随着无线电技术的发展,射频干扰(radio frequency interference,RFI)对射电天文观测的影响越来越大,尤其是周期性RFI对天文观测的影响越来越显著。本文围绕宽带、高时间分辨率频谱数据,采用阈值计算、噪声通道过滤、快速傅里叶变换、周...随着无线电技术的发展,射频干扰(radio frequency interference,RFI)对射电天文观测的影响越来越大,尤其是周期性RFI对天文观测的影响越来越显著。本文围绕宽带、高时间分辨率频谱数据,采用阈值计算、噪声通道过滤、快速傅里叶变换、周期计算、通道合并、来源分析和模板库建立等步骤,提出一种面向宽带频谱序列的周期RFI统计方法。将该方法应用于新疆天文台南山观测站26 m射电望远镜(Nan Shan 26 m Radio Telescope,NSRT)脉冲星观测终端数据,有效地检测并提取出了频谱序列中的周期性RFI,可为进一步电磁干扰缓解提供数据支撑。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
Radio frequency interference(RFI)will pollute the weak astronomical signals received by radio telescopes,which in return will seriously affect the time-domain astronomical observation and research.In this paper,we use...Radio frequency interference(RFI)will pollute the weak astronomical signals received by radio telescopes,which in return will seriously affect the time-domain astronomical observation and research.In this paper,we use a deep learning method to identify RFI in frequency spectrum data,and propose a neural network based on Unet that combines the principles of depthwise separable convolution and residual,named DSC Based Dual-Resunet.Compared with the existing Unet network,DSC Based Dual-Resunet performs better in terms of accuracy,F1 score,and MIoU,and is also better in terms of computation cost where the model size and parameter amount are 12.5%of Unet and the amount of computation is 38%of Unet.The experimental results show that the proposed network is a high-performance and lightweight network,and it is hopeful to be applied to RFI identification of radio telescopes on a large scale.展开更多
Radio Frequency Interferences (RFI), such as strong Continuous Wave Interferences (CWI), can influence the Quality of Service (QoS) of communications, increasing the Bit Error Rate (BER) and decreasing the Signal-to-N...Radio Frequency Interferences (RFI), such as strong Continuous Wave Interferences (CWI), can influence the Quality of Service (QoS) of communications, increasing the Bit Error Rate (BER) and decreasing the Signal-to-Noise Ratio (SNR) in any wireless transmission, including in a Digital Video Broadcasting (DVB-S2) receiver. Therefore, this paper presents an algorithm for detecting and mitigating a Multi-tone Continuous Wave Interference (MCWI) using a Multiple Adaptive Notch Filter (MANF), based on the lattice form structure. The Adaptive Notch Filter (ANF) is constructed using the second-order IIR NF. The approach consists in developing a robust low-complexity algorithm for removing unknown MCWI. The MANF model is a multistage model, with each stage consisting of two ANFs: the adaptive IIR notch filter <i>H</i><i><sub>l</sub></i>(<i>z</i>) and the adaptive IIR notch filter <i>H</i><i><sub>N</sub></i>(<i>z</i>), which can detect and mitigate CWI. In this model, the ANF is used for estimating the Jamming-to-Signal Ratio (JSR) and