EFFICIENT CIRCUIT SIMULATION OF NONUNIFORM TRANSMISSION-LINES

This paper extends the transmission-line simulation method of [1] to n onuniform lines. The method is applicable to multiconductor lossy freq uency-dependent transmission lines characterized by sampled frequency- domain responses. The resulting model can he directly incorporated int o a circuit simulator. The implementation includes ac, de, and transie nt analyses. The method is reliable, accurate, and as efficient as the simple replacement of interconnects by lumped resistors. The method i s based on approximation, and its accuracy and efficiency result from the simplicity of characteristic responses. To apply the method to non uniform lines, two novel nonuniform line models are introduced. An ope n-loop model completely separates forward and backward waves and resul ts in the simplest aperiodic responses, but does not guarantee their s tability. An open-loop distributed-reflection model explicitly include s the internal distributed reflections, and provides the simplest stab le characterization. It is shown that for nonuniform lines, the genera lized method of characteristics no longer separates forward and backwa rd waves. Numerical example of a parabolically tapered frequency-depen dent four-conductor line is given.