一种基于动目标聚焦的SAR-GMTI方法

由于输入信杂噪比(Signal to Clutter Noise Ratio, SCNR)较低,杂波抑制后超高频(Ultra-High Frequency, UHF)波段合成孔径雷达(Synthetic Aperture Radar, SAR)图像中剩余静止目标杂波导致系统虚警概率较高。该文提出一种动目标筛选方法,能够判断恒虚警概率(Constant False Alarm Rate, CFAR)检测器检测到的目标是否为动目标。提出一种动目原始数据恢复方法,能够从整幅SAR图像中恢复任意孤立点的多普勒相位历史。采用距离多普勒处理对恢复的数据成像,然后采用方位自聚焦处理对所成子图像进行重新聚焦。如果子图像中目标为静止目标,则聚焦前后子图像不变,否则图像被重新聚集。通过检测图像的变化可以排除虚假动目标。仿真及实测数据处理结果说明了该方法的有效性。     

多通道SAR近岸水面区域模糊杂波抑制方法

在方位多通道合成孔径雷达(SAR)体制下,针对近岸水面区域出现的强模糊地杂波抑制问题,该文分析推导了模糊杂波的多通道导向矢量,建立了近岸水面区域的SAR图像域多通道信号模型。以推导的导向矢量和建立的模型为依据,提出了适合近岸水面区域的模糊杂波抑制方法,分析了方位多通道空域采样带来的空域模糊对模糊杂波的影响,在此基础上,对该类背景下的动目标检测性能进行了仿真分析。仿真实验验证了该算法的有效性。     

利用基于导数更新的双基机载雷达杂波距离依赖性补偿方法

该文提出了两种利用基于导数更新(DBU)的双基机载雷达杂波距离依赖性补偿新方法,分别以接收载机方向图主瓣方向的接收斜距和接收载机方向图主瓣方向的接收俯仰角余弦为更新变量,利用该方法对回波数据进行补偿后,能够有效降低双基机载雷达杂波的距离依赖性,进而大大提高空时自适应处理 (STAP)的地面动目标检测(GMTI )性能。仿真数据处理结果证明了所提方法的有效性。     

MIMO SAR OFDM chirp waveform design and GMTI with RPCA based method

Multiple-input multiple-output synthetic aperture radar (MIMO SAR) has drawn wide attention for its increased degrees of freedom (DOFs) compared to the traditional multi-channel SAR (MC-SAR) system. The MIMO SAR system, which makes each antenna illuminate one subswath, can widen the range swath without decreasing PRF. One of the foremost tasks involved in the MIMO SAR system is the waveform design at the transmitter. Moreover, at the receiver, how to accurately separate the auto-correlation signal from the cross-correlation interferences is the other important issue. In this paper, an orthogonal frequency division multiplexing (OFDM) chirp signal designing method is firstly proposed, which is based on low cross-correlation interferences and good peak-to-sidelobe ratio (PSLR) rules. Using the designed OFDM chirp signals, the focused signal of MIMO SAR system matched the robust principal component analysis (RPCA) basic model. The moving target (sparse signal), clutter (low-rank signal) and noise (noise signal) can be separated directly. Hence, RPCA based method can be employed for ground moving target indication (GMTI) with no need for extracting the matched signal or suppressing the unmatched interferences. Extensive simulations demonstrate the effectiveness of the waveform designing method and GMTI with RPCA based method for MIMO SAR system.     

