Detecting overlap of switching windows between coupling nets is a major static technique to accurately locate crosstalk noise. However, due to the mutual dependency between switching windows, the computation requires iterations to converge. In this research, we discuss the issues and provide answers to the important questions involved in convergence and numerical properties, including the effect of coupling models, multiple convergence points, convergence rate, computational complexity, non-monotonicity, continuity, and the effectiveness of bounds. Numerical fixed-point computation results are used to explain these properties. Our contribution here builds a theoretical foundation for static crosstalk noise analysis .