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Signature Analysis and Discrimination Method of Preceded Frequency-shift False Target
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摘要: 由于距离-多普勒耦合效应的存在，线性调频信号易受到转发移频干扰，利用该原理产生的导前假目标具有诸多与真实目标相似的特性，传统的前沿跟踪等手段难以剔除，对雷达威胁很大。该文在剖析移频导前假目标产生的基本原理基础上，分析了假目标的特性，指出了导致真假目标难以分辨的内在原理及现有方法的不足。同时针对干扰信号难以鉴别的难点，利用干扰信号不可避免的转发延迟，分析经过匹配滤波处理后估计获得的到达时间与其实际到达时间之间的差异，进而提出了一种对移频转发形成的导前假目标鉴别方法并分析了这种方法的性能。最后通过相应的仿真实验验证了该方法的有效性。Abstract: Due to the effect of range-Doppler coupling between the time delay and shifted frequency of an LFM waveform, LFM radar is particularly susceptible to shift frequency jamming. A new deceptive jamming method, the Preceded Frequency-shift False Target (PFFT), has a similar signature to real radar targets, which indicates that conventional ECCM, such as leading-edge tracking, could be invalid when countering it. In this paper, the basic principle of PFFT is introduced and its signatures analyzed. Then, a new method for discrimination between a preceded false target generated by Digital Radio Frequency Memory (DRFM) and a radar target is proposed. By comparing the echo arrival time at the radar receiver front end with that estimated after a matched filter, the new method can extract the frequency modulation jamming signature and make a correct judgment. Simulation results are presented to verify the validity of the proposed method.
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图 1 真假目标信号的频谱、多普勒普及其匹配输出
Figure 1. Spectrum, Doppler spectrum, and matched filtering of true and false targets
图 2 移频导前假目标鉴别方法流程框图
Figure 2. Diagram of preceded frequency-shift false target’s identification method
图 3 回波与参考信号的时域关系图
Figure 3. Diagram of time-domain relationship between echo and reference signal
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