Hello fellow technical experts,

I intend to measure a DUT's S parameters. my DUT is a very thin piece of material will be sandwich between a pair of waveguides.

since the transmission medium is a waveguide, i cant use the default calkit.

Hence i used the TRL calibration method.

I've read numerous technical paper and application notes regarding TRL calibration. but non of them describe in detail how to do the post calibration calculations. They only mention what are the standards required.

TRL=thru reflect line.

Thru: i have connected the waveguides without the DUT and measure the S parameters (S11, S12, S21, S22)

Reflect: connect a shorting plate to both waveguide opening and measure all S parameters.

line: insert a section of waveguide and measure its S parameters.

next i insert my DUT and measure its S parameters.

Now i have in my possession, the S parameters (of T,R,L, and DUT) magnitude and phase, from 6-12GHz

Now what should i do next? what kind of calculation should i do to get the calibrated S parameters of my DUT.

I've read the fundamental paper on TRL calibration from here.

http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=1129778

but it did not mention how to do the post calculations.

Please help me, i really need to know the way to get the calibrated S parameters.

Many thanks!

I intend to measure a DUT's S parameters. my DUT is a very thin piece of material will be sandwich between a pair of waveguides.

since the transmission medium is a waveguide, i cant use the default calkit.

Hence i used the TRL calibration method.

I've read numerous technical paper and application notes regarding TRL calibration. but non of them describe in detail how to do the post calibration calculations. They only mention what are the standards required.

TRL=thru reflect line.

Thru: i have connected the waveguides without the DUT and measure the S parameters (S11, S12, S21, S22)

Reflect: connect a shorting plate to both waveguide opening and measure all S parameters.

line: insert a section of waveguide and measure its S parameters.

next i insert my DUT and measure its S parameters.

Now i have in my possession, the S parameters (of T,R,L, and DUT) magnitude and phase, from 6-12GHz

Now what should i do next? what kind of calculation should i do to get the calibrated S parameters of my DUT.

I've read the fundamental paper on TRL calibration from here.

http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=1129778

but it did not mention how to do the post calculations.

Please help me, i really need to know the way to get the calibrated S parameters.

Many thanks!

in page 217, There is a section about TRL calibration.

This is exactly the information i am looking for. Which is how to do the calibration calculation.

But there is a new problem. The method mention in this book does not seem to work.

Lets me summarize how Mr Pozar steps.

The error can be represented by a pair of error box sandwiching the DUT.

First measure the S parameters for the T,R,and L standard.

From the S parameters of T,R,&L, a formula can be used to calculate the error box S parameters.

Then the error box S parameters is converted to ABCD parameters and multiply in matrix form to find the DUT ABCD parameters. finally convert back the ABCD parameters of the DUT back to S parameters.

The problem encountered is, at the first step, equation 4.78 at page 220.

There will be 2 answer for this equation, in order to find the correct answer, both the real and imaginary of gamma (propagation constant) must be positive. This is the problem, neither answer of equation 4.78 gives both real and imaginary positive. out of 201 data points that i have, 107 of them do not satisfy this condition.

Please have a look and see whats wrong with Pozar's equation.

Are there any other books or methods that shows how to perform calibration calculation using TRL measured S parameters?

if you guys know any, please recommend them to me. I will be deeply grateful.

Thank you

Edited by: odanzy on Apr 30, 2012 9:26 AM - Removed pictures of copyrighted material