Upper bounds for mixed H/sup 2//H/sup /spl infin// control

We consider the mixed H/sup 2//H/sup /spl infin// control problem of choosing a controller to minimize the H/sup 2/ norm of a given closed-loop map, subject to the H/sup /spl infin// norm of another closed-loop map being less than a prescribed value /spl gamma/. Let d/sub 2/ and /spl gamma//sub 2/ denote the H/sup 2/ and H/sup /spl infin// norms for the pure H/sup 2/-optimal solution (without any H/sup /spl infin// constraint), and let d/sub c/ and /spl gamma//sub c/