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| Figure 6. Measuring the inductively coupled noise on the victim trace adjacent to the aggressor signal with no gap and separated by a gap. The inductively coupled noise is reduced by about 40% on the victim trace separated by a gap. This is a small impact. |
The following is excerpted from Professor Eric Bogatin's article in the Signal Integrity Journal, The Case for Split Ground Planes. Reprinted by permission of Signal Integrity Journal.
This section continues from the discussion on Return Current at Low Frequency.
. . .
Inductively Coupled Noise
In a plane, at frequencies below about 10 kHz, return currents will not flow under the signal path, but will spread out in the return plane. Above 10 kHz, the return currents are localized under the signal paths.
When we have two adjacent signal paths that are over a wide, continuous plane, they will show inductive cross talk at high frequency. Even with minimal overlap of the return currents, there is still loop mutual inductance between the two signal-return paths. This inductive noise is driven by the changing current, the dI/dt, in the aggressor signal-return path, which will get smaller at lower frequency.
