The key to narrow-band interference excision in frequency domain is to determine the excision thresh- old in direct-sequence spread-spectrum (DS-SS) systems. The excision threshold is a non-linear function related t...The key to narrow-band interference excision in frequency domain is to determine the excision thresh- old in direct-sequence spread-spectrum (DS-SS) systems. The excision threshold is a non-linear function related to the number and the power of interference, and attempting to get the exact relation of threshold related to the number and the power of interference is almost impossible. The N-sigma algorithm determines the excision threshold using subsection function; however, the excision threshold determined by this method is not exact. A new method to determine the threshold of N-sigma algorithm is proposed. The new method modifies the scale factor N by use of the membership function. The threshold determined by this method is consecutive and smooth, and it is closer to the fact than that of the initial N-sigma algorithm. The GPS signal and single-tone (CW) interference (that is, typical narrow-band interference) are implemented in the simulation, and the results are presented to demonstrate the validity of the new algorithm.展开更多
面对日益复杂的空间电磁环境,合成孔径雷达(Synthetic Aperture Radar,SAR)容易受到射频干扰(Radio Frequency Interference,RFI)的影响,从而严重影响图像的判读和解译。尤其是低波段(例如P波段)SAR系统,由于频段内存在大量的电视广播信...面对日益复杂的空间电磁环境,合成孔径雷达(Synthetic Aperture Radar,SAR)容易受到射频干扰(Radio Frequency Interference,RFI)的影响,从而严重影响图像的判读和解译。尤其是低波段(例如P波段)SAR系统,由于频段内存在大量的电视广播信号,更容易受到RFI的影响。在建立了射频干扰信号模型的基础上,根据RFI信号的高功率、窄频带特点,提出了一种基于联合滤波的RFI抑制方法。该方法结合了传统的陷波法和子空间投影法在SAR射频干扰抑制方面的优点。其基本思想是:首先利用子空间投影法,将回波投影到目标信号子空间,获得参考信号,根据该参考信号,利用3δ准则判别出回波中存在的干扰信号,进行陷波、赋值处理。这样既降低了子空间投影法在抑制干扰过程中由于信号子空间判断误差而引入的虚警,又为陷波处理提供更准确的判别门限和更优的权值,可有效提升干扰抑制效果。仿真结果验证了该方法的干扰抑制效果优于子空间投影法及传统频域陷波法。展开更多
文摘The key to narrow-band interference excision in frequency domain is to determine the excision thresh- old in direct-sequence spread-spectrum (DS-SS) systems. The excision threshold is a non-linear function related to the number and the power of interference, and attempting to get the exact relation of threshold related to the number and the power of interference is almost impossible. The N-sigma algorithm determines the excision threshold using subsection function; however, the excision threshold determined by this method is not exact. A new method to determine the threshold of N-sigma algorithm is proposed. The new method modifies the scale factor N by use of the membership function. The threshold determined by this method is consecutive and smooth, and it is closer to the fact than that of the initial N-sigma algorithm. The GPS signal and single-tone (CW) interference (that is, typical narrow-band interference) are implemented in the simulation, and the results are presented to demonstrate the validity of the new algorithm.
文摘面对日益复杂的空间电磁环境,合成孔径雷达(Synthetic Aperture Radar,SAR)容易受到射频干扰(Radio Frequency Interference,RFI)的影响,从而严重影响图像的判读和解译。尤其是低波段(例如P波段)SAR系统,由于频段内存在大量的电视广播信号,更容易受到RFI的影响。在建立了射频干扰信号模型的基础上,根据RFI信号的高功率、窄频带特点,提出了一种基于联合滤波的RFI抑制方法。该方法结合了传统的陷波法和子空间投影法在SAR射频干扰抑制方面的优点。其基本思想是:首先利用子空间投影法,将回波投影到目标信号子空间,获得参考信号,根据该参考信号,利用3δ准则判别出回波中存在的干扰信号,进行陷波、赋值处理。这样既降低了子空间投影法在抑制干扰过程中由于信号子空间判断误差而引入的虚警,又为陷波处理提供更准确的判别门限和更优的权值,可有效提升干扰抑制效果。仿真结果验证了该方法的干扰抑制效果优于子空间投影法及传统频域陷波法。