Compensation of Space-borne SAR Imaging Degradation Due to the Ionospheric Scintillation

The altitude of low earth orbit (LEO) SAR systems is generally 200-1000 km. Thus, compared with the area of the ionosphere, the SAR signals inevitably pass through the ionosphere twice and degrade the quality of SAR imaging. This will affect the performance and applications of space-borne SAR at low frequencies, e.g., object recognition and classification. Earlier theoretical analysis and experiments show that the main effects of ionosphere is due to the ionospheric scintillation, which can cause randomly fluctuations in azimuth phase history and serious defocus will be happened. Hence, it is crucial to put forward the mitigation technique before designing the space-borne SAR systems. By using the phase gradient autofocus (PGA) method, we attempt to compensate the ionosphere-polluted SAR imaging in this paper. Numerical simulation results show that the image quality after PGA can be improved significantly.