A Novel Method For Non-planar Target Imaging With DSM

In case of circular or non-linear acquisition trajectory, synthetic aperture radar (SAR) focusing becomes increasingly sensitive to elevation. For non-planar target imaging, it not only appears fore-shortening along range but also blurred along azimuth. As the wider integration angle and higher elevation of objects, the defocus cannot be ignored. Generally, the polar format algorithm (PFA) is an efficient imaging algorithm for circular or non-linear SAR. However, in the process of PFA, the impact of focusing at an inexact altitude is not be considered. In this article, the conventional PFA is adapted to incorporate the known digital surface model (DSM) into the imaging process. Firstly, the maximum allowable elevation deviation (MAED) δz<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</inf> is derived. Secondly, for non-planar target that higher than δz<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</inf> , applying data extraction in range-Doppler domain and multiplying compensation function that constructed based on DSM data separately. The corresponding original echo data is then replaced with the processed data. The whole method only involves fast Fourier transform (FFT) and complex multiplication which makes it better operational efficiency. The experimental data results demonstrated the effectiveness and practicability of the proposed algorithm.