This paper considers the problem of identifying regions in the complex-plane, such that the phase of polynomials having roots in those regions, is bounded by that of a few extreme polynomials. Applications of the results are also described.
Proceedings of the 33rd IEEE Conference on Decision and Control
Convergence, Telecommunication standards, robust control
Abdallah, Chaouki T. and F. Perez. "Phase-convex arcs in root space and their application to robust SPR problem." Proceedings of the 33rd IEEE Conference on Decision and Control (1994): 3729-3730. doi:10.1109/CDC.1994.411737.