COMPUTATIONAL MODELS OF TRANSMISSION-LINES WITH SKIN EFFECTS AND DIELECTRIC LOSS

We present circuit models of a length of transmission line with skin e ffect and frequency-dependent dielectric loss, treating the ordinary R LGC line as a special case. The line is modeled as a characteristic tw o-port in which the characteristic impedance is approximated as the in put impedance of a lumped circuit and the propagation function is appr oximated as the transfer function of a second lumped circuit plus an i deal delay. A unified approach based on frequency matching is presente d to form the model. In the approximation, the skin effect is represen ted as the impedance of an RL ladder, and the complex dielectric param eter as the admittance of an RC ladder. A table of the rms error of th e approximation is derived from which the complexity of the model can be found for a desired accuracy. The model is guaranteed to be stable, and since it consists entirely of lumped circuit elements and ideal d elay lines and since the model parameters can be easily computed, it c an be incorporated as a subcircuit model in a general circuit simulato r, and the solution can be obtained by integrating the circuit equatio ns in the usual manner. No FFT or convolution is required.