Within many well-established theories for robustness study, the structured singular value (SSV), briefly called /spl mu/, has been proven a powerful tool for robust stability and robust performance criteria. Several /spl mu/ values and the related properties have been developed for different uncertainty models. In the paper, we address issues related to phase /spl mu/ when, in the blocking diagonal-structured uncertainty, each repeated scalar uncertainty contains phase information bounded by a symmetric cone. An algorithm is developed and implemented for the computation. Finally, a numerical result is given to show the obtained lower bound for different phase constraints.