主元分析在超宽带搜救雷达中的应用

本文利用超宽带搜救雷达对砖墙后有肢体运动的人体进行生命探测,采集雷达回波信号,并利用PCA方法对雷达回波数据进行分解等处理,通过设定自适应阈值,准确判别出雷达回波中是否存在人体体动信号,最后通过实验证明PCA方法可以在超宽带搜救雷达中得到很好的应用。     

雷达式非接触生命参数信号的提取及判别

采用最小均方(LMS)算法,通过对雷达回波信号进行滤波处理来提取生命参数信号.利用超宽带冲击脉冲雷达对砖墙后的人体进行生命探测,采集雷达回波信号,运用LMS算法对回波进行生命参数信号提取.通过一系列的信号预处理后利用LMS算法可以很好地提取出回波中的生命参数信号.     

超宽带搜救雷达的高速数据采集系统设计

利用超宽带雷达进行灾后生命搜救正在成为救灾手段的重要方法之一。其中对雷达回波信号数据的实时采集和存储是最重要的环节之一。但是由于DSP的工作时钟和A／D的采样速度不同，而采用FIFO作为两者的接口，从而提高系统的效率和稳定性。文中介绍了以TMS320VC5509为核心处理器，基于FIFO和DSP的超宽带搜救雷达数据采集系统的硬件和软件设计。实验结果表明，该系统具有速度快、稳定性高、控制方便等特点。     

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。     

一个实用单片数据采集控制系统

研究了一个用单片机控制的雷达回波采集系统，分析了目标雷达回波信号的特性，说明了回波信号采集系统的总体设计和采集控制模块的设计，对控制模拟的软件功能做了简要的介绍。     

K-L变换应用于UWB雷达回波信号的增强

超宽带(Ultra Wideband,UWB)雷达在车辆防撞、废墟营救和反恐穿墙等场景中都扮演着十分重要的角色。但在实际应用中,当接收到的UWB雷达回波信号比较弱或受到外界干扰时,为了得到有用的信息需要对UWB雷达回波信号进行处理。对UWB雷达回波信号进行卡洛南-洛维(Karhunen-Loève,K-L)变换处理,将处理之后的信号与处理之前的信号进行对比,并用运动轨迹的形式来表现。实验结果表明,经K-L变换处理后的UWB雷达回波信号较处理之前有一定的增强。     

超宽带穿墙探测雷达的运动目标检测技术

提出了利用低频超宽带(UWB)脉冲信号实现穿墙探测的设想,研究了超宽带穿墙探测雷达(UWB—TWDR)的运动目标回波信号模型,并基于运动目标回波信号的相关性,利用相干叠加原理对多次观测的结果实现运动目标的检测。最后通过具体的穿透混凝土砖块墙壁实测实验验证了上述设想和算法。     

基于EMD的穿墙雷达墙体回波抑制算法

穿墙探测中墙体回波对于目标检测影响较大。针对超宽带穿墙雷达中去除墙体波的问题,提出采用基于EMD方法提取回波信号中的目标信号分量和墙体回波信号分量,并去墙体回波信号。搭建试验系统并通过处理实测数据,结果表明,提出方法能够有效去除墙体回波信号,并且能够保留目标信号的绝大部分信息,进而对运动人体目标进行检测。     

毫米波汽车防撞雷达系统中数字信号处理机的设计

测距测速是雷达的基本应用之一。文章设计了基于DSP芯片TMS320VC5402的数字信号处理机,对汽车防撞雷达系统接收到的回波信号进行了实时采样和分析并实时计算出目标的距离和速度。实验表明,该信号处理机工作稳定可靠,满足了汽车防撞雷达系统对信号处理的实时性要求。     

超宽带生命探测回波信号的时频分析

针对超宽带雷达在生命探测中如何对回波信号进行分析的问题,提出了该领域最佳时频分析方法——Wigner-Hough变换。主要思路是通过对超宽带雷达信号原理分析,并进行宽相关处理除去各种干扰;然后用短时傅里叶变换、魏格纳变换、Wigner-Hough变换方法对回波信号进行时频分析;利用人的呼吸和心跳数据进行仿真与实验验证,Wigner-Hough变换在时频分析方面有着明显优势。     

