antenna-theory.com

[Nanoantenna]

We're investigating skin effect in some wires, but our results are very sporadic. What we find is that the skin effect, which in turn affects the resistance, does not decrease linearly (on a log scale) as it should. It demonstrates some linear characteristics in the 10-200 MHz range, but below this range, the resistance decreases slightly, where it should be increasing. Above the 200 MHz range, the graphs become horribly erratic, showing seemingly no pattern at all, with a spike at 560 MHz. What contributes to this inconsistency in resistance at the lower frequencies and 200+ frequencies? Any help would be greatly appreciated (especially from you, Schubert and Big Steve )

[bigSteve]

Schubert's on travel. But here are my thoughts.

Remember that skin depth theory is based on the current decreasing exponentially away from the surface. So for your lower frequency range, I'd imagine that the decrease is not fast enough (relative to the thickness of your wire). So basically the decrease won't show up because there isn't enough space for the current to die off in the diameter of the wire.

Above the 200 MHz range, I imagine you have some sort of measurement error, or you are measuring series inductance or possibly even some radiation resistance if your wire is a resonant length. It's tough to say without seeing a detailed picture of what is going on and doing some hands on debugging.

Anyway, that's my thoughts.