Synchronization for mini-UAV-based high-resolution BiSAR systems: Lost direct signal estimation based on Hampel filtering

In mini-unmanned aerial vehicle-based high-resolution bistatic synthetic aperture radar systems, the rotation of the unmanned aerial vehicle platforms will cause direct signal loss, resulting in the reduction of synchronization error compensation accuracy. Here, a synchronization algorithm is proposed to estimate the lost direct signal. First, bistatic time and phase synchronization signal models are established. Then, Hampel filtering is used to estimate the time delay of the lost direct signal, and the time and phase synchronization errors are estimated based on third-order polynomial fitting. A high-resolution synthetic aperture radar image is used to demonstrate the validity of the proposed algorithm in mini-unmanned aerial vehicle-based high-resolution bistatic synthetic aperture radar systems.