[SI-LIST] Re: Inserion loss of fr4 , 50 ohm trace .

  • From: bala <balaseven@xxxxxxxxx>
  • To: scott@xxxxxxxxxxxxx
  • Date: Sat, 23 Nov 2013 21:05:31 +0530

So stripline structure is strongly recommended for RF at 2.4Ghz?
Regards
bala
On 23 Nov 2013 20:44, "Scott McMorrow" <scott@xxxxxxxxxxxxx> wrote:

> The problem is most likely ENIG gold plating.  2.4 GHz is near the sweet
> spot for nickel resonance.  Nickel (a component of ENIG plating) has a
> resonance at approximately 2.7 GHz.
> Here are slides that Yuriy Shlepnev of Simberian and I created for the EMC
> conference paper that was presented several years ago  We show a detailed
> analysis of interconnect losses with Nickel and present a model for it's
> loss behavior.
>
>
> http://www.simberian.com/Presentations/NickelCharacterizationPresentation_emc2011.pdf
>
> Here is the reference for our IEEE paper.
>
> Y. Shlepnev, S. McMorrow, “Nickel characterization for interconnect
> analysis”, Proc. of
> the 2011 IEEE International Symposium on Electromagnetic Compatibility,
> Long Beach,
> CA, USA, August, 2011, p. 524-529.
>
>
>
> On Sat, Nov 23, 2013 at 9:51 AM, steve weir <weirsi@xxxxxxxxxx> wrote:
>
> > Demon nickel barrier could be the culprit.  In that case the simulation
> > model did not include the surface finish which is an easy way to get
> > surprised in the lab.
> >
> > Best Regards,
> >
> >
> > Steve.
> > On 11/23/2013 6:32 AM, Scott McMorrow wrote:
> > > Did you use gold plating on the CPW?  That is one source of potential
> > > additional loss.  Another is that your are not exciting the CPW mode
> > > correctly with your measurements and are measuring a different mode.
> > >
> > > On Sat, Nov 23, 2013 at 8:44 AM, bala <balaseven@xxxxxxxxx> wrote:
> > >
> > >> Sunil,
> > >> I would recommend to consider copper roughness and double check your
> via
> > >> and coplanar modeling in your simulation.I believe you considered the
> > loss
> > >> of your measurement cable.or simply generate s-parameter model from
> VNA,
> > >> check symmetric and passivity ,put that model in your sim setup and
> see
> > >> whats the loss.You shall definitely  get an idea.
> > >> Regards
> > >> bala
> > >> On 23 Nov 2013 18:33, "sunil bharadwaz" <sunil_bharadwaz@xxxxxxxxx>
> > wrote:
> > >>
> > >>> Hi friends ,
> > >>> We are designing a dual band receiver ( 2.4 Ghz & 5.5 Ghz ) on a Fr4
> > >>> substrate .
> > >>>
> > >>> The length of the 50 ohm RF trace ( CPW - 15 mil trace width & 18 mil
> > >>> spacing to ground ) ,
> > >>> is approximately 5 cms .We have simulated this 5 cms long CPW trace
> on
> > >>> HFSS using DK of
> > >>>
> > >>> 4.4 & DF  of 0.018 . The loss reported was about 1.6 dB .
> > >>>
> > >>> We have received the actual board , which shows about 6 dB loss for
> the
> > >>> same trace (actual measurement on VNA)
> > >>>
> > >>> Measured the 50 ohm trace with TDR . It shows about 53 to 54 ohms .
> The
> > >>> fab report is also
> > >>> in sync with the measurement on the impedance front .The test coupon
> (
> > >>> from fab  )also shows
> > >>> the right impedance .
> > >>>
> > >>> Why are we seeing such a huge insertion loss ? The DF of 0.018 seems
> to
> > >> be
> > >>> correct .
> > >>> I have double checked this number , with the fab .
> > >>>
> > >>> Can some one ( pls ) explain the inconsistency between the simulated
> &
> > >>> actual results  ?
> > >>>
> > >>> Best Regards
> > >>> Sunil.Bh
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> >
> > --
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