Rotor blades blockage modulation suppression algorithm for helicopter-borne SAR

There exists periodic modulation problem in radar echoes due to the main rotor blades periodic blockage in helicopter-borne fire-control radar which is mounted atop the main rotor mast of the helicopter. Such modulation echo induces a set of ghosts in synthetic aperture radar (SAR) image, further resulting in a poor performance of subsequent tracking and striking. To address this problem, this article proposes a method on rotor blades blockage modulation suppression for helicopter-borne SAR. By decomposing the blocked echo into the form of Fourier series in the azimuth direction, a reference function could be constructed to suppress the modulation directly by adopting an iterative approximation strategy. This method effectively avoids the complex blocked data recovery methods, and thus can be used to suppress various kinds of periodic modulation components without requiring certain distribution models. Both simulated and real-measured data are processed to demonstrate the effectiveness of the proposed algorithm.