An Intuitive Approach to Fit A frequency Dependent Equivalent Circuit for Transmission Line Models

Accurately fitting rational functions to the frequency response of characteristic impedance and characteristic admittance is very crucial for frequency dependent modeling of transmission lines. Vector fitting is a most popular method for fitting rational functions to the frequency dependent characteristic impedance of transmission line. An R-C equivalent circuit will then be obtained from rational functions to simulate transmission line using Marti's model. An intuitive single step method is proposed in this paper to directly fit an equivalent circuit to the characteristic impedance. A close enough fitting is achieved with lesser number of poles & zeros using the proposed method. This is found to reduce the simulation time drastically by 89.84%.