Interferometric methods for three-dimensional target reconstruction with multipass circular SAR

The authors consider three-dimensional (3-D) target construction from SAR data collected on multiple complete circular apertures at different elevation angles. The 3-D resolution of circular SAR systems is constrained by two factors: the sparse sampling in elevation and the limited azimuthal persistence of the reflectors in the scene. Three-dimensional target reconstruction with multipass circular SAR data is further complicated by non-uniform elevation spacing in real flight paths and non-constant elevation angle throughout the circular passes. The authors first study parametric spectral estimation methods that extend standard IFSAR method of height estimation to apertures at more than two elevation angles. Next, they show that linear interpolation of the phase history data leads to unsatisfactory performance in 3-D reconstruction from non-uniformly sampled elevation passes. The authors then present a new sparsity regularised interpolation algorithm to preprocess non-uniform elevation samples to create a virtual uniformly spaced array. The authors illustrate the performance of the proposed method using data from EM simulations and data collected from a wideband X-band airborne sensor.