International audienceThis paper deals with observer-based stabilization for a class of Linear Parameter-Varying (LPV) systems in discrete-time case. A new LMI design method is proposed to design the observer-based controller gains. The main contribution consists in providing a new and convenient way to use the congruence principle to reduce the conservatism of some existing results in the literature. This use of congruence principle leads to some additional slack matrices as decision variables, which make disappear some bilinear terms. To the authors' best knowledge, this is the first time the congruence principle is exploited in this way. The effectiveness and superiority of the proposed design techniques, compared to existing results in ...