Multichannel high-resolution and wide-swath(HRWS)imaging is an advanced digital beamforming technique for future synthetic aperture radar(SAR)systems.However,radio frequency interference(RFI)is a critical concern for ...Multichannel high-resolution and wide-swath(HRWS)imaging is an advanced digital beamforming technique for future synthetic aperture radar(SAR)systems.However,radio frequency interference(RFI)is a critical concern for HRWS SAR missions,which distorts measure-ments and produces image artifacts.In this paper,the spatial cross-correlation coefficients of multichannel HRWS SAR signals are investigated for RFI detection.It is found when the two channels are correlated,RFI-polluted areas present lower coherence values than non-polluted areas in the same scenarios,which makes previous methods fail.Further,this paper studies the case of two fully decorrelated channels to maximize the coherence difference among RFI and target echoes,and RFI detection is realized by exploiting the anomaly value of coherence.Experimental results of real air-borne multichannel SAR data demonstrate that the RFI can be detected successfully.展开更多
射频干扰(radio frequency interference,RFI)对L波段综合孔径辐射计遥感数据造成了严重污染,降低了产品质量。RFI检测定位是处理RFI的关键步骤。传统的基于亮温图像的定位算法受到仪器角分辨率的限制,无法有效分离相邻的RFI。为了实现...射频干扰(radio frequency interference,RFI)对L波段综合孔径辐射计遥感数据造成了严重污染,降低了产品质量。RFI检测定位是处理RFI的关键步骤。传统的基于亮温图像的定位算法受到仪器角分辨率的限制,无法有效分离相邻的RFI。为了实现更高的空间分辨率,基于子空间分解技术的多信号分类(multiple signal classification,MUSIC)算法被提出。然而,当亮温图像的信噪比较低时,背景和噪声对子空间分解的准确性影响较大,进而降低了MUSIC算法的定位性能。文章通过结合亮温图像和子空间分解两种方法的优点,提出了一种融合改进定位方法。该方法通过在亮温图像域中消除背景场景、增强目标射频干扰,2次提高了图像信噪比,在频域中,利用子空间分解和MUSIC算法实现超分辨率和高精度定位。通过对土壤湿度和海洋盐度(soil moisture and ocean salinity,SMOS)卫星数据进行实验和仿真验证,证明了文章提出的方法在低信噪比情况下优于传统的MUSIC算法和基于亮温的定位算法。此外,在对多个弱RFI源的定位上,该方法的定位精度也优于基于点源波纹的弱RFI检测定位算法。展开更多
The aim of this project is to develop a novel approach for optimizing design resin film infusion (RFI) processing parameters by manufacturing T-shaped composite panel. The dimensional accuracy was selected as the obje...The aim of this project is to develop a novel approach for optimizing design resin film infusion (RFI) processing parameters by manufacturing T-shaped composite panel. The dimensional accuracy was selected as the objective function. By investigating the rheological properties of resin film, the compaction behavior of fiber preform and characteristics of RFI process, an optimal mathematical model was established, it was found that the numerical results obtained from the RFICOMP program package have good consistency with the experimental results, and this optimization procedure can be applied to other composites manufacture processes.展开更多
冷湖地区因干旱少雨、晴天数多、云量覆盖少等特点,引起了天文学家的高度关注。2018年开始在冷湖赛什腾山开展光学视宁度测量,几年测量结果表明赛什腾山光学台址特性可比肩世界著名光学台址。为进一步了解赛什腾天文台址的电磁环境特性...冷湖地区因干旱少雨、晴天数多、云量覆盖少等特点,引起了天文学家的高度关注。2018年开始在冷湖赛什腾山开展光学视宁度测量,几年测量结果表明赛什腾山光学台址特性可比肩世界著名光学台址。为进一步了解赛什腾天文台址的电磁环境特性,开展了无人值守无线电干扰RFI(Radio Frequency Interference)测量设备的研制以及在赛什腾山天文台址的电磁环境监测。文章主要介绍基于研制的0.1~18 GHz频段RFI测量系统,在冷湖赛什腾山天文台址规划D点(海拔4055 m)开展为期超过一年的RFI测量,以及测量结果的评估。展开更多
基金supported by the National Natural Foundation of China(Nos.41001282,40871205,and 62271408)partly by Shanghai Aerospace Science and Technology Innovation Fund(No.SAST2021-044)。
文摘Multichannel high-resolution and wide-swath(HRWS)imaging is an advanced digital beamforming technique for future synthetic aperture radar(SAR)systems.However,radio frequency interference(RFI)is a critical concern for HRWS SAR missions,which distorts measure-ments and produces image artifacts.In this paper,the spatial cross-correlation coefficients of multichannel HRWS SAR signals are investigated for RFI detection.It is found when the two channels are correlated,RFI-polluted areas present lower coherence values than non-polluted areas in the same scenarios,which makes previous methods fail.Further,this paper studies the case of two fully decorrelated channels to maximize the coherence difference among RFI and target echoes,and RFI detection is realized by exploiting the anomaly value of coherence.Experimental results of real air-borne multichannel SAR data demonstrate that the RFI can be detected successfully.
文摘射频干扰(radio frequency interference,RFI)对L波段综合孔径辐射计遥感数据造成了严重污染,降低了产品质量。RFI检测定位是处理RFI的关键步骤。传统的基于亮温图像的定位算法受到仪器角分辨率的限制,无法有效分离相邻的RFI。为了实现更高的空间分辨率,基于子空间分解技术的多信号分类(multiple signal classification,MUSIC)算法被提出。然而,当亮温图像的信噪比较低时,背景和噪声对子空间分解的准确性影响较大,进而降低了MUSIC算法的定位性能。文章通过结合亮温图像和子空间分解两种方法的优点,提出了一种融合改进定位方法。该方法通过在亮温图像域中消除背景场景、增强目标射频干扰,2次提高了图像信噪比,在频域中,利用子空间分解和MUSIC算法实现超分辨率和高精度定位。通过对土壤湿度和海洋盐度(soil moisture and ocean salinity,SMOS)卫星数据进行实验和仿真验证,证明了文章提出的方法在低信噪比情况下优于传统的MUSIC算法和基于亮温的定位算法。此外,在对多个弱RFI源的定位上,该方法的定位精度也优于基于点源波纹的弱RFI检测定位算法。
文摘The aim of this project is to develop a novel approach for optimizing design resin film infusion (RFI) processing parameters by manufacturing T-shaped composite panel. The dimensional accuracy was selected as the objective function. By investigating the rheological properties of resin film, the compaction behavior of fiber preform and characteristics of RFI process, an optimal mathematical model was established, it was found that the numerical results obtained from the RFICOMP program package have good consistency with the experimental results, and this optimization procedure can be applied to other composites manufacture processes.
文摘冷湖地区因干旱少雨、晴天数多、云量覆盖少等特点,引起了天文学家的高度关注。2018年开始在冷湖赛什腾山开展光学视宁度测量,几年测量结果表明赛什腾山光学台址特性可比肩世界著名光学台址。为进一步了解赛什腾天文台址的电磁环境特性,开展了无人值守无线电干扰RFI(Radio Frequency Interference)测量设备的研制以及在赛什腾山天文台址的电磁环境监测。文章主要介绍基于研制的0.1~18 GHz频段RFI测量系统,在冷湖赛什腾山天文台址规划D点(海拔4055 m)开展为期超过一年的RFI测量,以及测量结果的评估。
