Continued-fraction model-reduction technique for multivariable systems

The method of obtaining a reduced-order state variable model, by truncating the continued-fraction expansion of a matrix polynomial, is considered. It is shown that the method has several limitations, e.g. the number of inputs must equal the number of outputs, and that it is possible for the denominator of the reduced model to be of a higher order than the given system. It is shown that the full expansion does not exist in many cases. It is concluded that the method is very restricted.