双基机载雷达GMTI的参数自适应匹配滤波器性能分析与定阶方法研究

在双基机载雷达的地面动目标检测中,参数自适应匹配滤波器（PAMF）方法是一种很有效的方法。该文从矩阵扰动的角度分析出了PAMF方法性能较好的本质原因,并为PAMF方法的阶数确定给出了依据。该文内容将有助于双基机载雷达系统中关于PAMF方法的研究。     

长相关积累STAP处理的星载SAR-GMTI

目前多通道STAP多应用在短相干脉冲积累(CPI)模式的非成像体制雷达地杂波抑制,而对长CPI的SAR成像体制下的讨论较少。文中首先分析两种体制下STAP采用的不同信号模型,研究CPI对回波统计特性的影响和两种体制目标功率谱的差异。然后讨论SAR成像体制下STAP的应用,分析空时去相干性的影响。指出星载非平稳杂波环境中长CPI多普勒后处理的优势:既能有效降低杂波秩,减小样本支持数,同时减弱对空时去相关源的敏感性,又可得到动目标SAR图像。最后给出仿真实例。     

星载稀疏阵扫描模式干涉雷达动目标检测研究

地面动目标检测(GMTI)是星载分布式雷达的重要应用之一,利用星载稀疏阵可增加系统虚拟孔径,以改善动目标检测性能.扫描模式干涉雷达(Scanning Pattern Interferometric Radar,简称SPIR)是一种雷达天线阵波束扫描的新型GMTI雷达,用点扩展函数(Point Spread Function,简称PSF)与扫描结果进行解卷积,就能恢复出地物后向散射系数,然后利用杂波位置来检测动目标.本文分析了SPIR方法的基本原理,并对有不同位置误差的阵列进行了SPIR仿真,比较仿真结果发现,在一定误差范围内,准确测量孔径实际位置比精确控制孔径位置更重要.     

Blind velocities mitigation for MIMO GMTI radar with Doppler division multiple access waveforms

Multiple-input multiple-output (MIMO) radar with multiple transmitters and multiple receivers can achieve a larger virtual antenna array and more system degrees of freedom; thus applying it to ground moving target indication (GMTI) radar can improve the performance of GMTI. Doppler division multiple access (DDMA) waveforms are approximately orthogonal providing good minimum detectable velocity (MDV) performance. However, in such DDMA systems, a sufficient pulse repetition frequency (PRF) design freedom is required. Furthermore, these waveforms suffer from blind velocities which are serious problems, especially in radar systems with high carrier frequency or low PRF. This paper analyses the blind velocities problem and show that blind velocities are relative to variation of the PRF and/or the carrier frequency. Variable PRF techniques are widely used in conventional GMTI radar including multiple PRFs and variable pulse repetition intervals (PRI). Combined with the characteristics of the DDMA MIMO GMTI radar, this paper proposed two methods to mitigate blind velocities: “multi-PRF DDMA” which employs multiple PRFs over successive coherent processing intervals, and “PRI-dithered DDMA” which employs nonuniform sampling by dithered PRI in slow time. Simulation results demonstrate that both the methods are effective ways to mitigate blind velocities in DDMA MIMO GMTI radar systems.     

Clutter suppression method for heterogeneous environment

Clutter suppression is a key process in ground moving target indication (GMTI). Adaptive filtering is an effective method for clutter suppression but the performance degrades severely in heterogeneous clutter environment. To solve this problem, a new clutter suppression method is proposed. The approach uses subspace tracking technique to update clutter subspace of different clutter patches which may mitigating the heterogeneous effects. Simulation results illustrate that the method performs well when lacking of the independent and identically distributed (i.i.d.) samples.     

基于DBF-SCORE的Ka SAR-GMTI信号处理方法研究*

在SAR信号处理中为增大接收增益,提高系统回波的信噪比,可利用数字波束形成(DBF)技术(扫描接收技术)生成灵活控制的高增益窄波用于多通道接收、处理回波信号。分析并推导了距离向多通道的回波信号,然后详细分析了基于偏置相位中心天线（DPCA）的SAR GMTI处理方法。在此基础上给出了一种使用DPCA杂波抑制技术处理基于时变加权DBF SCORE回波的Ka SAR GMTI处理方法,并给出了系统实现原理。与其他SAR GMTI处理方法相比较,使用DBF技术可以提升系统信噪比,有助于改善杂波抑制性能。通过仿真,验证了用DPCA技术处理基于DBF动目标回波的有效性。