天地波雷达回波的直达波抑制

A Method on Direct Arrival Wave Suppression for High Frequency Hybrid Sky-surface Wave Radar

高频天地波雷达是一种天发地收的新体制雷达,其信号传播信道主要包括电离层反射传播信道和海面绕射传播信道。电离层反射造成信号相位污染以及多径效应,接收机所接收到的天波直达波会发生频移和展宽,其强度一般远高于海洋回波,受污染后的直达波将会覆盖部分回波信息,影响海洋回波/海面目标的提取。本文根据天地波雷达直达波特性,提出了基于距离域自适应滤波抑制天地波雷达中的直达波强干扰的方法。该方法选择只含有直达波或直达波旁瓣信号的邻近距离元,作为自适应对消器的输入信号,实现天地波雷达回波信号中直达波及其旁瓣信号的抑制。实测结果表明,该方法能够很好的对直达波进行抑制,有利于海洋回波/海面目标信息的提取。

High Frequency hybrid sky-surface wave radar is a new mode of radar system with sky wave transmitting and surface wave receiving,whose signal path is mainly composed of the ionosphere reflection propagation and the sea surface diffraction propagation.The modulation by perturbations of ionosphere will result in the frequency shift and band width in the electromagnetic wave and induce multi-path effect in radar signal.The direct arrival wave of the radar is usually decades dB stronger than the sea echoes in intensity,therefore the sea echoes are partly covered by the contaminated direct arrival wave which bring more difficulty to extract the sea echoes from radar signal.Considering the high correlation of the direct arrival wave in range domain in hybrid sky-wave radar,a method based on adaptive filtering in range dimension to suppress the strong direct arrival wave interference is developed in this article.Data of adjacent range cells containing the direct arrival wave or its side-lobes are chosen as the input of the adaptive canceler to achieve the suppression of the direct arrival wave or its side-lobes in radar echoes at each range bin.Results of the processing of radar measurements indicate that this method works to suppress the direct arrival wave echoes and improve significantly the signal-to-noise-ratio of sea echoes.