电离层色散效应对星载SAR成像的影响

Effects of ionospheric dispersion on spaceborne SAR imaging

SAR信号传播过程中受到电离层色散效应的影响,不同频率的信号传播速度会出现差异。对于宽带线性调频信号,色散效应导致SAR信号产生传播时延,引入附加的超前相位。通过时域仿真方法仿真并分析不同载频、不同带宽、不同电离层TEC值和不同方位分辨率条件下,电离层色散效应对SAR成像的影响。结果表明电离层色散效应造成SAR图像距离向偏移、旁瓣升高和脉冲展宽等问题。P波段和L波段受电离层色散效应影响较为明显。C波段和X波段高分辨率星载SAR,信号带宽载频比值较大时,电离层色散效应的影响导致成像质量下降。

In the process of SAR signal propagation, the velocities of signal propagating at different frequencies are different due to the ionospheric dispersion effect. For the LFM signal with wide bandwidth, the dispersion effect results in the propagation delay of SAR signal, leading to additional advanced phase. In this study, the effects of ionospheric dispersion on SAR imaging under different carrier frequencies, different bandwidths, and different ionospheric TEC values are simulated and analyzed by using the time-domain simulation method. The results show that the ionospheric dispersion effect causes the SAR image to be shifted in distance with the sidelobe increase and pulse broadening. The P-band and L-band are obviously affected by the ionospheric dispersion effect. For C-band and X-band high resolution spaceborne SAR, the ionospheric dispersion effect leads to the degradation of imaging quality when the signal bandwidth carrier ratio is large.