the frequency of the interference (<i>w(0)</i>) by using an LMS-based algorithm. The depth of the notch is then adjusted based on the estimation of the JSR. In contrast, the ANF <i>H</i><i><sub>N</sub></i>(<i>z</i>) is used to mitigate the CW interference. Simulation results show that the proposed ANF is an effective method for eliminating/reducing the effects of MCWI, and yields better system performance than full suppression (<i>k<sub>N</sub></i>=1) for low JSR values, and mostly the same performance for high JSR values. Moreover, the proposed can detect low and high JSR and track hopping frequency interference and provides better Bit error ratio (BER) performance compared to the case without an IIR notch filter.展开更多
We describe the fabrication of high performance YBa2Cu3O7-δ （YBCO） radio frequency （RF） superconducting quantum interference devices （SQUIDs）, which were prepared on 5 mm×5 mm LaAlO3 （LAO） substrates by ...We describe the fabrication of high performance YBa2Cu3O7-δ （YBCO） radio frequency （RF） superconducting quantum interference devices （SQUIDs）, which were prepared on 5 mm×5 mm LaAlO3 （LAO） substrates by employing stepedge junctions （SEJs） and in flip-chip configuration with 12 mm×12 mm resonators. The step in the substrate was produced by Ar ion etching with step angles ranging from 47° to 61°, which is steep enough to ensure the formation of grain boundaries （GBs） at the step edges. The YBCO film was deposited using the pulsed laser deposition （PLD） technique with a film thickness half of the height of the substrate step. The inductance of the SQUID washer was designed to be about 157 pH. Under these circumstances, high performance YBCO RF SQUIDs were successfully fabricated with a typical flux-voltage transfer ratio of 83 mV/φ0, a white flux noise of 29 μφ0/√Hz, and the magnetic field sensitivity as high as 80 fT/√Hz. These devices have been applied in magnetocardiography and geological surveys.展开更多
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
从海量的天文观测数据中快速搜寻罕见的快速射电暴(Fast Radio Burst,FRB)事件,干扰缓解是其中一项关键而具有挑战的工作.射频干扰(Radio Frequency Interference,RFI)会淹没真实的天文事件,还会导致搜寻管线输出大量的假阳性候选体.由...从海量的天文观测数据中快速搜寻罕见的快速射电暴(Fast Radio Burst,FRB)事件,干扰缓解是其中一项关键而具有挑战的工作.射频干扰(Radio Frequency Interference,RFI)会淹没真实的天文事件,还会导致搜寻管线输出大量的假阳性候选体.由于干扰来源及其种类的复杂性,目前并没有一种通用的方法可以解决这个问题.为了降低干扰对FRB观测搜寻的影响,分析和研究了南山26m射电望远镜L波段观测数据中的干扰情况,针对主要的窄带干扰和宽带干扰建立了3层次的干扰缓解处理流程,从而有效缓解了观测数据的干扰污染情况.将该流程嵌入到FRB色散动态谱搜寻(Dispersed Dynamic Spectra Search,DDSS)管线中,实验结果表明,搜寻管线的检测率和检测精度得到了进一步的提高.该方法为FRB观测数据干扰缓解处理提供了有价值的参考.展开更多
来自人造卫星的信号是射电天文观测面临的主要射频干扰(radio frequency interference,RFI)之一,这些RFI会将天文信号掩埋,为天文信号的搜寻和分析带来困扰。为了缓减卫星对天文观测的影响,我们在之前的工作中为500 m口径球面射电望远镜...来自人造卫星的信号是射电天文观测面临的主要射频干扰(radio frequency interference,RFI)之一,这些RFI会将天文信号掩埋,为天文信号的搜寻和分析带来困扰。为了缓减卫星对天文观测的影响,我们在之前的工作中为500 m口径球面射电望远镜(Five-hundred-meter Aperture Spherical radio Telescope,FAST)开发了卫星电磁干扰监测软件,主要包括卫星数据库、观测模块和监测模块。近年来随着多个巨型卫星星座的规划发射以及望远镜观测模式的增多,卫星对射电天文观测的影响更为复杂,已有的软件已经不能满足实际的需要。为此,本文在单个卫星干扰分析的基础上提出了卫星星座的干扰评估方法,并对已有监测软件进行了升级,升级后卫星数据库覆盖更多的在轨卫星及星座信息且能够自动化更新,观测模块能够支持更多种观测模式下的卫星过境预测和干扰评估。在实际天文观测中,通过接在FAST接收机上的频谱仪数据对软件的干扰预测结果进行了实验验证,结果证明升级后的软件能够在多种观测模式下预测可能威胁的卫星以及对应的过境时间,为望远镜观测规划的调整、卫星干扰的规避和接收系统的保护提供重要的支撑。展开更多
由于射频信号的广泛存在,合成孔径雷达(Synthetic Aperture Radar,SAR)在成像的过程中容易受到各类射频干扰(Radio Frequency Interference,RFI)的影响,这会导致获得的SAR图像质量下降,从而对后续的信息提取和目标识别等过程产生很大的...由于射频信号的广泛存在,合成孔径雷达(Synthetic Aperture Radar,SAR)在成像的过程中容易受到各类射频干扰(Radio Frequency Interference,RFI)的影响,这会导致获得的SAR图像质量下降,从而对后续的信息提取和目标识别等过程产生很大的影响。因此,衡量SAR图像受射频干扰的影响程度就尤为重要。然而,现有评估方法的鲁棒性通常较低,并且在评估时未考虑SAR图像受RFI影响的区域大小,因此本文提出了干扰区域⁃强度特征提取与联合评估网络。所提出的网络包含两个模块,干扰强度特征提取模块用于提取输入SAR图像中的干扰强度信息,干扰区域特征提取模块则侧重于干扰区域大小与边界信息的获取。由于SAR图像的尺寸一般比较大,因此本文在干扰强度特征提取模块中采用了多级残差和多层特征融合结构,用于加强模型的特征提取和复用能力;同时在干扰区域特征提取模块中侧重于保留最关键的区域边界特征。此外,本文还建立了SAR受RFI影响的图片数据集用于评估所提出网络的效果。对比实验的结果表明,本文所提出的网络评估结果优于其他现有方法,能够衡量SAR图像受RFI的影响程度,同时具有较高的准确性。展开更多
我国正在进行大口径单天线和阵列射电望远镜的建设和预研工作。为保障射电望远镜前期建设工作的开展,首先需要找到满足电磁环境要求的台址,本文使用搬移式电磁环境监测装备在广东省清远市阳山县杜步镇、水口镇等预选台址开展了电磁环境...我国正在进行大口径单天线和阵列射电望远镜的建设和预研工作。为保障射电望远镜前期建设工作的开展,首先需要找到满足电磁环境要求的台址,本文使用搬移式电磁环境监测装备在广东省清远市阳山县杜步镇、水口镇等预选台址开展了电磁环境监测,并对广州市白云区帽峰山开展对比测试,采用一种干扰阈值判断方法对电磁环境监测数据进行了分析。分析结果显示,位于清远市阳山县杜步镇附近的洼地射频干扰(radio frequency interference,RFI)数量少且强度弱,该洼地远离城市中心,经济活动少,周围群山环抱,具有良好的电磁隔离性,适合大口径单天线和阵列射电望远镜的建设。本文的数据分析结果可为大口径射电望远镜的选址提供依据。展开更多
文摘随着无线电技术的发展,射频干扰(radio frequency interference,RFI)对射电天文观测的影响越来越大,尤其是周期性RFI对天文观测的影响越来越显著。本文围绕宽带、高时间分辨率频谱数据,采用阈值计算、噪声通道过滤、快速傅里叶变换、周期计算、通道合并、来源分析和模板库建立等步骤,提出一种面向宽带频谱序列的周期RFI统计方法。将该方法应用于新疆天文台南山观测站26 m射电望远镜(Nan Shan 26 m Radio Telescope,NSRT)脉冲星观测终端数据,有效地检测并提取出了频谱序列中的周期性RFI,可为进一步电磁干扰缓解提供数据支撑。
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。
基金supported by the National Natural Science Foundation of China(Grant No.11790305)partially supported by the Specialized Research Fund for State Key Laboratories(Grant No.SYS-202002-04)。
文摘Radio frequency interference(RFI)will pollute the weak astronomical signals received by radio telescopes,which in return will seriously affect the time-domain astronomical observation and research.In this paper,we use a deep learning method to identify RFI in frequency spectrum data,and propose a neural network based on Unet that combines the principles of depthwise separable convolution and residual,named DSC Based Dual-Resunet.Compared with the existing Unet network,DSC Based Dual-Resunet performs better in terms of accuracy,F1 score,and MIoU,and is also better in terms of computation cost where the model size and parameter amount are 12.5%of Unet and the amount of computation is 38%of Unet.The experimental results show that the proposed network is a high-performance and lightweight network,and it is hopeful to be applied to RFI identification of radio telescopes on a large scale.
