An improved PGA algorithm for ionosphere phase perturbation correction

Ionosphere phase perturbation destroys the coherence of echo signal for sky-wave Over-The-Horizon Radar (OTHR) and broadens the spectrum of signal and clutter, which will exacerbate the property of low-speed object detection. PGA (Phase Gradient Autofocus) is an excellent perturbation correction algorithm with properties of logical, concise, robust etc for various perturbations. In particularly, it will reduce computation work enormously. However, the estimate accuracy of PGA is degraded when the Bragg peak filter bandwidth is selected improperly, or the zero frequency components are not acquired exactly, then the iteration times should be increased. An improved PGA is proposed for ionosphere phase perturbation correction, which can realize adaptive selection of the first order clutter filter bandwidth. At the same time, a method of zero frequency abstraction based on Bragg frequencies symmetry is presented, which can decrease iteration times with same perturbation function estimate accuracy and higher computation efficiency.