Sensitivity and gain margin optimization problems for strictly proper plant

Sensitivity minimization and gain margin maximization problems for SISO plants are considered using the Nevanlinna-Pick interpolation technique for analytic functions from the unit disk to itself. If a plant has no infinite zeros, the optimal performance can be attained exactly. However, if a plant has infinite zeros, the optimal performance can be attained only asymptotically. A method of parametrization of the stabilizing proper compensator satisfying the prescribed performance is also presented