A simple method for deriving J-spectral factors

A simple method is presented for deriving the J-spectral factor of a transfer function matrix explicitly in terms of the parameters of this matrix. This method provides closed-form expressions for the J-spectral factor and its inverse which only require a solution of a single linear Sylvester equation. This method can be easily applied in the solution of the H/sub infinity /-optimal regulation problem, and it provides useful geometric insight into the structure of the optimal regulator return difference matrix.<
>