A geometric stability criterion for discrete time systems

A new stability criterion for discrete time systems which is obtained purely from the geometry of stability domain in the canonical parameter space is presented. The stability criterion is simple and recursive in nature. The connection between the new stability criterion and the Schur-Cohn criterion is established, leading to a simple algorithm to find the root distribution with respect to the unit circle. The new stability criterion is shown to be valid for polynomials with complex coefficients as well. This contribution can be viewed as a geometrical interpretation of the existing stability tests.