Re: [SI-LIST] : Microstrip losses

Dr. Edward P. Sayre (esayre@nesa.com)
Mon, 26 Jul 1999 12:33:00 -0400

D. C. Wrote:
>That makes sense if your paths are 60 mils wide. For those of us
>using 3-5 mil traces skin effect may play a larger part.

Even in that case, the linear frequency dependence of dielectric loss will
dominate the square root of the frequency of skin losses, so dielectric
losses are the problem much above 2 GHz or so.

ed sayre
============================================
At 07:50 AM 7/26/99 -0700, you wrote:
>"WAUGH,RAY (HP-SanJose,ex1)" wrote:
>>
>> Chris...
>>
>> Indeed, the dielectric losses dominate in embedded microstrip and in
>> stripline, just as they do in conventional microstrip.
>
>That makes sense if your paths are 60 mils wide. For those of us
>using 3-5 mil traces skin effect may play a larger part.
>
>> -----Original Message-----
>> From: Chris_Heard@ne.3com.com [mailto:Chris_Heard@ne.3com.com]
>> Sent: Monday, July 19, 1999 5:23 PM
>> To: si-list@silab.eng.sun.com
>> Subject: RE: [SI-LIST] : even-odd mode influence
>>
>> Ray,
>>
>> You mention that material dominates losses on microstrips, is this no
>> longer true with embedded microstrips? Is this statement true with
>> stripline constructions as well? I would expect it to be so.
>>
>> Thanks for sending such excellent information.
>>
>> Chris Heard
>> 3Com Corp
>>
>> "WAUGH,RAY (HP-SanJose,ex1)" <ray_waugh@am.exch.hp.com> on 07/19/99
>> 07:05:05 PM
>>
>> Please respond to si-list@silab.eng.sun.com
>>
>> Sent by: "WAUGH,RAY (HP-SanJose,ex1)" <ray_waugh@am.exch.hp.com>
>>
>> To: "'si-list @silab.eng.sun.com'" <si-list@silab.eng.sun.com>
>> cc: (Chris Heard/US/3Com)
>> Subject: RE: [SI-LIST] : even-odd mode influence
>>
>> Steve...
>> The measurements I made on FR4 (and three other lower cost materials) were
>> made on microstrip lines which were five to eight inches long. What we (my
>> colleague Dan Swanson and I) did find is that microstrip line losses are
>> dominated by losses in the dielectric (rather than in the copper
>> conductors). As a consequence, the loss tends to be a fixed number when
>> expressed as dB/wavelength. See the attached PDF file.
>> At 10 GHz, an 18 inch FR4 microstrip line is going to be a bit lossy.
>
>--
>D. C. Sessions
>dc.sessions@vlsi.com
>
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>

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