Blind-velocity SAR/ISAR imaging and detection of moving targets

The first part of this dissertation presents a SAR/ISAR coherent system model and inversion to image a target moving with an unknown constant velocity in a stationary background. The approach is based on a recently developed system modeling and inversion principle for SAR/ISAR imaging that utilizes the spatial Fourier decomposition of SAR data in the synthetic aperture domain to convert the SAR system model's non-linear phase functions into linear phase functions suitable for a computationally-manageable inversion. It is shown that SAR/ISAR imaging of a moving target can be converted into imaging the target in a stationary squint-mode SAR problem where the parameters of the squint-mode geometry depend on the target's velocity. A method for estimating the moving target's velocity that utilizes a spatial Doppler analysis of the SAR data within overlapping subapertures is presented. Unlike the temporal Doppler processing methods used to estimate a moving target's velocity, the spatial Doppler technique does not require the radar signal to be narrowband. Thus, the reconstructed image's resolution is not sacrificed to improve the target's velocity estimator.; In the second part, the detection and reconstruction problems are considered where targets under the heavy clutter are moving with unknown velocities within the ISAR footprint. Two detection methods that are manageable in regard to computation time are presented. One method is based on incoherent processing where the magnitude of the returned signals obtained at different temporal frequencies are incoherently added in the spatial frequency domain. The other method uses coherent processing techniques such as Fourier transform to localize the target's signal signature. After detecting the moving target via coherent processing, target's signal signature is retrieved by filtering. Subaperture processing method introduced in the first part is applied to the retrieved target's echo for estimating target velocity and finally reconstructing the target.