Modeling range-only tracking in airborne ISAR and nonlinear filter

The main task of inverse synthetic aperture radar imaging is to use the echo data of some points that received from the scan lines during the observation periods to reconstruct the target images. However, since the target and airborne ISAR are all moving objects, some points may disappear from the radar antenna beams, which will affect imaging results. In order to improve image qualities, it is very important to track the target range by virtue of the collected information and accurately control the antennas of ISAR to face the target. Because of the relative motion between the radar and target, their relative distances are usually nonlinearly variable with time. In this paper, a nonlinear model of range-only system is constructed by using a method of chord length approximation, based on which, a particle filter algorithm is presented for real-time tracking to the relative range. Finally, a compare is made between the new algorithm and other filtering algorithms under the same system model. The simulation results show that the former have higher accuracy.