[SI-LIST] : FW: signal isolation, RF board

Anthony Tse (anthony.tse@nrl.navy.mil)
Fri, 30 Jan 1998 12:28:38 -0500

Hello all,
I am in the process of designing a RF board (160MHz) and I need to =
isolate a low level inputs from the output of a high gain amplifier. I =
re-read all the article in the archive on guard-banding and shielding =
and didn't really get a good feel on how to go about doing this. Here =
are some questions:
Realistically, how much isolation can I get? The traces in question are =
about 2" long and 4" apart.
The stacking is 2 & 4 ground, layer 3 for RF signal, and layer 1 for =
video signal. Since there are very few traces on layer 3, should I =
solder pour the whole layer and stitch the 3 ground planes together =
around all the sensitive signal traces? Or am I better of using fat =
guard traces and stitch them to the ground plane.
Does it make sense to separate the two signals in two different layers? =
Say one of the signals in layer 2 with 1 & 3 as the ground while the =
other signal is in layer 3 with 2 & 4 as ground. Or should I bit the =
bullet and go to a 6 layer board, with 1,3,4,6 as ground and 2 & 5 as =
signal (50 ohm trace width may be a problem with a 6 layer board).
Are there any good book/article/web site on this topic??
Thanks.
-Anthony