Re: [SI-LIST] : Stripline VS. Microstrip losses

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From: Yaping Zhou (y.zhou@motorola.com)
Date: Tue Apr 24 2001 - 14:52:11 PDT


Jason:

My two cents.

1) If the center conductor is thick enough (>~ 5x skin depth), copper loss
in stripline could be roughly half of that in microstrip.You can think of
the current distribution in the two structures .

2) I agree that dielectric loss in microstrip is less. How much less depends
on the width/height ratio, which determines the magnitude of the fringing
field.

3) Conductor loss in microstrip or stripline is always dominant if a low
loss dielectric material is used. It's easy to get high Q ( low loss)
dielectric materials (e.g. Alumina ), while conductor loss is difficult to
decrease (This's the reason why a lot people are studying superconducting
materials to fabricate low loss microstrip line to make narrow band
filters). Therefore, I'd definitely choose stripline to decrease the total
loss since stripline has less conductor loss.

Yaping Zhou

Motorola Semiconductor Products Sector

----- Original Message -----
From: "Pritchard, Jason" <jasonp@tenornetworks.com>
To: <si-list@silab.eng.sun.com>
Sent: Monday, April 23, 2001 4:27 PM
Subject: [SI-LIST] : Stripline VS. Microstrip losses

If I have 2 transmission lines, 1 embedded in stripline with equal spacing
between the signal conductor and both planes and the other in microstrip.

1) How much does the proximity effect increase the copper losses/skin effect
in microstrip vs. that of stripline?

2) I presume the dielectric losses are less in microstrip. If that is true,
is there a point where it cancels out the negative effects of question 1?

3) Which do you prefer when trying to decrease copper and dielectric losses
and why?

Thanks,
Jason Pritchard

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