Abstract: 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.

Key words: ionosphere, dispersion effect, spaceborne synthetic aperture radar, phase advance