一种天波超视距雷达电离层相位污染的校正算法

A Correction Algorithm for Ionospheric Phase Contamination in Sky-Wave Over-the-Horizon Radar

时变电离层的相位污染使天波超视距雷达高频回波谱展宽,影响对舰船等低速目标的检测。针对长相干积累时回波谱受到电离层大幅度相位调制导致正负Bragg峰重叠的情况,提出一种联合小波变换和基于模型假设的校正方法(即WTM法)。该方法首先利用小波变换补偿回波相位,使得正负Bragg峰可以初步区分,然后利用基于功率比的自适应滑窗信号提取方法取出初步校正后的标校信号,最后在时域根据假设的模型对回波信号进行精确的相位污染校正。仿真结果表明,该方法对于电离层大幅度相位污染导致的高频回波谱正负Bragg峰重叠的情况具有明显的去污染效果,性能优于改进的MESA法。

The significant Doppler spread of over-the-horizon radar（OTHR）echoes induced by the timevariant phase modulation of ionosphere limits the detection performance for low-speed targets,such as ships.Considering the spreading and overlapping Bragg peaks caused by ionospheric phase contamination with large amplitude in long coherent integration time（CIT）,ajoint correction scheme based on wavelet transform and the method of hypothetical model is proposed in this paper.In the scheme,wavelet transform is firstly used to compensate the echo phase so that the positive and negative Bragg peaks can be roughly distinguished.Then an adaptive sliding window filter based on power ratio is applied to extract the calibration signal,and accurate phase contamination correction is carried out based on the hypothetical model in time domain.The simulation results show that the scheme is effective for the situation of the two Bragg peaks overlapping caused by ionospheric phase contamination with large amplitude,and has a better performance than the improved maximum entropy spectrum analysis（MESA）method.