SPICE implementation of nonuniform frequency-dependent transmission lines

A technique for obtaining equivalent circuits of nonuniform single transmission lines, with frequency-dependent parameters is presented. This technique is based on the Branin´s method of characteristics. Existing commercial CAD software packages, such as SPICE, can be used for this implementation. The starting point of the technique consists of finding the functional relations between the S parameters nonuniform transmission line and the characterization functions of the circuit model proposed which are input impedances -Z₁(s)- and the propagation functions -F₁₂(s), F₂₁(s)-. The circuits are synthesized using conventional network synthesis techniques. An examination of the validity of the model is carried out analyzing the distortion of a trapezoidal pulse as it propagates along a microstrip taper line