On J‐Lossless coprime factorizations and H^∞ control

This paper presents a relatively simple approach, based on chain scattering descriptions, to the synthesis of internally stabilizing controllers which result in a cost function with H^∞ norm strictly less than a prespecified bound. State‐space formulae for a generator of all suboptimal controllers are found by solving two coupled J‐lossless coprime factorizations of a chain scattering matrix description. A mixed‐sensitivity design problem is used to illustrate the solution procedure, and to demonstrate how in certain cases only one algebraic Riccati equation need be solved to get a solution.