15th Triennial World Congress of the International Federation of Automatic Control
  Barcelona, 21–26 July 2002 
PHASE CONDITIONS FOR SCHUR POLYNOMIALS
L.H. Keel* S.P. Bhattacharyya**
* Center of Excellence in Information Systems
Tennessee State University
Nashville, TN 37203-3401, USA
** Department of Electrical Engineering
Texas A&M University
College Station, TX 77843, USA

The rate of change of phase of a real or complex Schur polynomial, evaluated along the unit circle traversed counterclockwise is strictly positive. For polynomials with real coefficients this bound can be tightened. These and some other fundamental bounds on the rate of change of phase are derived here using the Tchebyshev representation of the image of a real polynomial evaluated on the unit circle.
Keywords: Phase condition, Schur stability, Tchebyshev representation
Session slot T-We-A15: Robust Analysis II/Area code 2e : Robust Control