# Setting up Reference planes with TRL Calibration using 8510.

Question asked by jkichline on Jun 10, 2008
Latest reply on Jun 12, 2008 by dgun
Sorry for triple posting. When I clicked "submit" it gave me an error so I tried two more times. I didn't realize it actuall posted... Can the moderators consolidate this into one post? Thanks!

Hi,

I am trying to understand exactly how to set up my reference planes in a custom TRL calibration. The goal is to measure capacitors from 1-5 GHz with the reference planes at the beginning of the mounting pads

I have designed my own CPWG TRL cal structures on Rogers 6010 (Er=10.2, Thickness=10mils, 1/2oz copper, TanD=0.0023).
W=9 mils, G=20mils.

I have a Thru (337 mils in length), a reflect (337mils in length), and a line (717 mils). I chose my line length to be 90Â° @ 3GHz (380 mils) plus my Thru Length. I also have a test structure with capacitor mounting pads. I'll try to sketch it here as best as I can...

Thru:
********
******          ******  GND
------------------------   SIG
------------------------
******          ******  GND
********

Reflect:
********
******          ******  GND
--------&#9488;      &#9484;---------  SIG
--------&#9496;      &#9492;---------
******          ******  GND
********

Line:
**********
**************             *************  GND
-------------------------------------------------   SIG
-------------------------------------------------
**************              *************  GND
**********

Test Structure
*******
***** &#9484;&#9488; &#9484;&#9488;******  GND
--------- |  |  -------  SIG
--------- |  |  -------
***** &#9492;&#9496;  &#9492;&#9496; *****  GND
*********

LineCalc tells me that my effective dielectric constant is 6.70 @ 3GHz. I used that to calculate my phase velocity (Vp=c/(Ee)^1/2)=1.158e8 m/s

If I want my reference planes to be 45 mils from the center of my thru (90 mil spacing), I calculate the time to be 19.74pS.

So I simply enter in 19.74pS as a delay for my thru for my calibration kit?
Is there a really good tutorial somewhere on how to set this TRL calibration up? Thanks!
-Jason