Transmission Line Models for Use with Circuit/System Analysis Programs

Techniques for modeling multiconductor transmission lines for use with the SCEPTRE computer program are presented. The transmission line models developed can be modified for compatibility with other circuit/ system transient analysis programs and are amenable to modification to include nuclear weapon effects. The general modeling approach has been to develop computationally efficient and accurate terminal models which can be arbitrarily loaded at the source and load ends and which can be used in conjunction with nonlinear electronic circuit models using either simplified or discrete modeling techniques. The concept of the method is to derive a set of transfer functions in the Laplace domain relating forward and backward traveling waves on the line to voltages and currents at the source and load ends of the line, approximate the transfer functions with a set of orthonormal polynomials, and represent the resulting rational polynomials in the time domain with state variable differential equations. For the multiconductor case, the orthogonal characteristics of wave propagation are used to decouple the modes of propagation except at the source and load boundary condition circuits.