Comments on hybrid-polarity SAR architecture

Recent work on compact polarimetry is reviewed in the context of the fifty-year history of polarimetric diversity. One promising form of this genre is hybrid-polarity (CL-pol), in which a synthetic aperture radar (SAR) transmits circular polarization and receives on two orthogonal mutually-coherent linear polarizations. The CL-pol technique is compared and contrasted to alternative compact polarimetric schemes. Useful characteristics that are unique to the hybrid-polarity architecture are described, especially rotational invariance and polarimetric calibration.