Copyright: 1996 - 2024
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Wire spacing and other PCB stuff - RF Cafe Forums
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Below are the old forum threads, including responses to the original posts.
|-- Amateur Radio
Gripes & Humor
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Post subject: Wire spacing and other PCB stuff Posted:
Tue Jan 31, 2006 9:47 am
I understand that the
width of a piece of wire (PCB track) depends on how much current is
going through it. In dealing with high frequency signals, what is the
rule for spacing wires apart?
If I had a DC pin next to a AC
(high frequency) pin on an IC, do I need to route the wires away from
each other? Also, in this type of setup, would a capacitor from the
DC to GND alwasy be recommended?
Also, I've noticed that some
high frequency circuits have copper planes on the top and the bottom.
Is there a specific reasoning for this? Are these mostly ground planes?
Post subject: Posted: Sat
Feb 18, 2006 3:35 pm
Joined: Mon Jun 27,
2005 2:02 pm
Hello Guess Who,
If I had a DC pin next to a AC (high frequency) pin on
an IC, do I need to route the wires away from each other? Also, in this
type of setup, would a capacitor from the DC to GND alwasy be recommended?
Yes you should route the high-frequency signals away
from the DC signals to prevent coupling between them. Capacitors of
several values are always needed to bypass voltage supplies. They should
be placed as close as possible to the voltage supply pins.
Also, I've noticed that some high frequency circuits have copper planes
on the top and the bottom. Is there a specific reasoning for this? Are
these mostly ground planes?
Yes these copper planes are
usually GND planes. In RF PCB layout there is great importance to form
a continuous GND plane. Therefore; where no signals are passing the
area is covered with GND. I suppose that you have also noticed that
GND planes exist on both sides of RF traces (microstrip lines). This
type of transmission line is called Coplanar.