SOME PROBLEMS ON IQC''S OF THE DISCRETE-TIME SYSTEM
离散时间系统下的积分二次约束方法的几个问题

The stability of the feedback interconnection in the discrete time case is studied in this paper. Using the integral quadratic constraints(IQC's) methods, some stability criteria are given, some necessary conditions are also discussed. These results are suitable for both time invariant and time varying discrete systems. As an application, a stability criterion for the absolute stability in the MIMO case is given. Finally, using a stronger definition of IQC, a necessary and sufficient condition for a class of feedback interconnection is given.