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     

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     

无载波超宽带雷达时域多普勒处理

从多散射中心目标的回波模型入手，分析了无载波超宽带雷达目标运动引起的多普勒效应，得出了无载波超宽带雷达多普勒效应的时域表现形式-多普勒时移，对一种基于多普勒时移的时域多普勒处理器进行了Matlab仿真。结果表明：利用多普勒时移可有效检测出目标速度，并且不存在盲速。     

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。     

基于MIMO雷达的相干分布式目标 参数估计Cramer-Rao下界

 本文研究了MIMO雷达对相干分布式目标参数估计的Cramer-Rao下界(CRB).首先,给出相干分布式目标的MIMO雷达信号模型,推导出目标参数估计CRB的一般关系式;然后,给出在一个分布式目标、点目标和目标部分信息已知等特殊情况下的CRB;其次,讨论了MIMO雷达CRB的性质;最后,进行计算机仿真试验,研究不同条件下的MIMO雷达性能.结果表明由于具有避免波束形状损失等优点,MIMO雷达对相干分布式目标的参数估计CRB性能优于普通相控阵雷达.本文的研究揭示了MIMO雷达的相干分布式目标参数估计性能.     

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。     

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。     

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.     

三频段准连续波雷达信号目标检测性能分析

准连续波雷达是一种低截获概率雷达,结合了脉冲雷达收发隔离和连续波雷达截获概率低的优点,但其检测性能的优劣很大程度依赖于信号形式,普通的编码信号和线性调频信号已经不能满足其对目标探测的要求。为解决这个问题,设计了一种三频段信号和与之相应的收发系统,对系统结构及三频段信号的参数选择原则、目标检测原理、模糊函数、抗近距离盲区性能做了详细分析,并指出了三频段信号相对于相位编码信号和分时发射信号的优势所在,最后通过仿真证明,将三频段信号应用于准连续波体制雷达中时能准确探测目标,得到目标的各个参数并且能有效消除近距离盲区。     

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.     

单脉冲雷达抗同频干扰措施分析

针对火箭测控链多台同频雷达合作跟踪同一个箭上目标时产生的同频干扰,文中从雷达特殊时序、火箭残骸信号等因素对前卫门的影响着手,深入分析了前卫门机制的缺陷,设计通过适当调整雷达发射信号的特征,改善雷达分辨非相参干扰信号的能力,进而彻底消除现行单脉冲雷达在应答式跟踪时产生卫门盲区的问题,以及同频干扰带来的影响,为下一步雷达设计提供参考。     

高频线性调频雷达的高精度目标瞬时距离估计

高频线性调频雷达的距离量化步长通常为几公里,相对舰船目标尺度而言测距精度非常低.本文分析了目标的距离谱及目标的运动对其瞬时幅度的影响,提出了一种新的高精度目标瞬时距离估计方法.该方法首先确定目标的时频分布,然后通过相邻三个距离点上目标的瞬时幅度比拟合出目标的瞬时距离.计算机仿真实验和雷达实测信号处理结果表明该方法是有效的,它大大提高了高频雷达的目标测距精度.     

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.     

Faraday效应对空间目标探测雷达的影响

分析了电离层Faraday旋转效应对空间目标探测雷达的影响。从磁离子理论出发,结合电离层模型和地球磁场模型,使用了一种快速的Faraday旋转角计算模型,并与传统使用的经验计算方法进行了比较,表明该方法普适性强,更适用于中国地区。针对当前国际上典型的空间目标探测雷达工作频段,选取我国海口（低纬地区）和长春（中纬地区）为代表,分别计算了太阳活动极大年和极小年间的Faraday旋转角,给出了仿真结果并进行分析,表明Faraday旋转效应给线极化方式雷达带来明显的回波能量损失。在进行雷达设计时,需要将该效应与雷达系统性能综合考虑,采用合适的天线极化方式。     

Chaos UWB Radar for Through-the-Wall Imaging

In this paper, we propose to apply a novel chaos-based ultra-wide band (UWB) radar for through-the-wall imaging. The proposed chaos modulation offers superior resolution compared to conventional UWB radars when applied for through-the-wall imaging. A noncoherent receiver is designed based on expectation maximization (EM) algorithm. The theoretical detection performance is derived for through-the-wall detection in the presence and absence of room reverberations as a function of dielectric properties of walls, targets, and their geometry illustrating the robustness of the proposed modulation against room reverberations. The resolution of the proposed modulation is analyzed theoretically and verified through simulations for different wall materials. Numerical electromagnetic simulations using finite difference time domain (FDTD) method are performed to confirm the obtained theoretical results. From the theoretical and simulation analysis, we find that the proposed chaos-based pulse amplitude modulated ultra-wide band (CPAM-UWB) radar has better detection performance, penetrating ability and imaging performance compared to other conventional through-the-wall imaging radars.      

宽带和窄带雷达在噪声中的检测性能比较

宽带雷达相比于窄带雷达具有更高的距离分辨率,因此目标起伏较小。分析了宽带无起伏目标模型,宽带瑞利起伏目标模型和宽带莱斯起伏目标模型的宽带和窄带雷达的回波特性,并推导了它们在高斯白噪声中的检测概率。检测性能曲线表明,在高检测概率时,宽带雷达比窄带雷达具有更好的检测性能;但是随着雷达分辨率的提高,宽带雷达能量积累检测器的积累损失也增加,这个因素使得当雷达带宽增加到一定程度后宽带雷达相对于窄带雷达在检测方面的优势失去意义。     

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.     

超宽带汽车防撞雷达的设计

将超宽带技术引入汽车防撞雷达领域。介绍了超宽带汽车防撞雷达对发射信号的要求，给出完整的系统框图和说明，介绍了通过PCI7300A数据采集卡对AD转换后的回波信号进行实时采集，并对采集到的数据进行时域处理的具体过程。重点提出了利用回波位置进行目标识别，以及利用3根接收天线来测角的新方法。针对汽车防撞的使用环境，只对存在相对运动的目标进行检测，从而降低了信号处理的难度，提高了图像的刷新率。     

雷达探鸟技术发展与应用综述

探鸟雷达已成为机场鸟击防范、风力发电场鸟击风险评估、鸟类自然保护区鸟情观测与科学研究的重要工具。文中首先论述了探鸟雷达的主要组成部分。然后,分析了地面杂波、空域杂波和其他无关目标对探鸟雷达探测效果的影响,进而介绍了传统的杂波抑制方法和相参雷达杂波抑制技术,以及先进的探鸟雷达采用的目标检测、目标跟踪、目标显示、数据记录和雷达组网等数据处理技术。接着,给出了当前的探鸟雷达能够获取的目标轨迹、回波大小、回波强度、信号波动、飞行速度、飞行高度等反映飞鸟目标特性的主要指标。最后,描述了国内外四种典型雷达探鸟系统,并针对雷达探鸟技术的未来发展提出了一些思考及可行性建议。