A real-time self-focusing method for sar based on direct estimation of phase error

Abstract

The invention discloses an SAR real time self-focusing method based on phase error direct estimate, belonging to the radar imaging technology field. The method comprises the steps as follows: selecting strongest scattering point of each distance unit below the PGA algorithm processing structure, removing the strongest scattering point of each distance unit to the centre of the distance unit, adding window for the image of each distance unit, obtaining the fixed phase difference value between the remaining distance unit and the reference distance unit, eliminating the fixed phase difference value from each distance unit, having weighted average on the distance unit signal after eliminating the fixed phase difference value to obtain the phase error function, and compensating the phase error function. The phase error function is directly estimated after executing the unbiased estimation on the fixed phase difference for reducing the iterative times, reducing operation number, obviously improving focusing quality, the method is applied to the SAR image with long-scale contrast and without stronger target.

Description

technical field [0001] The invention discloses a SAR real-time self-focusing method based on phase error direct estimation, and belongs to the technical field of radar imaging. Background technique [0002] Synthetic aperture radar (SAR) has the capability of high-resolution imaging under all-weather and all-weather conditions. Since SAR is a coherent imaging system, there is a close relationship between the SAR image and the phase of the received signal. The inevitable various approximations in the SAR imaging algorithm, as well as the deviation of the aircraft from the ideal track, speed and flight attitude during the actual flight, will cause a large phase error of the received signal, which will lead to the deterioration of the image focus quality. Significantly decreased. Especially in high-resolution imaging systems, the image defocusing phenomenon caused by the non-ideal motion of the antenna is more serious because of the longer aperture time required. Even if an ...

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Problems solved by technology

[0004] The technical problem to be solved by the present invention is to aim at the deficiency of the above-mentioned background technology, provide a SAR real-time self-focusing method based on the direct estimation of the phase error, adopt the processing structure of the PGA algorithm, and estimate the fixed phase between each distance unit based on the SAR image signal model The difference value, combined with the estimation operator that directly estimates the phase error function, realizes the self-focusing processing of the SAR image, so as to improve the defect that the PGA algorithm estimates the first derivative of the phase error function because of the low estimation accuracy caused by the accumulation of noise.

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