Parameter identification of transfer functions using an improved vector fitting method

The paper presents an improved vector fitting method for the approximation of the non-flat amplitude-frequency response curve of an antenna used in near-field measurements. The method introduces a first order derivative and a post-multiplication of the coefficient matrix by a diagonal matrix to the standard vector fitting method. Simulation and application results showed that the improved methodology can approximate the finer details of the actual frequency response curve better. It also produces a higher fitting accuracy when compared to the general vector fitting method. The improved method also has the advantage of requiring a smaller sample size in the frequency domain.