SAR ambiguities in skewed antenna arrays

It is well known that the area of a synthetic aperture radar (SAR) antenna must exceed a minimum value to avoid image ambiguities. The classic minimum ambiguity-free area criterion was derived for rectangular antennas that are aligned with the direction of travel and are rolled to the look angle. This paper derives an analogous criterion that is valid for nadir-facing, yawed, and non-rectangular antenna geometries. The resulting maximum beam area criterion (MAXBAC) includes the classic result as a special case for rectangular antennas of conventional orientation. It is shown theoretically, and verified numerically for representative examples, that using an unconventional antenna geometry does not improve main beam ambiguity performance.