Correction of artifacts in turntable inverse synthetic aperture radar images

Inverse synthetic aperture radar (ISAR) imaging on a turntable-tower test range permits convenient generation of high resolution two- and three-dimensional images of radar targets under controlled conditions, typically for characterization of the radar cross section of targets or for testing SAR image processing and automatic target recognition algorithms. However, turntable ISAR images suffer geometric distortions and zero-Doppler clutter (ZDC) artifacts not found in airborne SAR images. In this paper, ISAR images formed at Georgia Tech's Electromagnetic Test Facility are used to demonstrate and compare selected members of one family of two-dimensional ISAR imaging algorithms, from a simple but distortion-prone 2D discrete Fourier transform (DFT) to a computationally-intensive matched filter solution. A simple algorithm for correcting range curvature using image domain resampling is described. We then demonstrate two signal processing techniques to suppress zero-Doppler clutter while minimizing effects on the target signature. The first removes ZDC components in the frequency domain, whereas the second performs cancellation in the image domain.