces the need for high peak power in radar transmitters which is one of the bottlenecks in the implementation of operational UWB radars. This paper also describes a UWB radar concept which incorporates Fourier synthesized waveforms. Related digital signal processing issues are also discussed