Progress in radar imaging for maneuvering targets

Abstract

Radar imaging is an essential technique to acquire fine structural characteristics of a target. For a maneuvering target, however, the resolution of the traditional range-Doppler-based inverse synthetic-aperture radar (ISAR) imaging decreases on both the range and azimuth directions. Along the range direction, the resolution is determined by the bandwidth of the radar, which is limited by the hardware of the radar system. In addition, the high velocity of the target can result in a stretch of the range profile, thus decreasing the resolution. Along the azimuth direction, the complex target motion produces a time-varying nonlinear Doppler frequency, which destroys the imaging conditions for ISAR and causes a reduction of the resolution. In this paper, the effects of the target complex motion on ISAR imaging are firstly presented. The process of ISAR imaging for maneuvering targets is then elaborated from the dimensions of the range and Doppler. In this regard, high-velocity compensation, multiband fusion imaging, high-order phase-error compensation, and sparse ISAR imaging are mainly presented. Several techniques of radar imaging for maneuvering targets, which could overcome some shortcomings of ISAR imaging, are then discussed, including the wave front modulation and electromagnetic vortex imaging. Finally, the current works on radar imaging for maneuvering targets are summarized, and future perspectives are discussed.