A frequency synchronization method for hybrid bistaitc SAR using direct path signal

We propose a frequency synchronization method for hybrid bi-static synthetic aperture radar (SAR), which denotes a SAR system with a spaceborne illuminator and an airborne receiver. Due to the high altitude difference, the method based on extracting the direct path signal is employed. The mathematical model to compute the frequency offset between the two sides´ oscillators is given. Among the model, a novel method for estimating the Doppler centroid for hybrid bi-static SAR is proposed. Error analysis is carried out, and the result indicates that under normal signal to noise ratio and frequency stability level the estimation error is within the acceptable value. A simulation was performed and the result shows that the imaging result is favorable after compensation.