Application of Fractional Fourier Transform to Moving Target Indication via Along-Track Interferometry

A relatively unknown yet powerful technique, the so-called fractional Fourier transform (FrFT), is applied to SAR along-track interferometry (SAR-ATI) in order to estimate moving target parameters. By mapping a target’s signal onto a fractional Fourier axis, the FrFT permits a constant-velocity target to be focused in the fractional Fourier domain thereby affording orders of magnitude improvement in SCR. Moving target velocity and position parameters are derived and expressed in terms of an optimum fractional angle α and a measured fractional Fourier position up, allowing a target to be accurately repositioned and its velocity components computed without actually forming an SAR image. The new estimation algorithm is compared with the matched filter bank approach, showing some of the advantages of the FrFT method. The proposed technique is applied to the data acquired by the two-aperture CV580 airborne radar system configured in its along-track mode. Results show that the method is effective in estimating target velocity and position parameters.