[SI-LIST] Re: Via insertion loss

Hey, we need the stackup, connector style, launch geometry, destination layer. 
Are you blowing away the unused pads in the via?

A picture is worth a thousand words, show me the board.

Randy

> Date: Sat, 4 Aug 2012 12:08:14 -0700
> From: jory_mckinley@xxxxxxxxx
> Subject: [SI-LIST] Re: Via insertion loss
> To: praveenkumardr@xxxxxxxxx; si-list@xxxxxxxxxxxxx
> 
> Hello Paveen,
> You are hitting quarter-wavelength in the setup you describe below @ 
> approximately 5.9Ghz.  Can you get your second port to where you made your 
> cut(s)?  You can measure IL directly and will be able to see the resonances 
> if your LNA has enough bandwidth. 
> -Jory
> 
> 
> 
> 
> 
> From: Praveen Kumar <praveenkumardr@xxxxxxxxx>
> To: si-list@xxxxxxxxxxxxx 
> Sent: Friday, August 3, 2012 3:17 PM
> Subject: [SI-LIST] Via insertion loss
>  
> Hi all,
> I'm trying to find via insertion loss in a RF path that has a antenna
> connector on one end, followed by a trace (300 mils long) and then a via
> and again trace that connects to LNA.
> Now to find Via loss, all i'm doing is
> 
> first case : I measure S11 (path from Antenna-trace- via , cut the via
> trace on the bottom) from Antenna to "after-via" (open end).
> second case: I measure S11 (path from Antenna-trace on top just before it
> connects via,) from Antenna to "before-via" (open end).
> 
> thus i get return loss in both scenarios, with via and without via. The
> difference is return loss of via. half of this value is via insertion loss.
> 
> At 5 GHz I'm getting a value of 0.1 dB (actually little less than this)
> loss and increases to 0.6 dB at 5.9 GHz.
> 
> I repeated this for all the Cores (All three available RF Paths (from
> Antenna to Via) and got similar values.
> 
> The details are as follows here..
> RF path length : approximately 350 mils
> Number of layers : 8
> thickness: 1.6mm (with tolerance)
> via size: 20 mil pad - 10 mil drill (32 mil antipad).
> dielectric :PER IPC-4101/94, /95, /125, /128, /130 OR /131  (HALOGEN-FREE
> EPOXY-GLASS).
> 
> At the lower end of the frequency these values seem to be ok, but for
> higher frequencies via loss seem to be way more than expected.
> Do you feel the values are ok since it is at the extreme 5.9 GHz range only
> that the via loss value is at its worst ?
> 
> please let me know if there is anything wrong with the method followed ?
> 
> Thank you,
> Praveen
> 
> 
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