SAMPLED-DATA SIMULATION OF PERIODICALLY SWITCHED NONLINEAR CIRCUITS - Computer Methods for Analysis of Mixed-Mode Switching Circuits - page 152

At the switching instants, the two-step algorithm is applied to ob-
tain the consistent initial conditions of sensitivity networks. Assume a
switching occurs at In the forward step, the sensitivity of the
Volterra circuits at is calculated using (7.36) and (7.37). In
the backward step, we calculate the sensitivity of the Volterra circuits
at is obtained by differentiating (7.32) and (7.33) with respect

to

and

Finally, the sensitivity immediately after switching is obtained by
summing up that of all Volterra circuits