电离层频率调制导致地表面杂波的多谱勒展宽,极大地限制了高频天波雷达的目标探测性能.本文针对这种电离层频率调制,给出了一种级联的两步校正处理的方法.在第一步校正中,首先分析这种时变信号的时频分布,并设计了一种谱峰追踪方法从时频分布中获得粗糙的电离层频率调制估计.然后采用基于分段多项式相位模型的参数化方法作二次校正处理,消除残余调制污染.模拟结果表明,即使对Bragg峰发生混叠的重污染的情形,这种级联的校正方法都具有非常好的效果.%Ionospheric frequency modulation causes spreading of the surface clutter in Doppler domain which greatly limits the detection performance of HF sky-wave radars. This paper proposes a cascaded approach to correct the ionospheric frequency modulation. This approach consists of two correction steps. At the first step, time-frequency distribution (spectrogram or pseudo Wigner-Ville distribution) of the time-varying signal is adopted and a peak-tracking scheme is designed, to obtain a coarse ionosperic modulation estimation from the time-frequency distribution. At the second correction step, a parametric method based on piecewise polynomial phase model is exploited to eliminate the residual contamination. Simulation results show the effectiveness of this cascaded approach even for very serious cases where broadened Bragg lines are overlapped.
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