H-infinity control problem for general discrete-time systems

— This paper considers the H∞ control problem for a general discrete–time system, possibly improper or polynomial. The parametrization of suboptimal H∞ output feedback controllers is presented in a realization–based setting, and it is given in terms of two descriptor Riccati equations. Moreover, the solution features the same elegant simplicity of the proper case. An interesting numerical example is also included.