An ISAR imaging algorithm for multiple targets of different radial velocity

Inverse Synthetic Aperture Radar (ISAR) is a well-known technique for acquiring images of a moving target by using the synthetic aperture method. This radar improves the angle resolution based on the Doppler effect accompanying the relative motion with respect to the target, estimates the target motion from the echoes, and must compensate for the range migration during the observation and the fluctuations in the Doppler frequency. However, the problem faced when multiple targets, such as a formation of airplanes, are simultaneously observed is that the echoes of targets having slightly different motions interfere and degrade the estimation of the motion and the image resolution. Here, we propose an algorithm capable of separating the echo of each target, estimating the motion of each target, and compensating for the unwanted motion of each target based on the motion estimates even when multiple targets are simultaneously observed by utilizing the two-dimensional discrete Fourier transform. We conducted computer simulations and demonstrated the ability to generate the images from two target echoes and confirmed the effectiveness of the proposed method. (C) 2003 Wiley Periodicals, Inc.