On Fri, Feb 10, 2012 at 1:54 AM, Jesse Lackey w= rote: > Hi - thanks for the description. =A0This is very interesting. =A0Do you p= ut > power and ground parallel to each other on the same pcb side, or have > them follow each other on opposite sides of the pcb? =A0It sounds like > they run parallel with your description of connecting the decouple cap > then the chip. You can do that, and I have on occasion, but that pretty much limits you to the edges of the board since on two layers you can't route anything across that on either layer. It's more about having parallel paths with as small a loop area as practical. > > Do you have a pic showing this? =A0I want to make sure I understand the > "T" vs. the "V". Not easily. If you think of the capacitor footprint, then each pad would have two traces connecting it, one pair goes to the chip and the other pair goes to the source. There are (expensive) caps that implement this with a four pad design, called "X2Y" caps. I haven't needed them yet. > I'm doing a bluetooth LE design in the coming weeks, and if I can make > it on a 2-layer (vs. 4-layer reference design) it would be a big win. =A0= I > realize there's a lot more to successful RF than power routing and > decoupling caps, but it would certainly help. I am doing 2.4 G on FR4 double sided. Be aware, the antenna dims are critical to 0.1mm and tuning varies with any dielectric material up to about 0.5" away from the antenna, and the exact shape of your ground plane. Whether the antenna is on the PCB or not, a mistuned antenna may cause your third harmonic to be drastically higher than it should be. We've seen 30dB reduction in third harmonics by using a particular filter balun from Johansen, and by keeping the antenna well matched. A significant mismatch may also drastically reduce your transmit power, depending on whether or not the folds back its output power on mismatch. We took our original antenna design to Don DeGroot in Longmont CO, with samples of the plastics for the enclosure. He used a VNA to measure the antenna in and out of the enclosure, and his own rig to measure the plastics dielectic constant, then redesigned the antenna for the proper tuning in the case. Well worth the cost! http://www.linkedin.com/pub/dir/Don/Degroot If you're in trouble with RF, and he can't help you... You are really hosed= ! --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .