Improving the pole relocating properties of vector fitting

This paper describes a modification of the vector fitting (VF) procedure for rational function approximation of frequency domain responses. The modification greatly improves the ability of VF to relocate poles to better positions, thereby improving its convergence performance and reducing the importance of the initial pole set specification. This is achieved by removing the high frequency asymptotic requirement of the scaling function used by VF. Calculated results demonstrate a major improvement of performance when fitting responses that are contaminated with noise. The procedure is also shown to be advantageous for transmission line modeling and wide band transformer modeling