This chapter has not been about how to use a particular simulator the vendors provide extensive literature and classes to cover that. Rather, this chapter has presumed that you are already familiar with the basic tools but need information as to how those tools can be applied to digital interconnect design at microwave frequencies. I wouldn't expect you to be able to smoothly transition to ever higher frequencies without aid. This chapter addressed various issues that you may never have seen unless you spent time talking to microwave engineers. Sure, eventually we would all have heard of slot lines and patch antennae, but here is a leg up. Many of the subjects introduced here are also covered in tomes of mathematics and theory. This book should not be the final look you take at many of these subjects. On the other hand, not everyone has the time to read a dozen microwave books to discover the source of that peculiar resonance on the new circuit board.