基于二维映射的LFM UWB 雷达动目标速度估计

针对线性调频超宽带雷达动目标存在的距离-多普勒耦合以及多普勒色散对测速的影响,该文采用了频率-多普勒平面的2 维映射方法。首先将接收的脉冲串回波,通过快-慢时间的2 维傅里叶变换获得相应的频率-多普勒2 维平面。然后,利用2 维映射处理,将超宽带信号映射为窄带信号,实现多普勒域能量的聚焦。最后,根据映射后的窄带信号对应的多普勒频率获得目标径向速度。该方法不但有效地解决了超宽带雷达多普勒色散对测速的影响,而且规避了由于目标沿距离维的走动引起的慢时间域不能有效的能量积累。通过速度估计值,进行运动补偿后可获得目标距离像。此外,根据相关条件,进一步推导了速度适应范围。仿真实验结果验证了该方法的有效性。      

Ultra-wideband radar signals generated technology with two-channel

Synthesis of ultra-wideband (UWB) linear frequency modulation radar signals is a very important technology for microwave imaging, target identification and detection of low radar-cross-section (RCS) targets. In this paper a new method of UWB radar signals generation with two-channel is presented. The realization structure is given, and the principle of signal synthesis is analyzed. At the same time, an automatic adjustment measure of signal phase is proposed for phase discontinuity of waveform in this method. The simulation experiment and analysis results show that radar signals with large instantaneous bandwidth can be generated by means of this method.     

An efficient FPGA-based implementation of UWB radar system for through-wall imaging

The work presented in this paper aims to develop a low-cost ultra-wideband (UWB) radar system that has the capability to image through the wall of a human target. The proposed radar system relies heavily on a field-programmable gate array (FPGA) platform. The Xilinx FPGA Kintex-7 (KC705) board is employed to integrate the main functionalities of the radar system, such as the generation and acquisition of a UWB signal. The generated signal is a monocycle signal, which has an ultra-wide bandwidth. Due to the UWB nature of this signal, the radar system achieves better penetration ability, as well as high imaging resolution. However, the major challenge of a UWB radar system lies in the stage of digitization, as it requires a high sampling rate analog-to-digital converter (ADC). In fact, such a chip is very expensive. Hence, to reach a high sampling resolution using a low-cost and low-speed ADC, an efficient sampling strategy is implemented. In contrast to other UWB sampling methods, which require a hardware delay line chip, the new sampling scheme depends only on the FPGA firmware to realize a combination of real-time and equivalent-time sampling, which provides better jitter performance. Finally, to demonstrate the imaging capability, experimental tests are conducted in an indoor environment while human targets are located in different places. The measurement results revealed that the proposed radar system has the ability to provide 2D images that accurately determine the location of the target.     

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     

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。     

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。     

Code-Division Multiple Transmission for High-Speed UWB Radar Imaging With an Antenna Array

The ultrawideband (UWB) radar is a promising high-resolution 3-D imaging technique for near targets. We have developed a high-speed imaging algorithm, SEABED, for a UWB pulse radar, a key real-time imaging technology. When the algorithm is applied to UWB, antenna scanning for data acquisition takes significantly longer than calculating the SEABED algorithm itself. This presents a serious problem for the real-time application of UWB radar. In this paper, we use pseudonoise (PN) sequences as the transmitting waveforms, while the original work on the SEABED algorithm assumed impulsive short-wave pulses. Using PN sequences enables us to simultaneously transmit signals with multiple antennas, eliminating the need to scan antennas. We demonstrate that the proposed radar system works well using random sequences to suppress direct waves, which is critical in achieving high speeds for imaging.      

Ultrawide-band coherent processing

In this paper, we develop an approach for estimating the ultrawide-band (UWB) radar signature of a target by using sparse subband measurements. First, we determine the parameters of an appropriate signal model that best fits the measured data. Next, the fitted signal model is used to interpolate between and extrapolate outside of the measurement subbands. Standard pulse-compression methods are then applied to provide superresolved range profiles of the target. The algorithm can automatically compensate for lack of mutual coherence between the radar subbands, providing the potential for UWB processing of real-world radar data collected by separate wide-band radars, because the processing preserves the phase distribution across the measured and estimated subbands, extended coherent processing can be applied to the UWB compressed radar pulses to generate superresolved radar images of the target. Applications of this approach to static test range and field data show promising results     

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.