Modified Omega-K algorithm for processing helicopter-borne frequency modulated continuous waveform rotating synthetic aperture radar data

With appropriate geometry configuration, helicopter- borne rotating synthetic aperture radar （ROSAR） can break through the limitations of monostatic synthetic aperture radar （SAR） on forward-looking imaging. With this capability, ROSAR has extensive potential applications, such as self-navigation and self-landing. Moreover, it has many advantages if combined with the frequency modulated continuous wave （FMCW） technology. A novel geometric configuration and an imaging algorithm for helicopter-borne FMCW-ROSAR are proposed. Firstly, by per- forming the equivalent phase center principle, the separated trans- mitting and receiving antenna system is equalized to the case of system configuration with antenna for both transmitting and receiving signals. Based on this, the accurate two-dimensional spectrum is obtained and the Doppler frequency shift effect in- duced by the continuous motion of the platform during the long pulse duration is compensated. Next, the impacts of the velocity approximation error on the imaging algorithm are analyzed in de- tail, and the system parameters selection and resolution analysis are presented. The well-focused SAR image is then obtained by using the improved Omega-K algorithm incorporating the accurate compensation method for the velocity approximation error. FJnally, correctness of the analysis and effectiveness of the proposed al- gorithm are demonstrated through simulation results.

IMAGING ANALYSIS OF FREQUENCY MODULATION CONTINUOUS WAVE SYNTHETIC APERTURE RADAR IN NEAR RANGE MODE

Frequency-Modulation Continuous-Wave Synthetic Aperture Radar(FMCW SAR)has shown great potential in the applications of civil and military fields because of its easy deployment and low cost.However,most of these work and analysis are concentrated on airborne FMCW SAR,where the characteristics of the imaging geometry and signal are much similar to that of traditional pulsed-SAR.As a result,a series of test campaigns of automobile-based FMCW SAR were sponsored by Institute of Electronics,Chinese Academy of Sciences(IECAS)in the autumn of 2012.In this paper,we analyze the imaging issues of FMCW SAR in automobile mode(named as near range mode),where a vehicle is used as moving platform and a large looking angle is configured.The imaging geometry and signal properties are analyzed in detail.We emphasize the difference of the near range mode from the traditional airborne SAR mode.Based on the analysis,a focusing approach is proposed in the paper to handle the data focusing in the case.Simulation experiment and real data of automobile FMCW SAR are used to validate the analysis.

A TECHNIQUE FOR MEASURING THE LINEARITY OF A LINEARLY FREQUENCY-MODULATED SIGNAL

A technique for measuring the linearity of a linearly frequency-modulated continuous wave (LFM-CW) signal is presented. It uses a delay-line and a mixer to sense the slope of the output of a sweep oscillator, so that the original form of frequency function deviated from idealized linear slope is retrieved by means of spectrum analysis. Consequently,the linearity of the LFM signal is determined. The formulation is performed based on the principle that an angle-modulated signal can be approximated by an amplitude-modulated signal if the modulation coefficient is sufficiently small. To examine the validity of the procedure and to study the effect of each parameter on the accuracy of measurement, a number of computer simulations has been made. The results of simulation show that the error of the measurement is less than 2%.

基于多核DSP的星载双基FMCW SAR成像算法实现

调频连续波(frequency modulated continuous wave,FMCW)合成孔径雷达(synthetic aperture radar,SAR)降低了传感器的峰值传输功率,使系统的重量和成本最小化,被广泛应用于机载平台。将双基地构型与FMCW技术相结合,应用于星载平台,即构成星载双基地FMCW SAR。本文对距离多普勒(range-Doppler,RD)算法进行改进,建立起一种高性能的适宜星载双基地平台的FMCW SAR成像频域算法,这种算法的处理精度明显提高,成像效果更好。基于多核数字信号处理器(digital signal processor,DSP)构建适用于星载双基SAR成像算法的并行处理架构,完成软硬件设计实现。验证了所提软件架构可以满足实时成像需求,以及算法工程化实现的可行性。

