multiline TRL calibration

[mfarhan1]

multiline trl calibration

Dear all

I am using a probing station for measurement of LTCC based circuit, The transition i am using is shown in figure,
I ll be using Multiline TRL calibration;

Now obviously transition impedence is not 50 Ohm it is 72 Ohms now as i am using THRU with zero length should the impedence of line be 50 Ohms or 72 Ohms according to Agilent application note (8510-8A calibration for non coxial measurements pp15 table 1) it is said that if you are using non zero length THRU then the impedence of THRU and LINE should be same, (mine is zero length THRU?)

2. It is also said that insertion phase of LINE should be 90 w.r.t insertion phase of THRU, at the same time it is said that the optimum length is 90 w.r.t center frequency, in my case both would be different so what should i do, frequency is 10-20GHz

3. In WinCalXE when you define probe type and pitch it ask for ISS to be specified and it will be used along with NIST TRL calibration, now in my case i am not using any predefine ISS but my own set of TRL kit on LTCC how do i change that option as it wont let me have custom ISS, if i click load button then it asks for *.wci file where would i get that?

Your help is really appreciated.

 

[burton]

nist multiline trl calibration

for TRL calibration:

(1) the systemic impedance is the impedance of line standard, the line and thru have the same impedance.

(2) the electrical length difference between line and thru standards is smaller than pi at the highest frequency, often (20-160) degree.

 

[mfarhan1]

@burton
Thanks, i know them from text books, but can you analyze my situation and tell me in accordance to that.
cheers

 

[nccu1990]

Normally the Network Analyzer impedance is 50 Ohm.

If you want to use 72 Ohm in the 50 Ohm VNA , I think that you should use the Matching pad (50 Ohm to 75 Ohm) and use the 75 Ohm cable.
75 Ohm more near the 72 Ohm impedance.

I don't see any 72 Ohm matching pad and cable can buy in the market.

Another solution is you can set abitrary reference impedance in VNA. This method used the math transform the impedance, it may be can work in multi TRL calibration.

 

[nccu1990]

I forward this problem to agilent forum.

Below is the link for their reply.
**broken link removed**

 

[kspalla]

How is my method is
1) select only 10%BW than 100%( 10 to 20GHz is huge)
2) Identify the nature like input or out put only i.e S11 and S22. or needs S21 also.
Alternatively
3) de-embedding the fixture section using software

 

[lil705]

Re: multiline trl calibration

Dear mfarhan1

The method of TRL calibration require the Line to match the terminal impedance (such as 50 ohm). Of course, you can change the terminal impedance

the same as the characteristic impedance of the "line" to let the line behave no reflection. You can use the standard TRL calibration as usual when you change

the terminal impedance properly.