Multi-look coherent synthetic aperture radar (SAR)

The interference between two radar images, acquired from approximately the same location, has a number of uses. In particular, the literature abounds with examples of coherent change detection (CCD) and interferometric SAR (InSAR) uses which respectively enable the detection of small changes and the extraction of terrain elevation. In almost all of these examples, coherent estimates have been formed by spatially averaging the interfered images to obtain reliable estimates. This paper looks instead at averaging independent looks that, although more complicated, allow higher resolution coherent products to be formed over larger areas by reducing the constraints on the allowable quadratic phase error that typically limits image size.