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VNA Reference Plane - RF Cafe Forums

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FL Techie
 Post subject: VNA Reference Plane
Posted: Tue Oct 04, 2005 9:17 am 
User avatar

Joined: Tue Jan 06, 2004 1:51 pm

Posts: 26

I need some clarification about the reference plane for on-wafer calibration & measurement using VNA and probe Station.

Can someone please tell me what determines the reference plane? How is it defined? Does it have to do with the dimensions of DUT and calibration artifacts?

Any info will be appreciated.

- Brad

 Post subject: vna reference plane
Posted: Sun Oct 09, 2005 6:57 pm 
User avatar

Joined: Wed Jul 06, 2005 5:54 pm

Posts: 28

Location: Germantown,MD


We choose the reference planes to calibrate out the additional structures like cables,pads,transmission lines etc., so that the data that we measure would be the data for the DUT being measured.

Once reference planes are fixed we can use appropriate math to calculate the S-parameters of the structure within the reference planes.

hope i answered your query in the right direction

 Post subject: 50 ohm reference question
Posted: Sat Oct 29, 2005 6:21 pm 

Joined: Sat Oct 29, 2005 6:08 pm

Posts: 1

Location: Portland, Maine

I need to calibrate a test fixture at a probe test point. I've built the fixture and the DUT looks about like an 0805 chip resistor (it isn't a resistor, but the physical size is representative). So, I need a similar chip which measures 50 ohms so I can calibrate the whole structure. I've read that 50 ohm chip resistors are not good things to use for this, and are only useful to about 500 MHz. I'm working around 1GHz. Anyone have ideas on how I can do this?



 Post subject: Re: 50 ohm reference question
Posted: Mon Apr 03, 2006 4:39 am 

Joined: Mon Apr 03, 2006 4:06 am

Posts: 8

Hi John,

Did you got a reply on your question? I might facing the same issue. We build our own calibration structure but know I want to evaluate them against commercial calibration structures. Did you consider to order calibration structures according to your footprint? Can you send me the article that suggests not to use in high frequency such a resistor?

Best Regards



R&S RF Application Engineer

 Post subject: Re: VNA Reference Plane
Posted: Mon Oct 11, 2010 11:14 am 

Joined: Mon Oct 11, 2010 9:52 am

Posts: 1

You might want to look at our product, Spectro VNA. Using Time Domain Substitution, you can move your reference plane to anywhere that you can temporarily create a short.

 Post subject: Re: VNA Reference Plane
Posted: Tue Oct 19, 2010 3:33 pm 

Joined: Sat Nov 08, 2008 11:35 pm

Posts: 30

Location: Ramona, CA

I recommend reading the Agilent app notes 8510-52 (PN5956-4352) and 8510-8A (PN5091-3645). The first is specifying calibration standards and the 2nd is using TRL standards for On-Wafer measurements. The calibration reference plane is defined by the physical structures and the definitions for the standards. It is typically set by the offset length of the thru, short and open. The TRL cal is better than SOLT (Short, Open, Load and Thru) for On-Wafer, but is suseptable to dispersion effects on GaAs below 1GHz and the lines become reactive. Agilent recommended LRM as the Load sets the reference impedance and On_wafer test results will be much better. Again the cal kit definition along with the physical structures will determine the reference plane. Also if using LRM be sure to measure the resistance of the loads and put into the cal kit so the measurment plane impedance is properly defined. The reference plane is usually either of two methods. In some cal kits they define the reference plane to be at the halfway point on the thru. The second and more typically used is to de-embed the reference plane back to some point (connection ground plane) or the probe tips or some other point on the launch structure or out on the line (mid point) for mechanical fixtures. I've used all the methods and it depends on what I am measuring which method I use.


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