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ENA5071C absolute measurments

Question asked by aleberto69@gmail.com on Mar 11, 2014
Latest reply on Mar 26, 2014 by aleberto69@gmail.com
I need help about Absolute Measurement with ENA 5071C.
I refer to the direct access to the absolute R1(n) R2(n) ... A(n), B(n) measurements ( n being the port where the stimulus is applied)  ( measurement menu).
I tried to perform some " special" calibrations using that parameters and together with the math capability of the instrument, instead of using normal S parameters.. Unfortunately my algorithms didn't work as I would have expected.
After investigations I found some inconsistency about what I suppose that  the absolute measurement  are.
Namely
1) I used just port 1 and port 2 ( so that R1,A,R2,B are the involved measurements)
2) Connect port 1 and 2 with a 50 ohm cable ( 1m) and perform measurement at about 100 MHz ( few points to easily verify the results)
3)I measured  R1(1), A(1),R2(1) and B(1) and  normalize the 4 measurement to the value of the first one ( R1(1)) 

so that...
-R1(1)/R1(1) is 1  (obvious)
- as expected B(1)/R1(1) is in modulus close to 1 ( signal propagating through the cable and entering in port 2)
- as expected A(1)/R1(1) is small ( representing the reflected wave coming back into port 1) supposing this means that port 2 is rather matched (load match)
- as I didn't expect R2(1)/R1(1) result in modulus about 0.4 instead to be rather small ( as A(1)/R1(1))..

If R2(1)/R1(1) is proportional to the wave outgoing from the port2 ... I could understand that this could at least be not small...( It means that the port is not well matched) but in this case I also expect A(1)/R1(1) to be similarly not small as well ..

Identical things happens using other ports and in all the possible Direction" ( stimulus position)

With this inconsistency is it now clear why my algorithm is not working properly.

Is there somebody that could explain the behavior of R2(1) or suggest documentation and more information about this absolute parameter?

In the ENA 5071C manual there is just a brief mention to those measurement with very few explanation..


There is also another mystery...

Why the above 4 parameters  are not constant in phase from sweep to sweep?
I could verify that the relative phase is stable ( after normalization the phase is stable from sweep to sweep), but is not clear why it isn't stable the absolute phase of each of them...
"May be an architectural question" I told myself .....

Thank you in advance to everybody...
Regards
Aleberto69  

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