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Measurements >> RF Measurements >> Balun De-embedding
https://designers-guide.org/forum/YaBB.pl?num=1245915183

Message started by aaron_do on Jun 25^th, 2009, 12:33am

Title: Balun De-embedding
Post by aaron_do on Jun 25^th, 2009, 12:33am

Hi all,

I have a differential design which I want to partially characterize using a two-port network analyzer. The setup will include an off-chip balun at the input and output. I am able to calibrate the system up to the input of the baluns, but my calibration does not include the baluns or the wafer probes.

Does anybody know how I can de-embed the baluns+probes from the measurement? I can do a "through" measurement to get the combined S-parameters of both baluns and probes, but I need to know how to de-embed this from my DUT data.

My thinking is that I need to convert the convert the S-parameters into ABCD parameters, and then find the square root of the ABCD matrix in order to get the input and output ABCD parameters. Then I need to assume [ABCD,measured] = [ABCD,fixin][ABCD,DUT][ABCD,fixout] to find [ABCD,DUT] and convert this back to s-parameters. Does this sound correct? What is the easiest software to do this in?

thanks,
Aaron

Title: Re: Balun De-embedding
Post by aaron_do on Jun 25^th, 2009, 12:50am

It seems that the software used to measure the S-parameters and noise figure is able to de-embed the test fixture if I input a test fixture file. I'm told that I need to do an "open" measurement of the test fixtures fom input to output and then input this fixture file so that the software can automatically de-embed the entire test fixture (input and output).

Can the software really de-embed the entire test fixture with just a single "open" measurement? Note that S21 and S12 are zero, so the only info available is S11 and S22.

The name of software is NP_5 from Agilent but apparently its no longer in use ; except by me :D

thanks,
Aaron

Title: Re: Balun De-embedding
Post by pancho_hideboo on Jun 25^th, 2009, 3:46am

aaron_do wrote on Jun 25^th, 2009, 12:33am:

My thinking is that I need to convert the convert the S-parameters into ABCD parameters,
and then find the square root of the ABCD matrix in order to get the input and output ABCD parameters.
Then I need to assume [ABCD,measured] = [ABCD,fixin][ABCD,DUT][ABCD,fixout] to find [ABCD,DUT]
and convert this back to s-parameters.
Does this sound correct? What is the easiest software to do this in?

Use formulation based on Scattering Transfer Parameters(T-Parameters).
http://en.wikipedia.org/wiki/Scattering_parameters

If you have Agilent ADS, you can use the following.
http://edocs.soco.agilent.com/display/ads2009/De_Embed+and+De_EmbedSnP+%282-Port+to+12-Port+De-Embed+Data+File%29

aaron_do wrote on Jun 25^th, 2009, 12:50am:

The name of software is NP_5 from Agilent but apparently its no longer in use ; except by me :D

"NP_5" was shipped from ATN Inc not Agilent.
But currently it is shipped from the following.
http://www.maurymw.com/products/rfdcs/noisepar/solidstate/npseries.htm
http://auriga-measurement-systems.com/

Title: Re: Balun De-embedding
Post by aaron_do on Jun 25^th, 2009, 7:35am

Hi pancho_hideboo,

thanks for the help. Much easier to calculate directly from S-parameters. I have access to ADS but have never used it. I'll give it a go,

thanks,
Aaron