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What's the *best* way to determine if adapters are phase matched?

Question asked by drkirkby on Sep 19, 2012
Latest reply on Sep 20, 2012 by drkirkby
I have some 3.5 mm to N adapters

* 2 x Male N to female 3,5 mm
* 1 x Male N to male 3.5 mm
* 1 x Female N to male 3.5 mm
* 1 x Female N to female 3.5 mm

These adapters came with a 85033E 3.5 mm 9 GHz Calibration Kit I purchased used from eBay. These adapters were probably *not* supplied with the calibration kit when it was new, as the box the kit came in only has option 100 (female 3.5 mm to female 3.5 mm, P/N 85027-60005, which is unfortunately missing). 

As far as I can tell, from looking at the five N/3.5 mm adapters in the kits, and pictures on the Agilent web site, the adapters are *probably* Agilent ones, part numbers: 

Type-N -m- to 3.5 mm -m  1250-1743
Type-N -m- to 3.5 mm -f   1250-1744
Type-N -f- to 3.5 mm -f   1250-1745
Type-N -f- to 3.5 mm -m 1250-1750

which are supplied with option 400 for this kit, but as I said, the kit contents does not list these parts, or option 400.  

The 5 adapters I have do not have the Agilent name, and could be Chinese copies. I somewhat doubt this is so, as the quality is very high, but it is not impossible. 

I can think of a several ways I can probably check if these adapters are phase matched, but would like to know the *best* way.  

Is the electrical delay of the Agilent adapters published? (I note these adapters are all part of the "11878A 50 Ohm 3.5 mm Adapter Kit", but I don't see any mention of electrical delay in the manual for that kit.) 

I have access to an 85032B N calibration kit, which belongs to a friend, but I can borrow it if needed. (I also have one on order, but are begining to think it will never arrive). I have a 8720D VNA, which has option 010 (TDR) enabled. 

My inital thinking was:

* Calibrate the VNA with the 3.5 mm kit. 
* If I use the N cal kit, I know from http://na.tm.agilent.com/pna/caldefs/stddefs.html  the delay to the male short is 1.78E-11 s and to the female short is 9.30E-14 s 
* Put the unknown adapters on the 3,5 mm leads. 
* Terminate the adapters in N shorts. 
* Use the TDR mode (which I have never used), and find the time to the reflection. 
* If, after correcting for the different delays in the N shorts, the overall delay of shorts + adapters are always the same, then I can conclude the adapters are phase matched. 

I *think* this will work up to 6 GHz (the limit of the N cal kit), where the inductance of the shorts can be ignored. But what if I had a better cal kits, and wanted to check these adapters to a higher frequency, where the inductance of the shorts could not be ignored? If the adapters are what I think they are, then they are rated to 18 GHz, though none of the cal kits I have access to are. 

So what is the best way? 

Dave  

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