P波段雷达成像电离层效应的地面观测与校正

Ground Observation and Correction of P-band Radar Imaging Ionospheric Effects

对于高分辨率星载P波段SAR系统,电离层效应对P波段SAR会带来一系列较为严重的误差,这些误差与电波频率和电离层积分电子总量(TEC)值关系密切,并使得图像质量下降。为了获得高质量的图像,必须对电离层误差进行校正。该文基于电离层导致的匹配滤波失配的数学模型,指出获得准确的电离层TEC是校正的关键,提出了一种高精度的基于SAR回波相位反演电离层TEC的测量方法,并利用地基P波段雷达对空间目标进行穿透电离层步进频ISAR观测验证,实测数据处理结果表明,该方法有效提高了电离层TEC测量精度,改善了ISAR成像质量,可适于低频段星载SAR系统的电离层效应测量与校正应用。

For high resolution space-borne P-band SAR system, ionospheric effects could cause serious phase errors. These errors are causally related to the radar frequency and the TEC of ionosphere and make the image quality degraded. To guarantee the image quality, the ionosphere errors must be emended. Based on the mismatched filter model caused by ionosphere, it is pointed out that accurate ionosphere TEC is the key for phase error correction, a high precision ionosphere TEC measurement method is further put forward by using the phase errors of SAR echoes, which is validated by processing the data of a ground based P-band radar with well focused radar image of the international space station obtained. The results indicate that the method can effectively increase the accuracy of ionosphere TEC estimation, and thus improve the radar imaging quality, it is applicable to low frequency space-borne SAR systems for reducing the ionosphere effects.