多波段FMCW雷达低慢小探测数据集(LSS-FMCWR-1.0)及高分辨微动特征提取方法

无人机等低慢小目标探测对雷达目标检测和识别技术提出了很高的挑战,迫切需要构建相关数据集,支撑低慢小探测技术的发展和应用。该文公开了一个多波段调频连续波(FMCW)雷达低慢小目标探测数据集,基于Ku波段和L波段的FMCW雷达采集6种类型的无人机回波数据,通过雷达调制周期和调制带宽,具备不同时域和频域分辨和测量能力,构建了多波段FMCW雷达低慢小探测数据集(LSS-FMCWR-1.0)。为了进一步提升无人机微动特征提取能力,该文提出基于局部极大值同步提取变换的无人机微动提取和参数估计方法,在短时傅里叶变换的基础上提取时频能量最大值,保留有用信号分量,实现精细化时频表示。基于LSS-FMCWR-1.0进行验证分析,结果表明该方法相较于传统时频方法,熵值平均降低了5.3 dB,旋翼叶长估计误差降低了27.7%,所提方法兼顾高时频分辨率和较高的参数估计精度,为后续目标识别奠定了基础。

基于MIMO-FMCW雷达的多人生命体征检测

针对多输入多输出(MIMO)体制调频连续波(FMCW)雷达难于对室内环境多人生命体征进行准确检测的问题,本文提出一种基于MIMO-FMCW雷达的多人生命体征检测方法。首先对中频信号做距离维快速傅里叶变换(FFT)和Capon角度估计得到对应的距离角度图,利用二维恒虚警检测技术(2D-CFAR)和基于密度的聚类(DBSCAN)算法确定每个目标的距离角度信息,通过线性约束最小方差(LCMV)准则进行数字波束形成得到目标对应的慢时间维信号,并使用反正切函数完成相位信号的提取,最后利用谐波判别准则实现对呼吸和心跳信号频率的估计继而完成对多目标生命体征检测。实验结果表明,谐波判别准则实现了平均相对误差小于10%的呼吸率和心率检测精度,证明了该方法的有效性。

基于延迟断点映射FMCW的双功能雷达通信系统设计

基于调频连续波(Frequency Modulated Continuous Wave, FMCW)的双功能雷达通信(Dual-Functional RadarCommunication, DFRC)系统具有时频利用率高、抗多普勒性能强、距离旁瓣低的特点。现有的FMCW-DFRC波形系统产生双功能性能恶化,并增加通信接收机的链路复杂度。设计了一种基于延迟断点映射(Delayed Breakpoint Mapping, DBM)FMCW的DFRC系统,通过啁啾周期内延迟断点位置的映射和被分割的簇间的相位进行数据调制。通信接收端在载波混频和欠采样后,在数字域实现去啁啾、码片对齐和数据解调,极大降低了接收端生成相干信号和ADC性能的需求。在雷达处理链路中,设计了断点区域删除与拼接(Breakpoint Area Deletion and Splicing, BADS)方案,使DFRC的雷达性能与无调制的FMCW一致。仿真结果表明,与无补偿的方案相比,BADS方案距离图像的副瓣幅度减小约37 dB,且不受调制数据的影响。与现有基于啁啾波形的DFRC方案的通信性能相比,DBM-FMCW降低了约3 dB误符号率。

强干扰下基于三阶互累积量的FMCW雷达信号DOA估计算法

针对车载调频连续波雷达存在相互干扰的实际情况,本文提出了一种基于三阶互累积量的多目标波达方向超分辨估计方法.该方法利用同步采集的阵列信号并根据回波信号和干扰信号的非相关特性,构造三阶互累积量矩阵,随后根据子空间方法获得二维空间谱,实现距离和方位的联合估计.计算机仿真结果表明,本文所提方法能够在抑制强干扰影响的同时实现3°以内多目标识别,与现有超分辨法和重构法相比,具有更高的角度分辨率和估计精度.

Frequency-modulated continuous-wave dual-frequency LIDAR based on a monolithic integrated two-section DFB laser

We demonstrate a high-resolution frequency-modulated continuous-wave dual-frequency LIDAR system based on a monolithic integrated two-section(TS) distributed feedback(DFB) laser. In order to achieve phase locking of the two lasers in the TS-DFB laser, the sideband optical injection locking technique is employed. A high-quality linear frequency-modulated signal is achieved from the TS-DFB laser. Utilizing the proposed LIDAR system, the distance and velocity of a target can be measured accurately. The maximum relative errors of distance and velocity measurement are 1.6% and 3.18%, respectively.

