AAA Algorithm for Rational Transfer Function Approximation With Stable Poles

Signal and power integrity analysis in time-domain requires suitable models for interconnects and power distribution networks, which are often available only in terms of their frequency responses from electromagnetic simulations or measured data. A rational transfer function approximation of such data allows its integration in circuit simulators. Recently the AAA (adaptive Antoulas-Anderson) algorithm has been introduced for rational function approximation. This letter introduces a modification of that algorithm for fitting in terms of the squared variable ( s
²
), called AAA
²
algorithm, for generating rational transfer functions with stable poles from frequency response available from simulated or measured data.