[SI-LIST] : PCB losses

Mike Degerstrom (degerstrom.michael@mayo.edu)
Tue, 20 Jul 1999 08:42:50 -0500

Ray,

Hope you don't mind but I changed the subject line as we
are drifting far from the "even-odd" mode thread.

Thanks for sharing your data with us. It looks as though
you would expect around 2dB loss at 10Ghz for your 91mm
cyanate ester microstrip. This would indicate that >10Gb/s
operation with relatively long pcb traces is feasible (although
it would take a very good package and package-to-board interface).

One item that you omitted was the cross sections of the conductors.
>From what I can gather is that your cross sections are 1/2 oz.
copper and conductor widths of at least 60 mils wide on a
.81mm (32 mil) thick dielectric. So from a practical standpoint,
it would be tough to interface a high frequency package to a
60mil wide microstrip. What I read into this is that one may be able to
utilize a 10mil wide microstrip and run a narrow 2" long buss (4 to 8 bits
wide) at 2-5 Gb/s with a good package and good dielectric material
such as cyanate ester.

Are there any high speed folks such as the 10Gb/s SONET folks out
there that care to contribute?

Mike

On Jul 19, 5:05pm, WAUGH,RAY (HP-SanJose,ex1) wrote:
> 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.
>
> Ray
>
> _/ Raymond W. Waugh - WSD Diode Applications
> _/ E-mail: ray_waugh@hp.com
> _/_/_/ _/_/_/
> _/ _/ _/ _/ USPS : Wireless Semiconductor Division
> _/ _/ _/_/_/ 39201 Cherry Street, MS NK20
> _/ Newark, California 94560
> _/
>
> -----Original Message-----
> From: Stephen Zinck [mailto:zinck@cabletron.com]
> Sent: Monday, July 19, 1999 9:39 AM
> To: si-list@silab.eng.sun.com
> Subject: Re: [SI-LIST] : even-odd mode influence
>
>
> Ray,
>
> How long was the transmission line on this board? Have you had any success
> with transmission lines on the order of 18" long (@ 10 GHz) using FR-4?
> Just curious.
>
> Thanks,
>
> Steve
>
>
>
> [ Attachment (application/octet-stream): "pcb_matl.pdf" 46123 bytes
> Encoded with "base64" ]
>-- End of excerpt from WAUGH,RAY (HP-SanJose,ex1)

-- 
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Mike Degerstrom         Email:    degerstrom.michael@mayo.edu	
Mayo Clinic 
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