基于FMCW雷达的多人心率呼吸检测

针对目前毫米波雷达应用于多人生命体征检测效果不佳,检测范围小等缺点,提出了一种多人心率呼吸提取分离方法,首先采用Capon波束成形技术对非目标区域信号形成零陷,对目标区域进行提取相位、相位解缠绕操作;其次利用自适应谐波跟踪算法滤除噪声;最后使用粒子群算法和样本熵改进的变分模态分解法(PSO-SE-VMD)对信号进行分解得到模态分量,选取合适的模态分量并通过短时自相关算法提取心率呼吸.实验结果表明,该方法在夹角30°和60°时心率的均方误差分别为5.55和3.15,实现了多人检测并有效提高了检测范围.

基于FMCW的10kV配电电缆故障定位及类型识别方法

为了解决电缆输入阻抗谱法对高阻故障定位距离较短、遮蔽区域大等不足,该文提出一种基于频域反射法的调频连续波(frequency modulated continuous wave,FMCW)电缆故障定位及类型识别方法。首先,依据FMCW电缆故障定位的原理结合电缆分布参数模型进行电缆故障定位仿真,获取电缆的FMCW幅值谱、相位谱。仿真结果表明,幅值谱可用于故障定位,相位谱可用于故障类型识别。根据仿真结果获取不同类型电缆故障(开路、短路、高阻、低阻故障)的相位谱特征。最后,在300m的射频同轴电缆和194m的10k V-XLPE电缆上进行测试,验证所提方法的有效性。实验结果表明,FMCW幅值谱能有效定位电缆的故障;FMCW相位谱的相位特征可以区分开路、短路、高阻、低阻故障。相较于电缆输入阻抗谱法,FMCW方法将高阻故障的检测距离从20 m提高至200m,将输入阻抗法40%的遮蔽区域降至18.2%以内,且对高阻故障的灵敏度从2 kΩ(40Z0)提高至10 kΩ(200Z0)。

空空目标的FMCW ISAR成像研究

相比于传统运动状态下的逆合成孔径雷达(Inverse Synthetic Aperture Radar,ISAR)成像,目标和雷达都在运动的情况下的运动状态更为复杂,存在回波建模难度大、ISAR成像转角过大、成像投影平面不稳定等问题。本文针对机载雷达与空中目标建立了空空目标的运动模型。调频连续波具有大带宽的优点,调频连续波雷达具有体积小、成本低、结构简单等优点。本文采用线性调频连续波体制,研究了FMCW ISAR的自聚焦算法,实现了对空空目标的回波建模与成像。

基于FMCW雷达的多人生命体征检测算法

为实现无感化和长时间的多人生命体征检测,提出一种基于调频连续波(FMCW)雷达的体征检测方法。使用单元平均恒虚警率(CA-CFAR)算法实现多个目标的定位和区分;针对呼吸谐波对心率信号的干扰现象,采用最小均方(LMS)算法对呼吸谐波进行自适应噪声抵消,提高心率信号信噪比;使用高分辨率的MUSIC算法实现呼吸和心率频率的估计。实验表明,该算法能够对多个目标准确地估计呼吸率和心率,且准确率优于快速傅里叶变换(FFT)和自相关等算法。

多普勒模糊下的FMCWMIMO雷达目标参数估计方法

近年来,随着智能驾驶技术的不断发展,毫米波雷达作为汽车安全控制系统的核心组件受到了广泛关注。时分复用(TDM)多输入多输出(MIMO)调频连续波(FMCW)雷达因具有低硬件成本和高角度分辨率的优势而被广泛应用于汽车雷达,但TDMMIMO在实际应用中还存在对运动目标检测易出现速度模糊和角度模糊问题,导致检测误差变大,对于自动驾驶场景存在一定的安全隐患。为解决上述TDM MIMO FMCW雷达存在检测误差高的问题,提出了在多普勒模糊下的FMCW MIMO雷达目标参数估计方法,在不增加额外硬件开销的前提下,可确保算法在低复杂度下提升监测的时效性,解决了速度模糊和相位偏移问题;利用加Kaiser窗FFT波束形成方法对目标角度进行测量,从而得到更精准的目标信息。仿真和实验结果验证了所提方法的有效性。

