Motion-Based Separation and Imaging of Closely Spaced Extended Targets

Separating images of multiple moving extended-targets by means of ultra-wideband (UWB) frequency-modulated-continuous-wave (FMCW) radar is investigated. The difference in motion of closely-spaced extended targets is used to separate and image them when their radar signatures overlap in the range-azimuth domain. A novel auto-focusing criterion based on the entropy of the eigenspectrum and the Fourier spectrum is proposed for target imaging using inverse synthetic aperture radar (ISAR). It allows separating closely spaced targets and estimating their motion parameters. The criterion proposed overcomes the low Doppler resolution of closely-spaced extended targets of conventional techniques. The bearing information is extracted by signal reconstruction for every target separately. With the estimated position and the motion parameters of multiple targets, their images are reconstructed using standard imaging processing algorithms. The performance of the proposed method is validated via numerical simulations.