Generalized frequency weighted balanced reduction

A generalization of frequency weighted balanced reduction is worked out that comprises D. Enns´ (1984) original frequency weighted balanced reduction and an extension of the frequency interval balanced reduction of W. Gawronski and J.N. Juang (1990). In this extension, scalar quadratic frequency functions can be assigned in separate frequency intervals. Weighting in frequency points is also developed. This generalization provides a very direct and flexible way of specifying frequency weightings. In a MATLAB implementation, the frequency weightings can be adjusted and refined until the reduction error (after weighted balanced reduction) is satisfactory. This is shown in an example