基于二阶Keystone变换的FMCWSAR动目标成像与参数估计

本文研究了一种适用于调频连续波(Frequency Modulated Continuous Wave,FMCW)合成孔径雷达(Synthetic Aperture Radar,SAR)的地面动目标成像与参数估计的方法。首先,建立FMCW SAR系统下的动目标回波模型,通过多普勒频移补偿和时频代换,提出了一种基于二阶Keystone变换校正动目标回波距离弯曲的方法。其次,用Hough变换去估计动目标距离向速度,并据此进行距离走动校正。最后,采用Wigner-Hough变换估计动目标的多普勒调频率,通过补偿二次和三次多普勒相位实现动目标的精确聚焦。仿真结果表明:该方法对参数估计有较高的准确性,同时估计的参数对动目标成像有较好的聚焦效果。

基于VMD-SWT联合算法的FMCW雷达生命体征检测

针对雷达生命体征检测中心跳信号易受到呼吸谐波干扰的现象,提出了一种基于变分模态分解(variational mode decomposition,VMD)与同步压缩小波变换(synchrosqueezed wavelet transform,SWT)的联合算法。该方法利用VMD从胸部位移信号中分离出呼吸信号和心跳信号,并对心跳信号使用SWT进一步处理,以获得心跳信号的时频信息。实验结果表明,该方法能够有效分离呼吸信号和心跳信号,并准确提取心跳信号的时频信息,降低呼吸谐波对检测结果的干扰,心率检测结果的均方根误差为2.12次/min。

基于FMCW雷达的多通道特征融合人体动作识别方法

针对采用单一特征进行人体动作识别准确率不高的问题,提出了一种基于调频连续波(Frequency Modulated Continuous Wave,FMCW)雷达的多通道特征融合人体动作识别方法。通过对FMCW雷达回波数据进行预处理,得到人体动作的距离参数与多普勒参数,构建出距离-时间特征谱图和多普勒-时间特征谱图数据集。为了进行人体动作特征的充分提取与精确识别,改进了单通道输入的传统卷积神经网络结构,把部分残差连接结构和跨阶段部分连接结构进行了优化应用至雷达人体动作识别领域,设计出端到端的CSP-FCNN(Cross Stage Partial-Fusion Convolutional Neural Network)多通道融合卷积神经网络。采用公开数据集进行实验,结果表明所提方法有效解决了单一特征动作识别信息量欠缺以及网络提取特征不充分的问题,识别准确率较单一特征识别方法提高了5%以上。

Frequency Sweep Linearization for Semiconductor Laser Using a Feedback Loop Based on Amplitude-Frequency Response

A scheme of frequency sweep linearization of semiconductor lasers using a feed-back loop based on amplitude-frequency response is demonstrated in this paper. The beat frequency signal is obtained by self-heterodyne detection. The frequency changes are converted to the envelope of beat frequency signal after amplitude-frequency response. The active frequency sweep linearization is realized by feeding envelope deviations back to the drive currents of the lasers by a feedback loop. A simulation model is built to verify this scheme by Simulink. This scheme does not need high-performance, expensive lasers, complex linearization or tedious post-processing processes, which are of great significance for related applications.

基于多域融合的FMCW雷达手势识别方法

为了提高对动态手势动作的识别性能,文中提出一种基于多域融合的调频连续波(Frequency Modulated Continuous Wave,FMCW)雷达手势识别方法。首先,利用FMCW雷达对不同手势动作进行探测并收集回波数据;然后,对接收的回波数据进行预处理得到目标的距离-时间矩阵、多普勒-时间矩阵和固定帧时间长度的距离-多普勒-帧三维矩阵,将每个手势动作对应的三种数据矩阵输入到三通道卷积神经网络(Convolutional Neural Networks,CNN)中进行手势特征提取;最后,采用可训练的权值矩阵对各个数据域提取的特征向量进行融合得到手势动作分类结果。实测数据处理结果表明所提基于加权融合的三通道CNN手势识别方法对八种手势动作的分类平均准确率达到98.45%,与传统的平均融合和拼接融合方式相比有效提高了对手势动作的分类能力。

FMCW雷达河面污染物检测系统的设计与实现

针对河面污染监测精度低、实时监测差的问题,通过对调频连续波(FMCW)的分析和研究,设计实现了一种FMCW探测雷达。通过ZedBoard信号处理板对污染物的I、Q两路差频信号做两次FFT算法处理,测得目标污染物的速度和距离信息,速度最大误差为6%,距离最大误差为4.9%。测试结果表明,其可分辨河面污染目标物体,具有较好的分辨能力,同时有实时监控告警提醒能力,可应用于河面污染物探测中,提高了河面污染物探测效率。