[SI-LIST] Re: Question on Rogers4350 loss
- From: steve weir <weirsi@xxxxxxxxxx>
- To: jose_moreira@xxxxxxxxxxx, <si-list@xxxxxxxxxxxxx>
- Date: Fri, 08 Apr 2005 10:16:20 -0700
Jose, Scott answered a similar question not long ago to a gentleman from
Xilinx. In his case the apparent loss / unit distance was about twice what
was expected, about 0.5dB / inch instead of 0.25 dB/ inch as I
recall. Scott pointed out that a major problem tends to be that because
the material has such a low loss, it is easy to get resonances that
through-off measurements, particularly of relatively short, ie low-loss
structures. You might try just extending your structure so that there is
enough loss to quiet down any resonances coming from your launches.
Steve.
At 06:00 PM 4/8/2005 +0200, jose_moreira@xxxxxxxxxxx wrote:
>Hi
>
>I would like to raise a question regarding to the dissipation factor =
>(tan d) of Rogers4350.
>
>My question is related to the problem posted by Ming Tsai some time ago =
>on the difference between measured and simulated loss of a microstrip in =
>Rogers.
>
>In my case I have microstrip with 21mil width and 10.2 inch length. When =
>I simulate the trace with the Rogers4350 specd value (~0.0037 at 10Ghz) =
>I get a insertion loss that is much higher that the measured values. On =
>my simulation I include a surface roughness factor of 1 micro-meter =
>which I would say is Ok. I also add the maximum guaranteed insertion =
>loss of the connectors. The connectors on my board are 2.4mm and I use =
>and optimized footprint obtained thorough 3D simulation by the connector =
>manufacturer.=20
>
>When looking for an answer to this problem I came across a presentation =
>from Chad Morgan from AMP where there is a slide with the measured =
>dissipation factor for several dielectrics and I see that for Rogers =
>they were measuring around 0.008!!.
>
>When I use this new value on my simulations I start to get some =
>reasonable correlation between simulation and reality.
>
>Has anyone looked into the real dissipation values for Rogers4350 and =
>other dielectrics (e.g. Rogers4003C) that you get on real boards??
>
>Best Regards
>Jose Moreira
>
>_____________________________________________________
>
>Jose Moreira
>Application Consultant
>STS Center of Expertise
>
>Agilent Technologies R&D and Marketing GmbH & Co.KG
>Herrenberger Strasse 130
>CCST-BUS
>D-71034 Boeblingen
>Germany
>
>Email: jose_moreira@xxxxxxxxxxx
>______________________________________________________
>=20
>=20
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