Estimation and Compensation of the Ionosphere Effect in SAR Imaging

In the aspect of the transmitting error compensation in SAR imaging, the research of the ionospheric effect on the radar echo is developed. As the random and dispersive nature of the ionosphere, it will severely affect the propagation and scattering of electromagnetic waves through it, especially in the spaceborne earth observation SAR and the ground-based space observation ISAR. The ionosphere model is constructed and the ionospheric effects are analyzed first. And then the way to evaluate the total electron content (TEC) from the received ISAR signal is explored based on the ionospheric contaminated phase. Finally, two estimation methods are proposed to compensate the ionospheric effect on SAR and ISAR signals: one is the method to estimate the TEC in the frequency domain, which can be applied to the spaceborne SAR and the ground-based ISAR. The other is the technique to estimate the TEC by the two-dimensional spectrum division, which is validated by the real experiment data from a ground-based ISAR;Furthermore, an estimation method based on minimum entropy principle is analyzed as well.