1. A method for characterizing linear properties of an electrical component having n>1 ports, which linear properties are described in a matrix Y relating a voltage applied to the ports to a current through the ports, wherein a frequency dependence of Y is approximated by Y ⁡ ( s ) ≅ Y rat ⁢ ⁡ ( s ) = ∑ m ⁢ R m s - a m + D + sE wherein the subscript “rat” denotes a rational function, m runs from 1 to a number N of poles, R m with m=1 to N are frequency independent matrices, D and E are frequency independent matrices or zero, s denotes a complex angular frequency iω, and a m with m=1 to N are complex angular frequencies of the poles, said method comprising: a) obtaining a set of values Y(s) of Y at discrete frequencies s, and, for each value Y(s), obtaining eigenvalues λ i and eigenvectors t i with i=1 to n; b) fitting, in a processor of a computer processing device, a set of n vector equations λ i  λ i  ⁢ ( ∑ m = 1 N ⁢ r ~ m s - a m + 1 ) ︷ σ ⁡ ( s ) ⁢ t i ≅ 1  λ i  ⁢ ( ( ∑ m = 1 N ⁢ R m s - a m + D + sE ) · t i ) to the eigenvalues λ i and eigenvectors t i , wherein {tilde over (r)} m is a frequency-independent scalar with m=1 to N, by using a first set of pole frequencies am and by varying {tilde over (r)} m , R m and, if assumed to be non-zero, D and E; c) calculating, in the processor of the computer processing device, a second set of pole frequencies from: 
 { a m }=eig( A−b·c T ) wherein A is a diagonal matrix holding the first set of pole frequencies am as diagonal elements, b is a vector of ones, c is a vector holding {tilde over (r)} m for m=1 to N as obtained by step b), and eig is an operator returning a vector holding eigenvalues of a matrix; d) repeating steps b) and c) by using the second set of pole frequencies am of step c) as the first set of pole frequencies in a subsequent step b) until a stop condition is met; and e) outputting a model approximating the linear properties of the electrical component in which the applied voltage is related to output currents in the electrical component.