[Errata]

The equation on p. 40 of the August 2011 issue of IEEE Microwave Magazine in the article “Essential Principles of Signal Integrity” [1] was incorrect. The correct equation should read: $\delta {\rm{ = }}\sqrt {{1 \over {\sigma \pi \mu _0 \mu f}}} = 2.1\mu \sqrt {{1 \over f}}.$ We apologize for any confusion this may have caused.