Aircraft altitude estimation method based on multi‐beam pitching sum and difference channels for SAR

Abstract

Synthetic aperture radar (SAR) can provide high-resolution two-dimensional radar images of the target area. The error of the altitude between aircraft and the target area causes geometrical distortion of the SAR ground image, which is unfavourable for scene matching and target recognition. Existing methods, such as radar altimeters, work in the case of vertical beam irradiation. However, the highly accurate aircraft altitude estimation for SAR (under oblique irradiation) is still a challenge. In this paper, an aircraft altitude estimation method based on multi-beam pitching sum and difference channels radar echoes is proposed. The pitching sum and difference channels angle measurement principle is used to achieve accurate beam centre distance estimation, and the cyclic multiple beams are used to realise the estimation of the grazing angle deviation. Therefore, this method can realise the accuracy estimation of the aircraft altitude under oblique beam irradiation conditions. Then, the effects of various error sources on the accuracy of altitude estimation are analysed. The results of simulation and real data verify the correctness of the analysis and the validity of the proposed method.