Comments on “a comparative study of vector fitting and orthonormal vector fitting techniques for EMC applications”

Vector Fitting (VF) is a robust method for rational fitting of frequency responses in the frequency domain. It has been proposed to replace the basis functions of VF (partial fractions) with an orthonormal set, leading to Orthonormal VF (OVF). A comparison between the VF and OVF methods was presented in a recent paper, claiming that OVF gives superior performance over VF. In this paper, it is shown that comparable results are obtained for VF and OVF if one uses the recommended set of starting poles, an adequate solver, and a column-scaling of least-squares (LS) equations. The same datasets are used to illustrate the result of both methods.