[SI-LIST] Re: GND is perfect conductor?
- From: "McCoy, Bart O." <McCoy.Bart@xxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Thu, 4 Sep 2003 14:12:04 -0500
>> We routinely assume perfect conductors for ground in our field solvers.
>> In fact, I don't believe you have an option of doing otherwise for ADS
>> (I've got a request in for information on this, but can't get a reply
>> until next week).
ADS has a whole variety of microstrip models to choose from.
Their "Multilayer" models, rather than being equation based,
use a 2D field solver on arbitrary geometries you specify.
When specifying those geometries, you can just make all metal lines on
various layers to be "signals" and simply put small microstrip "signal"
lines over top of larger "signal" lines. Tie the larger "signal" lines
to ground and that becomes your microstrip ground. Tie the other
"signal" lines to your source and load and they are your microstrip.
According to their help file online, skin-effect is accounted for and I know
for sure that signal line conductivity can be specified.
That's the beauty of field solvers-- you don't have to have implicit
grounds--- a ground is just another signal line. The impedances
will come out as expected when wide, high-conductivity grounds are
used. Microstrip losses seem to compare favorabily (within 10% or so) to
some
hardware I just evaluated and compared to my multi-layer ADS models.
- Bart
-----Original Message-----
From: Loyer, Jeff [mailto:jeff.loyer@xxxxxxxxx]
Sent: Thursday, September 04, 2003 12:28 PM
To: Signal Integrity Mailing List
Subject: [SI-LIST] GND is perfect conductor?
We routinely assume perfect conductors for ground in our field solvers.
In fact, I don't believe you have an option of doing otherwise for ADS
(I've got a request in for information on this, but can't get a reply
until next week). And, for XFX, I don't know whether it comprehends any
skin effects of the Ground plane (it says it applies the default rho
for resistivity, but I don't know what that does for an infinitely wide
conductor). Ansoft Q2D, on the other hand, allows setting the
characteristics of the ground plane (since it's just another conductor).
I would expect that, at current (>5GHz) frequencies, the ground plane
losses would have a significant effect (the current in the ground plane
would be a mirror image of that in the signal conductor), including skin
effects. The Hall, Hall, McCall book even gives a formula for the
effect (page 80). But, our simulators don't seem to take it into
account.
1) Does anyone have any information (data would be preferred, vs.
conjecture) on the effects of using a perfect vs. imperfect conductor
for ground?
2) If ground plane losses don't have any effect, why don't they?
3) If ground plane losses do have an effect, how do you properly model
them in XFX and/or ADS?
Jeff Loyer=20
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List archives are viewable at:
//www.freelists.org/archives/si-list
or at our remote archives:
http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List archives are viewable at:
//www.freelists.org/archives/si-list
or at our remote archives:
http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
Other related posts:
