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4 port N-type/WR-284 calibration

Question asked by tj on Oct 12, 2015
Latest reply on Oct 31, 2015 by Dr_joel

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I've searched through previous posts about similar issues but still didn't find anything that helped...

I have a N5221A PNA, E-cal N4432A (for N-type), and a WR-284 Cal Kit from Maury (S7007S), and I'm attempting to make measurements on several 4-port directional couplers with the input/output ports being WR-284 and the coupling ports being N-type.

I originally thought I could use the couplers as unknown thrus, but the coupling factor spec for these couplers is 60dB and I believe the threshold for an unknown thru is 40dB...

Via Smart-Cal, I attempted to do a 4 port cal using my two kits, as well as the "Modify Cal" option. In the modify option, I selected
1) the two N-types to use the Ecal as their unknown thru
2) the two WG types to flush thru
3) one WG and one N-type port to unknown thru (where the other WG adapter would be used as the unknown thru)

I have several issues with the procedure. Firstly, the only WG standard asked for is the short, no loads whatsoever. Also, at the very end, the prompt asks for delay and phase offset, neither given values make a lick of sense.
The PNA provided:
Time delay= -1.#IND
Phase offset= -2147483648

Can someone advise the ideal way to calibrate the coax/WG combination? Either tweaking my above attempt or using a whole different approach (I could not figure out adapter removal method...)

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tj Oct 15, 2015 10:52 AM

Apparently my predicament isn't as trivial as I thought, as no one seems to have and suggestions on solving my issue.

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Dr_joel

@ tj on Oct 15, 2015 3:35 PM

Since you mention both type N and WG cal, I guess you coupler has two WG ports and two Type N ports?

In this case it might be best to do a 4 port type N cal. Then attached the WG to the two ports and do a second, 2 port TRL cal. Then use the cal-plane-manager to compute the de-embed network for the N to wave-guide adapter from the first 4 port cal and the second 2 port cal. Then, use the same calplane manager to de-embed the WG adapters from the two ports of the 4-port cal.

At least that's how I would do it.

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helenpt @ Dr_joel on Oct 16, 2015 3:16 PM

If the waveguide cal kit definitions include standards that allow for SOLT, and you define two ports as N and 2 as WG, can you just follow the wizard and do unknown through using coax-to-WG adapters?

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Dr_joel

@ helenpt on Oct 18, 2015 8:34 PM

Indeed, you can do exactly that, and that is what is normally done. But if you are going to mix TRL WG (easiest) with type N, I think it might be easier to do just the 4 port cal in type N, and then the TRL cal in 2 port and use cal-plane-manager.

If you have the 1 port standards (for waveguide it is usually short, offset short, load, offset load) then you have a lot more connections than TRL. but if you have one port standard, you can do QSOLT between the WG ports, and UT between WG and type N.

If you set it up right, you can have ports 1 and 2 WG, 3 and 4 type N, Set port 1 and 2 to WG and thru type defined and method QSOLT, then set a thru for ports 3 and 4, and type Ecal UT, and then a pair of thrus from 3-2 and 4-1 (need a WG to coax adapter) and then use UT (since the 1 port cals will have been already determined.

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tj @ Dr_joel on Oct 22, 2015 4:48 PM

Thank for the advice.

I'm attempting the de-embed/embed method, because attempting the QSOLT method causes the entire PNA application to shut down.

However, because I don't have the latest firmware (I'm running on A.09.50.13), I don't actually have the Cal Plane Manager. Can I still accomplish the de-embed/embed calibration method?
I do have the options "2 Port De-embedding" and "4 Port Embed/De-embed". Although I'm a bit confused, as the online instructions mention selecting the already done calibration as a S2P file, but the calibrations saved in my CalSet are not that format...

Not sure where to go from here.

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Dr_joel

@ tj on Oct 31, 2015 12:05 AM

In older code there was a macro function available called "characterize adapter" that did a quite similar thing. You will want to use the 2 port depembedding for this case.

But, if there is any way to swing it, I recommend you upgrade to newer firmware; in the last 2 years there has been giant strides in improving calibration using much better methods.

If QSOLT is causing a PNA crash, please contact me directly at joel_dunsmore@keysight.com. If we can reproduce it we can fix it.

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6 Replies

tj Oct 15, 2015 10:52 AM
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Apparently my predicament isn't as trivial as I thought, as no one seems to have and suggestions on solving my issue.
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- Dr_joel @ tj on Oct 15, 2015 3:35 PM
  Mark Correct
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  Since you mention both type N and WG cal, I guess you coupler has two WG ports and two Type N ports?
  
  In this case it might be best to do a 4 port type N cal. Then attached the WG to the two ports and do a second, 2 port TRL cal. Then use the cal-plane-manager to compute the de-embed network for the N to wave-guide adapter from the first 4 port cal and the second 2 port cal. Then, use the same calplane manager to de-embed the WG adapters from the two ports of the 4-port cal.
  
  At least that's how I would do it.
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  - helenpt @ Dr_joel on Oct 16, 2015 3:16 PM
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    If the waveguide cal kit definitions include standards that allow for SOLT, and you define two ports as N and 2 as WG, can you just follow the wizard and do unknown through using coax-to-WG adapters?
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    - Dr_joel @ helenpt on Oct 18, 2015 8:34 PM
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      Correct Answer
      Indeed, you can do exactly that, and that is what is normally done. But if you are going to mix TRL WG (easiest) with type N, I think it might be easier to do just the 4 port cal in type N, and then the TRL cal in 2 port and use cal-plane-manager.
      
      If you have the 1 port standards (for waveguide it is usually short, offset short, load, offset load) then you have a lot more connections than TRL. but if you have one port standard, you can do QSOLT between the WG ports, and UT between WG and type N.
      
      If you set it up right, you can have ports 1 and 2 WG, 3 and 4 type N, Set port 1 and 2 to WG and thru type defined and method QSOLT, then set a thru for ports 3 and 4, and type Ecal UT, and then a pair of thrus from 3-2 and 4-1 (need a WG to coax adapter) and then use UT (since the 1 port cals will have been already determined.
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  - tj @ Dr_joel on Oct 22, 2015 4:48 PM
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    Thank for the advice.
    
    I'm attempting the de-embed/embed method, because attempting the QSOLT method causes the entire PNA application to shut down.
    
    However, because I don't have the latest firmware (I'm running on A.09.50.13), I don't actually have the Cal Plane Manager. Can I still accomplish the de-embed/embed calibration method?
    I do have the options "2 Port De-embedding" and "4 Port Embed/De-embed". Although I'm a bit confused, as the online instructions mention selecting the already done calibration as a S2P file, but the calibrations saved in my CalSet are not that format...
    
    Not sure where to go from here.
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    - Dr_joel @ tj on Oct 31, 2015 12:05 AM
      Mark Correct
      Correct Answer
      In older code there was a macro function available called "characterize adapter" that did a quite similar thing. You will want to use the 2 port depembedding for this case.
      
      But, if there is any way to swing it, I recommend you upgrade to newer firmware; in the last 2 years there has been giant strides in improving calibration using much better methods.
      
      If QSOLT is causing a PNA crash, please contact me directly at joel_dunsmore@keysight.com. If we can reproduce it we can fix it.
      Like • Show 0 Likes0
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4 port N-type/WR-284 calibration

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