文摘Radio Frequency Interferences (RFI), such as strong Continuous Wave Interferences (CWI), can influence the Quality of Service (QoS) of communications, increasing the Bit Error Rate (BER) and decreasing the Signal-to-Noise Ratio (SNR) in any wireless transmission, including in a Digital Video Broadcasting (DVB-S2) receiver. Therefore, this paper presents an algorithm for detecting and mitigating a Multi-tone Continuous Wave Interference (MCWI) using a Multiple Adaptive Notch Filter (MANF), based on the lattice form structure. The Adaptive Notch Filter (ANF) is constructed using the second-order IIR NF. The approach consists in developing a robust low-complexity algorithm for removing unknown MCWI. The MANF model is a multistage model, with each stage consisting of two ANFs: the adaptive IIR notch filter <i>H</i><i><sub>l</sub></i>(<i>z</i>) and the adaptive IIR notch filter <i>H</i><i><sub>N</sub></i>(<i>z</i>), which can detect and mitigate CWI. In this model, the ANF is used for estimating the Jamming-to-Signal Ratio (JSR) and the frequency of the interference (<i>w(0)</i>) by using an LMS-based algorithm. The depth of the notch is then adjusted based on the estimation of the JSR. In contrast, the ANF <i>H</i><i><sub>N</sub></i>(<i>z</i>) is used to mitigate the CW interference. Simulation results show that the proposed ANF is an effective method for eliminating/reducing the effects of MCWI, and yields better system performance than full suppression (<i>k<sub>N</sub></i>=1) for low JSR values, and mostly the same performance for high JSR values. Moreover, the proposed can detect low and high JSR and track hopping frequency interference and provides better Bit error ratio (BER) performance compared to the case without an IIR notch filter.
基金supported by the National Basic Research Program of China(Grant No.2011CBA00106)the National Natural Science Foundation of China(Grant No.11074008)the Research Fund for the Doctoral Program of Higher Education,China(Grant No.20100001120006)
文摘We describe the fabrication of high performance YBa2Cu3O7-δ （YBCO） radio frequency （RF） superconducting quantum interference devices （SQUIDs）, which were prepared on 5 mm×5 mm LaAlO3 （LAO） substrates by employing stepedge junctions （SEJs） and in flip-chip configuration with 12 mm×12 mm resonators. The step in the substrate was produced by Ar ion etching with step angles ranging from 47° to 61°, which is steep enough to ensure the formation of grain boundaries （GBs） at the step edges. The YBCO film was deposited using the pulsed laser deposition （PLD） technique with a film thickness half of the height of the substrate step. The inductance of the SQUID washer was designed to be about 157 pH. Under these circumstances, high performance YBCO RF SQUIDs were successfully fabricated with a typical flux-voltage transfer ratio of 83 mV/φ0, a white flux noise of 29 μφ0/√Hz, and the magnetic field sensitivity as high as 80 fT/√Hz. These devices have been applied in magnetocardiography and geological surveys.
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.
