[SI-LIST] Re: Microstrip/Stripline
- From: <jose_moreira@xxxxxxxxxxx>
- To: <si-list@xxxxxxxxxxxxx>
- Date: Tue, 13 Dec 2005 20:25:59 +0100
Hi,
On this discussion between microstrip and striplines I do not see any =
reference to the fact that a microstrip is in fact not surounded by air =
but it does have a plating surface and probably solder mask on top of =
that and on the sides.
At designCon 2006 there will be an article showing some of the =
difference between microstrips with different plating techniques (Si, =
NiAU, etc..) and striplines. There is a difference and for test and =
measurement this difference can be significant if you have long trace =
lengths.
The microstrips were 21mils wide in Rogers4350 and the striplines were =
19mils also in Rogers.
Best Regards
Jose Moreira
_____________________________________________________
Jose Moreira
Senior Application Consultant
STS Center of Expertise
Agilent Technologies R&D and Marketing GmbH & Co.KG
Herrenberger Strasse 130
CCST-BUS
D-71034 Boeblingen
Germany
Phone: +49-7031/464-6493
Fax: +49-7031/464-4708
Email: jose_moreira@xxxxxxxxxxx
______________________________________________________
=20
=20
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] =
On Behalf Of Chauhan, Prakash
Sent: Dienstag, 13. Dezember 2005 20:19
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Microstrip/Stripline
In the defense of Microstrip Topologies, I would offer the =
following:=3D20
For a given impedance and the same signal to plane spacing, the width of =
the microstrip should be roughly twice what it would be for a stripline.
So the skin effect loss should be approximately the same. The resistive =
loss will be lower as the cross section is twice that of the stripline =
and the dielectric loss should be lower as well. If the signal could be =
routed entirely on the outer layer with no vias, it would surely be =
better for signal quality. Also microstrips offer faster propagation =
delays so they can be used to improve timing margin on busses. =3D20
--Prakash.=3D20
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Lee Ritchey
Sent: Tuesday, December 13, 2005 12:04 PM
To: Hassan O. Ali; babid_a@xxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Microstrip/Stripline
The higher skin effect loss for the same width microstrip transmission =
line over the same width stripline is more likely due to the fact that =
most of the current in the microstripline is confined to the side of the =
trace exst to the plane over which it runs while the stripline trace has =
current distributed over both sides. The under side of a surface =
microstripline is roughened in order to make it bond to the prepreg =
layer, increasing the loss.
This is offset, somwhat, by the fact that a surface microstripline has =
air on one side which has a lower loss tangent that the dielectrics of =
the stripline version.
As someone pointed out, there isn't a simple answer to this question. I =
rarely use surface microstriplines because the impedance control on =
outer layers is so poor, so this question doesn't come up.=3D20
Lee W. Ritchey
Speeding Edge
P. O. Box 2194
Glen Ellen, CA 95442
Phone- 707-568-3983
FAX- 707-568-3504
I just used the energy it took to be angry to write some blues.
Count Basie
> [Original Message]
> From: Hassan O. Ali <hassan@xxxxxxxx>
> To: <babid_a@xxxxxxxxx>; <si-list@xxxxxxxxxxxxx>
> Date: 12/12/2005 10:45:38 PM
> Subject: [SI-LIST] Re: Microstrip/Stripline
>
> Babid,
>
> You can always find a microstrip line that is more lossy than a
stripline. You can also=3D20
> find a stripline that is more lossy than a microstrip line. =
You'll=3D20=20
> have
to fix some=3D20
> parameters of interest and then ask the same question.
>
> For example, you can fix the trace width, trace thickness, dielectric
constant, electric=3D20
> loss tangent, metal conductivity, and characteristic impedance =
for=3D20=20
> both
line types=3D20
> (allowing the trace height to vary to give rise to the required
characteristic=3D20
> impedance). You may also need to specify whether or not the=20
> stripline=3D20 is
symmetric, i.e.=3D20
> the center strip is the same distance from the two reference=20
> planes.=3D20 You
should also fix=3D20
> a frequency band of interest - low frequency loss behavior can be
different from high=3D20
> frequency loss behavior.
>
> In general though, a microstrip is more lossy than a stripline. The
fundamental reason is=3D20
> that a stripline provides two planes through which the return currents
could pass, hence=3D20
> less resistive loss (two resistors in parallel). But at higher
frequencies where=3D20
> dielectric loss dominates over skin-effect (resistive) loss, the story
can be different.=3D20
> That's pretty much material-dependent.
>
> Now go find a book if you need more info.
>
> Best regards.
>
> Hassan.=3D20
>
>
>
> On Dec 12, "Tom Dagostino" <tom@xxxxxxxxxxxxx> wrote:
> >=3D20
> > There are many good books that describe this. I would suggest=20
> >you=3D20 try
the
> > "Transmission Line Design Handbook" by Brian C. Wadell as a good
source.
> >=3D20
> > Tom Dagostino
> > Teraspeed(R) Labs
> > 13610 SW Harness Lane
> > Beaverton, OR 97008
> > 503-430-1065
> > tom@xxxxxxxxxxxxx
> > www.teraspeed.com
> >=3D20
> > Teraspeed Consulting Group LLC
> > 121 North River Drive
> > Narragansett, RI 02882
> > 401-284-1827
> >=3D20
> > -----Original Message-----
> > From: si-list-bounce@xxxxxxxxxxxxx
> > [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Babid A
> > Sent: Monday, December 12, 2005 5:44 PM
> > To: si-list@xxxxxxxxxxxxx
> > Subject: [SI-LIST] Microstrip/Stripline =3D20 =3D20 Which is more =
lossy=20
> >between microstrip and stripline? why?
> >=3D20
> > Thanks,
> > -Babid
> >=3D20
>
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