On circularity/noncircularity in single-channel synthetic aperture radar imagery

Motivated by the conventional resolution theory, phase content in single-channel synthetic aperture radar (SAR) imagery is often discarded. In this paper, the validity of this practice is studied from the perspective of complex-valued statistics. Hence, for the phase content to be irrelevant, the complex-valued random variable has to be second-order circular. A procedure to characterize circularity/noncircularity in single-channel SAR imagery is presented. Our analysis is applied to real-world SAR chips from Radarsat-2 and MSTAR. For the case of extended targets, the complex-valued SAR chip is found to be inherently noncircular. Further, the strength of noncircularity is observed to be resolution-dependent. Also, a proportional relationship between noncircularity and nonlinearity is noted. These findings warrant investigating the statistical significance of this phenomenon in relevant target recognition applications.