On the two block problem for unstable distributed systems

The H/sub infinity / mixed sensitivity minimization problem is solved for a class of unstable distributed systems. The solution is based on an extension of the skew Toeplitz methodology. The key mathematical fact used is that the skew Toeplitz operators arising in the unstable case are finite rank perturbations of the classical skew Toeplitz operators obtained from compressions of rational functions. A simple example is used to illustrate the theory developed here.