Analysis of Moving Target Identification (MTI) Algorithms for Airborne SAR

Abstract

In the frame of the ARGOS project a near-real time onboard processor for Ground Moving Target Identification (GMTI) should be developed for the F-SAR system. The objective of the work is to develop a fast moving target position and motion parameter estimation procedure. Since after common SAR focusing the moving targets become displaced in azimuth and range, by measuring the offset it is possible to estimate their motion parameters as well as their true beam center positions. The offset measurement requires, however, a priori knowledge, i.e. the exact road position within the SAR image. The innovation of the presented work is mainly the pre-processing step: SAR focusing and dual-channel calibration is quickened by selecting only relevant parts of the range compressed data – namely a few patches that cover all the roads of interest in the dataset. Besides no further adaptive focusing for each target is necessary, as the algorithm relies just in the detected target position at the commonly focused SAR data. In addition, the target velocity estimation (both across- and along-track components) makes use not only of the azimuth displacement to the road, but also of the often disregarded range shift. Furthermore, as the commonly focused signal is still too smeared for an accurate displacement measurement, a refinement in the Doppler domain is employed to get a sharper detection and hence a more accurate motion parameter estimation. The algorithm description comprehends mainly the coordinate transformation - latitude/longitude to range/azimuth – and an iterative procedure for accurate displacement and velocity estimation. The implemented program output is both the target motion parameters and the "true" geographic coordinates. The whole procedure has been verified with real FSAR data.