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

  • From: sunil bharadwaz <sunil_bharadwaz@xxxxxxxxx>
  • To: bala <balaseven@xxxxxxxxx>
  • Date: Sat, 23 Nov 2013 08:00:41 -0800 (PST)

Thanks Bala !! I will try that . Yes , the cable losses were already factored 
in & there are no Via's
on the RF line .
Regards
Sunil





On Saturday, November 23, 2013 7:15 PM, 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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