abid wrote, "I don't know how to implement the SDD component in Figure 5"
This might not answer your question, but a first-look suggests that the "SDD" component might be the circuit in Figure 3.? After saying that, now I will back-track and suggest an alternative.? Both circuits appear to have these components in common: Lp, Rs, Cp.? If these are indeed the same elements with the same values in both figures, then it suggests that the "SDD" component represents only these parts of Figure 3: Cr, Rf, Cf, Vo, and the switch.? The switch might be key to making it model the step-recovery diode.? That is only a guess on my part.
Note that both circuits also appear (exactly the same) in Fig. 1 of the IEEExplore article that started this discussion.? Note the big red arrow in that figure, suggesting that parts (a) and (b) might be the same as one another.
Andy