文摘从海量的天文观测数据中快速搜寻罕见的快速射电暴(Fast Radio Burst,FRB)事件,干扰缓解是其中一项关键而具有挑战的工作.射频干扰(Radio Frequency Interference,RFI)会淹没真实的天文事件,还会导致搜寻管线输出大量的假阳性候选体.由于干扰来源及其种类的复杂性,目前并没有一种通用的方法可以解决这个问题.为了降低干扰对FRB观测搜寻的影响,分析和研究了南山26m射电望远镜L波段观测数据中的干扰情况,针对主要的窄带干扰和宽带干扰建立了3层次的干扰缓解处理流程,从而有效缓解了观测数据的干扰污染情况.将该流程嵌入到FRB色散动态谱搜寻(Dispersed Dynamic Spectra Search,DDSS)管线中,实验结果表明,搜寻管线的检测率和检测精度得到了进一步的提高.该方法为FRB观测数据干扰缓解处理提供了有价值的参考.
文摘来自人造卫星的信号是射电天文观测面临的主要射频干扰(radio frequency interference,RFI)之一,这些RFI会将天文信号掩埋,为天文信号的搜寻和分析带来困扰。为了缓减卫星对天文观测的影响,我们在之前的工作中为500 m口径球面射电望远镜(Five-hundred-meter Aperture Spherical radio Telescope,FAST)开发了卫星电磁干扰监测软件,主要包括卫星数据库、观测模块和监测模块。近年来随着多个巨型卫星星座的规划发射以及望远镜观测模式的增多,卫星对射电天文观测的影响更为复杂,已有的软件已经不能满足实际的需要。为此,本文在单个卫星干扰分析的基础上提出了卫星星座的干扰评估方法,并对已有监测软件进行了升级,升级后卫星数据库覆盖更多的在轨卫星及星座信息且能够自动化更新,观测模块能够支持更多种观测模式下的卫星过境预测和干扰评估。在实际天文观测中,通过接在FAST接收机上的频谱仪数据对软件的干扰预测结果进行了实验验证,结果证明升级后的软件能够在多种观测模式下预测可能威胁的卫星以及对应的过境时间,为望远镜观测规划的调整、卫星干扰的规避和接收系统的保护提供重要的支撑。
文摘由于射频信号的广泛存在,合成孔径雷达(Synthetic Aperture Radar,SAR)在成像的过程中容易受到各类射频干扰(Radio Frequency Interference,RFI)的影响,这会导致获得的SAR图像质量下降,从而对后续的信息提取和目标识别等过程产生很大的影响。因此,衡量SAR图像受射频干扰的影响程度就尤为重要。然而,现有评估方法的鲁棒性通常较低,并且在评估时未考虑SAR图像受RFI影响的区域大小,因此本文提出了干扰区域⁃强度特征提取与联合评估网络。所提出的网络包含两个模块,干扰强度特征提取模块用于提取输入SAR图像中的干扰强度信息,干扰区域特征提取模块则侧重于干扰区域大小与边界信息的获取。由于SAR图像的尺寸一般比较大,因此本文在干扰强度特征提取模块中采用了多级残差和多层特征融合结构,用于加强模型的特征提取和复用能力;同时在干扰区域特征提取模块中侧重于保留最关键的区域边界特征。此外,本文还建立了SAR受RFI影响的图片数据集用于评估所提出网络的效果。对比实验的结果表明,本文所提出的网络评估结果优于其他现有方法,能够衡量SAR图像受RFI的影响程度,同时具有较高的准确性。
文摘我国正在进行大口径单天线和阵列射电望远镜的建设和预研工作。为保障射电望远镜前期建设工作的开展,首先需要找到满足电磁环境要求的台址,本文使用搬移式电磁环境监测装备在广东省清远市阳山县杜步镇、水口镇等预选台址开展了电磁环境监测,并对广州市白云区帽峰山开展对比测试,采用一种干扰阈值判断方法对电磁环境监测数据进行了分析。分析结果显示,位于清远市阳山县杜步镇附近的洼地射频干扰(radio frequency interference,RFI)数量少且强度弱,该洼地远离城市中心,经济活动少,周围群山环抱,具有良好的电磁隔离性,适合大口径单天线和阵列射电望远镜的建设。本文的数据分析结果可为大口径射电望远镜的选址提供依据。
