We have two parallel signal lines above a ground plane or between ground planes in a printed circuit board. In the last trace in Figure 3a we see a very narrow spike injected into the left hand line shown in Figure 1. It immediately breaks up into two spikes. In buried lines, Figure 2, these travel at the same velocity, Figures 5 and 6. However, in surface lines, Figure 1, they separate out. Before they separate out, see energy in the green region, Figure 9 and enlarged here , energy and upside down energy, are both travelling in the same direction in the same region of space. This demonstrates the extraordinary versatility of space in accommodating energy.
Ivor Catt. 17 November 2013