A steady-state add-on to the algorithm for implicit numerical integration

Many software tools of the PSpice class do not contain an implementation of the steady-state algorithm, especially for autonomous circuits. In the paper, an add-on is described to the algorithm for implicit numerical integration which determines the steady state of both nonautonomous and autonomous circuits by an extrapolation method. The extrapolation procedure is based on scalar epsilon-algorithm which is relatively easy for programing and efficient in terms of number of required iterations. Since the selected algorithm for the implicit numerical integration gives values of derivatives at any time, the determination of unknown periods of autonomous circuits can be performed by modified Newton-Raphson method. The efficiency of the procedure is demonstrated by the steady-state analysis of a tunable distributed microwave oscillator with the results compared with measured data.