Ways to determine approximate magnitude of crosstalk between PCB layers

Question

Is there any basic methods to calculate crosstalk between different layers in a multilayer PCB. I am not after anything exact just a way to grasp the magnitude of the issue.

The situation I am trying to solve is in a 4 layer space constrained PCB with a stackup of Signal-Ground-Power-Signal, on my bottom layer I have a number of differential +/- 10V Signals max freq 1KHz. On the power layer above these traces I have a power trace with a current varying between 0-200mA with a minimum rise time of approximately 0.1ms, the trace for the return current is directly adjacent.

Assuming there is no other way I can route my PCB how can I go about getting a feel for what kind of affect a step in my current can affect my signals.

Other data

Signal Output impedance <100 ohms

• Signal Input impedance approx 10k ohms
• Signal trace width 12mil, trace separation 12mil
• Power trace width 40mil, separation 20mill
• Copper Weight 1oz
• Outer plane separation 0.2mm
• Inner plane separation 1.2mm
• Length of parallel run 75mm

Answer 1

As @derstrom8 suggested, there are better tools for doing this, but tend to be expensive & aimed at pros. I vaguely remember there is a FOSS field-solver tool out there somewhere, but can't remember. But if I interpret your PCB stack-up figures correctly, you may be able to approximate your situation with the Saturn tool I mentioned:

If you set it to 'stripline' mode where you're calculating crosstalk of 2 tracks sandwiched within 2 planes, and then set the distance of the bottom plane effectively to infinity (500mm) because that doesn't exist in this scenario, then set H1 to the gap between your 2 inner planes (where the lower plane is your power track on the inner-bottom, right?), and H2 to the gap between bottom-layer & bottom-plane (what you describe sounds like a typical 4-layer stack-up), I see -84dB, or 1.25mV.

Perhaps with that rough idea you can use your input-impedance & knowledge of the broader system to work out how significant this may or may not be.