On Jan 23, 2008 10:54 AM, alan smith wrote: > I've got a square board, but with a circle routed out in the middle. Its about 200mm square, with a 100mm diameter circle. > > So, I'm thinking that its probably not a really good idea to have it be a solid ground plane, but for EMI purposes somwhere it should slice that plane so its not a complete loop and act as an antenna. > > Thoughts? It depends.. (standard EMI answer :) If you have a lot of high speed current flowing, then it will go around the circle, but then again, the root problem would be that you don't have the source and return currents taking the same path, or as close to it as possible. If you do, then having the plane go all the way around should be fine, as you wouldn't have current using the plane to find it's way home. -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist