Diagonal loaded array interpolation methods for multibaseline cross-track SAR interferometry

This work deals with the problem of interferometric radar phase (IP) estimation in the presence of multiple height layover components. The focus here is on multibaseline interferometric synthetic aperture radar (InSAR) systems with a low number of phase centres and nonuniform array geometry. Interpolated array (IA) approaches allow the application of parametric spatial spectral estimation techniques designed for uniform linear arrays (ULAs). The need for obtaining a well conditioned IA transformation matrix results in the estimation of a virtual ULA output with a number of elements lower than or equal to that of the actual non uniform linear array (NLA). Here we extend the IA approach to allow a greater number of virtual elements by means of a diagonal loading (DL) technique. The simulated performance of the proposed technique is compared with that obtained by means of another interpolation algorithm, that is optimal in a mean square error (MSE) sense, and with the Cramér-Rao lower bound (CRLB) calculated for the NLA.