Echoes covariance modelling for SAR along-track interferometry

There has been increasing interest in synthetic aperture radars (SARs) equipped with an along-track linear array of receiving antennas. These systems, called multichannel SAR (M-SAR), allow Doppler and angular information to be decoupled by means of along-track interferometric processing. Both the derivation of optimum estimation algorithms for physical parameters of the observed surface, in remote sensing applications, and of clutter cancellation schemes, in moving target detection, require the definition of a model for the covariance of the space-time clutter echoes to take full advantage of this potentiality. Moreover a proper representation space for the resulting space-time model is required to adequately interpret the results. Both models and representations are available separately for single channel SAR, where the long observation time and the consequent non-linear phase history of the echoes are the main issues, and for multichannel systems, which assume, on the contrary, a short integration time and focus on the angular characteristics. Our aim is to build a closed form model for M-SAR echoes, which takes into account both non-linear phase modulation and angular position at the same time and to define a proper representation space for it. Even though simple to handle, the model should encode all the main characteristics of the scattering from the observed scene