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Very basic questions on waveguide calibration

Question asked by drkirkby on Mar 19, 2013
Latest reply on Oct 22, 2013 by drkirkby
I downloaded the definitions of the Agilent X11644A X-band WR90 Calibration Kit

http://na.tm.agilent.com/pna/caldefs/87xx/WR90A1.htm

into my VNA (8720D) and tried to do a 2-port calibration, but I'm confused about a few things. 

1) Why is the system Zo on the VNA shown as 1 Ohm? Actually the waveguide definition file shows "System Z0 = 0.99999988079071 Ohm" which is even more confusing than 1 Ohm.  I was rather expecting it to be 377 Ohms (impedance of free space).

2) When I do 2-port calibration, the menus ask for the normal reflection, isolation and transmission standards. When choosing "reflection standards",  the reverse ones show: 

* Short 
* Lambda/4 short
* Fixed load

I expected this, as these correspond to short, open & load respectively in coax. But on the forward reflection standards, the VNA menus asks for 

* Short
* Lambda/4 short
* Line

I'm confused by this. What is one supposed to connect for the "Line?" I was expecting the last item to be "Fixed load", rather than "Line"

I know there is a section of waveguide call the "standard section", (Agilent part 00896-60008), but the X11644A's manual states "A standard section is used to check system operation *after* you complete a calibration." So I assume one does not use that in any way for calibration. The standard section was the item which is nearest to "Line" I could have thought of, but I'm puzzled why no load is requested on port 1. 

3) Is there anything +magical+ about the length of the standard section which is only used after calibration to check the calibration? 

4) Is there any application note which is an "Idiiot's Guide" to waveguide calibration?  

Dave

Edited by: drkirkby on Mar 19, 2013 9:29 AM

Edited by: drkirkby on Mar 19, 2013 9:36 AM  

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