[SI-LIST] Re: symmetric coupled striplines...
- From: "Ishwar Hosagrahar" <ishwarh@xxxxxx>
- To: <bertsimonovich@xxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Tue, 1 Sep 2009 10:48:27 -0500
Hi Lambert,
Thanks for the crosscheck - I don't own E.Bogatin's book and your notes were
useful.
Does the book also provide any correlation of the equations to real-life
measurements? Or are the equations essentially model-fit to VNA-measured data?
I'd be interested in any correlation plots/measured S-data in the public domain
I could use for a simple trace experiment like this.
Regards,
Ishwar H
> -----Original Message-----
> From: Lambert Simonovich [mailto:bertsimonovich@xxxxxxxxxx]
> Sent: Monday, August 31, 2009 5:09 PM
> To: 'Ishwar Hosagrahar'; si-list@xxxxxxxxxxxxx
> Subject: RE: [SI-LIST] Re: symmetric coupled striplines...
>
> Ishwar,
>
> One way to sanitize your simulations is to estimate what your
> results should
> be using developed formulae if they exist. For example, in
> Eric Bogatin's
> book "Signal Integrity Simplified", there are formulae to
> approximate total
> attenuation of an interconnect due to the track and dielectric
> characteristics.
>
> A(cond)= -L*(36/(W*Zo))*sqrt(f)..........(eqn 9.65) pg 376.
> A(Diel)= -2.3*f*Df*sqrt(Dk)..............(eqn 9-69) pg 378.
>
> A(total) = A(cond)+A(Diel)
>
> Where;
>
> A(cond)= Attenuation of conductor
> A(Diel)= Attenuation due to dielectric
> A(total)= Total attenuation
> W = Trace width in mils
> f = freq in GHz
> Zo = Characteristic impedance of single trace in ohms
> Df = Dissipation factor
> Dk = effective Dielectic constant
> L = trace length in inches
>
>
> For the 6-9-6 Nelco-4000-13SI example, I ran the geometry in my field
> solver, and I assumed 1oz copper thickness. Using 53.4 ohms
> for Zo of a
> single trace, the estimated loss (Atotal) compared to your
> simulated results
> are as follows;
>
>
> Calculated Simulated N4000-13SI
> 1GHz -0.15dB -0.16dB
> 4GHz -0.39dB -0.38dB
> 5GHz -0.46dB -0.43dB
> 10GHz -0.78dB -0.81dB
> 20GHz -1.35dB -1.66dB
> 40GHz -2.41dB -3.55dB
> 50GHz -2.91dB -4.46dB
>
> As you can see, the calculation correlates fairly well (<5%)with your
> simulation up to 10GHz, so I would trust your simulated
> results for the
> Nelco-4000-13SI case. You can repeat for FR4 case.
>
> Hope this helps.
>
> Regards,
>
> Bert Simonovich
> Backplane Specialist and Founder,
> LAMSIM Enterprises Inc.
> http://lamsimenterprises.com/index.html
>
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx
> [mailto:si-list-bounce@xxxxxxxxxxxxx] On
> Behalf Of Ishwar Hosagrahar
> Sent: August-31-09 12:40 PM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: symmetric coupled striplines...
>
> Folks,
> I was pointed out that none of my attachments made it through
> the reflector
> - apologies. I am a newbie user to the list here.
>
> A sectional view of the HFSS model of the differential
> (uniform) symmetric
> stripline looks like the diagram below (but a lot prettier
> when viewed in
> the modeller view of HFSS) :-)
>
> ============================GND
> 8mil Dielectric Core
>
> ##SIG_P## ##SIG_N##
>
> 8mil Dielectric Core
> ============================GND
>
> The Sdd21/1inch values I got were (at a few interesting
> frequency points).
> As you can see, the loss curve is mostly linear across the
> frequency range
> when plotted on a Y-dB X-Hz plot for both dielectrics. The plot I sent
> didn't make it through either.
>
> FR4_epoxy Nelco4000-13SI
> 1GHz -0.28dB -0.16dB
> 4GHz -0.67dB -0.38dB
> 5GHz -0.77dB -0.43dB
> 10GHz -1.53dB -0.81dB
> 20GHz -2.99dB -1.66dB
> 40GHz -6.01dB -3.55dB
> 50GHz -7.43dB -4.46dB
>
> Comments appreciated.
>
> Regards
> Ishwar H
> ishwarh@xxxxxxxx
>
> > -----Original Message-----
> > From: Ishwar Hosagrahar [mailto:ishwarh@xxxxxx]
> > Sent: Friday, August 28, 2009 6:48 PM
> > To: 'si-list@xxxxxxxxxxxxx'
> > Subject: symmetric coupled striplines...
> >
> > Folks,
> > I was pondering about PCB trace losses in general to assess
> the impact
> > of migrating a couple of transmission lines to various dielectrics,
> > and hoping that some of the experts here can provide some inputs.
> >
> > As a part of the pondering process, I messed about with a
> HFSS model
> > of a symmetric differential stripline, and solved the differential
> > transmission loss/1inch of two different cases :
> >
> > case1 : FR4_epoxy, Dk = 4.4, Er = 0.02
> > case2 : Nelco-4000-13SI, Dk = 3.4, Er = 0.01
> >
> > (model had a 8mil thick dielectric for the symmetric
> stripline on the
> > top and bottom, and I adjusted the (default
> > copper) trace widths to get a 100ohm differential impedance
> for both
> > cases. With a trace gap of about 9mils, the traces were
> between 6mils
> > to 8mils wide depending on dielectric. The simplistic material
> > definitions were from the default Ansoft library, ie.nothing too
> > intelligent was attempted. A picture of the model is attached here)
> >
> > Without getting into the numerous technical details of the
> solver or
> > the setup (choice of solution and port types, excitations, boundary
> > conditions, complex dielectric definitions, surface roughness
> > factors/layered impedance etc.etc.), do the HFSS results look
> > believable to folks here with more experience on all this sort of
> > complicated thing?
> >
> > My questions are :
> > (a) does anyone have measured data (or an intuitive feel)
> to judge if
> > the FR4 and Nelco4000-SI results are realistic in terms of what I'd
> > get from a VNA measurement if I were able to ideally deembed any
> > connections and measure the uniform symmetric stripline
> > characteristics for this specific topology?
> >
> > (b) anyone on this list know of published data for loss/inch
> > characteristics of different trace topologies (uniform symmetric
> > stripline) for different dielectrics? I am looking for
> actual measured
> > or simulated data for different dielectrics on the lines of Joel
> > Goergen's qualitative comparison to the IEEE at :
> > http://grouper.ieee.org/groups/802/3/ap/public/may04/goergen_0
> 1_0504.pdf
> >
> > The Sdd21 plot of my analysis is attached. I'll be happy to
> > send anyone the actual Touchstone-formatted S-parameters
> > [S4P] if you want to take a deeper peek at the data. (I can't
> > figure out how to post the data zipfile to the si-list
> > reflector submissions area, so please email me directly at
> this time)
> >
> > Thanks for inputs.
> >
> > Cheers,
> > Ishwar Hosagrahar
> > ishwarh@xxxxxxxx
> >
>
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