Reduction of polarization parameters of measured coherency matrix by unitary transformations

In this paper, four unitary transformations based on coherency matrix have been proposed, which are ellipticity angle transformation, quasi-ellipticity angle transformation,, absolute phase transformation and quasi-absolute phase transformation. These four proposed unitary transformations can eliminate [T₁₃], Re[T₁₃], Im[T₁₂] and Re[T₁₂], respectively. With the supplement of the proposed four decomposition methods, there exist six angle rotation methods that can be selected to eliminate the corresponding six non-diagonal elements of the coherency matrix. It has also been found that element T₃₃ is reduced after the rotation of ellipticity angle and quasi-ellipticity angle. Therefore, these two corresponding unitary transformations can be used in polarimetric decomposition theorem to discriminate urban blocks and vegetation. Taking ellipticity angle transformation as an example, the results of the experiment confirmed the characteristics of the proposed unitary transformations.