<title>Polarimetric subspace target detector for SAR data based on the Huynen dihedral model</title>

Two new ,polarimetric subspace target detectors are developed ,based on a ,dihedral signal model ,for bright peaks within a spatially extended target signature. The first is a coherent dihedral target detector based on the ,exact Huynen model for a dihedral. The second is a noncoherent dihedral target detector based on the Huynen model with an extra unknown,phase term. Expressions for these polarimetric subspace target detectors are developed for both additive Gaussian clutter and more general additive spherically invariant random,vector (SIRV) clutter including the K-distribution. For the case of Gaussian clutter with unknown clutter parameters, constant false alarm rate (CFAR) implementations of these polarimetric subspace target detectors are developed. The performance,of these dihedral detectors is demonstrated,with real millimeter-wave fully polarimetric SAR data. The coherent dihedral detector which is developed with a more,accurate description of a dihedral offers no performance advantage over the noncoherent dihedral detector which is computationally more attractive. The dihedral detectors do a better job of separating a set of tactical military targets from natural clutter compared,to a detector that assumes no knowledge,about the polarimetric structure of the target signal.