A High-Frequency Multipeak Model for Wide-Angle SAR Imagery

A new modeling method for representing distributed scattering centers in wide-angle synthetic aperture radar (SAR) is presented. The proposed multipeak model approximates amplitudes of localized image peaks that typically appear at a single pixel or as an in-line set of pixels in a SAR image. In this way, the multipeak model is an improvement over existing peak models which poorly represent distributed canonical scatterers, such as the common dihedral with a fold line oriented parallel to the imaging plane. The model is derived from a wide-angle approximation of the well-known attributed scattering center or parametric models when under the action of a linear imaging operator. It is shown that, under typical imaging conditions of 10
$^{ \circ}$
or more in the synthetic aperture, the multipeak model approximates the image peak amplitudes due to distributed canonical scatterers as if they are due to an equivalent point scatterer with an azimuth-independent dispersive amplitude function in the spectral domain. This improves parameter estimation and scatterer classification, and it is also shown that the imaging relative error due to the approximation is less than 2% for other common image processing conditions such as tapered windowing in azimuth and when the canonical scatterer is at least ten wavelengths in size. A distinct advantage of the multipeak model over point scatterer models is that parameter estimation and scatterer classification can be performed solely in the spatial domain on a pixel-by-pixel basis and efficiently integrated within a linear SAR imaging process. To illustrate the benefits and limitations of the approach, parameter estimation and scatterer classification experiments are presented using simulated SAR data.