Rational functions play a central role in the analysis of the dynamics of electric power systems. One of the most used methods to synthesize rational functions of power system elements and sub-networks in frequency domain is Vector Fitting (VF). This paper presents the Matrix Pencil Method (MPM) of the time domain as a viable alternative to rational synthesis. A modification of MPM is proposed in this paper. The two methods, VF and MPM, are compared and applied in the rational synthesis of the transfer (propagation) function of a transmission line.