Eliminating redundant DC equations for asymptotic waveform evaluation

Asymptotic waveform evaluation (AWE) is a waveform estimation technique which involves the computation of moments from a linear circuit followed by the generation of waveform estimates based on those moments. During moment computation a special case arises if there are capacitor cutsets or inductor loops. Methods proposed for handling these cases involve identifying the cutsets and loops and replacing one of the capacitors (inductors) with a dependent source. This note describes a different formulation of the problem. The elimination of redundant equations in order to compute moments can be viewed as the dual of the problem of reducing circuit equations to normal form. This formulation has a couple of interesting theoretical properties: (1) it formally handles all circuit topologies, including circuits with dependent sources for which the redundancies may be undetectable from an inspection of the circuit topology; and (2) it predicts that even networks without independent sources may have “hidden” particular solutions consisting of polynomials in t