Abstract— This paper proposes a novel approach to L2sensitivity minimization problem of state-space digital filters subject to L2-scaling constraints. The proposed approach reduces the constrained optimization problem to an unconstrained optimization problem by appropriate variable transformation. As a result, iterative algorithms for the L2-sensitivity minimization without L2-scaling constraints can be applied to the L2-sensitivity minimization subject to L2-scaling constraints. Our novel approach can achieve the L2-sensitivity minimization with quite faster convergence behavior.