Instantaneous Doppler frequency for squint SAR imaging

Abstract

Instantaneous Doppler frequency for squint SAR imaging has been found with Chirp Scaling Algorithm (CSA). Because the azimuth sample is not perpendicular to the range sample, the range signal must impact on the azimuth signal in the squint SAR data processing, and the different slant range targets have different Doppler frequencies. From the mathematical model of SAR echo signal, this paper carefully analyzes the instantaneous azimuth frequency, the instantaneous Doppler frequency component of the azimuth frequency and the impact of range chirp on azimuth frequency, which explains that Doppler frequency should be properly selected for correct SAR imaging in the squint SAR. The results of point target simulation experiments show that the way is reasonable for the squint SAR and can effectively complete range compression and azimuth focusing, and improve images’ quality.