Rational approximation of frequency responses via singular value decomposition

This paper describes a non-iterative method for rational approximation of frequency-domain responses based on application of the Singular Value Decomposition algorithm. Using causality, a system response measured for positive frequencies is extended to negative frequency range. Impulse response is directly available through known inverse Fourier transform of a rational approximation in the partial fraction expansion form. The method is demonstrated using an example with known Fourier transform pair, as well as a practical example, where measured frequency response of a power transformer has been used.