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Agilent E8357A

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Miek:
I really think they're meant to be interpreted as two lists of complex numbers. If you do it that way you can see that the magnitude of the first list looks plausible - it's mostly continuous with a jump at 3 GHz where the source switches to using the 3rd harmonic of the synthesizer. In 2d, it's close to 1+0j at low frequencies then plots (roughly) a circle around the origin, which makes sense since there should be some cable delay in the test.

Given the text from the service manual:


--- Quote ---The receiver calibration is used to adjust the network analyzer receivers for a flat response
across its full frequency range. A power meter is connected to Port 1, as shown in
Figure 3-19, to establish a reference for flatness. A signal from Port 1, as shown in
Figure 3-20, is used to adjust the “B” receiver at Port 2. The adjustment is repeated using a
signal from Port 2 to adjust the “A” receiver at Port 1.
--- End quote ---

I expect that each file may only have the response from one receiver and the two files represent adjustment for each direction. Since the second list of complex numbers is purely real, this may be the power meter response and the first list is the A or B receiver response.

joeqsmith:
"interpreted as two lists of complex numbers."

"... each file may only have the response from one receiver and the two files represent adjustment for each direction. Since the second list of complex numbers is purely real, this may be the power meter response ... "

Thanks for the post.   This makes sense.    Any thoughts as why they do this at all?   Once they know the source is level, what do they gain?  The one thing I was thinking is I often don't calibrate the instrument and this would have the potential to tighten things up.   

Miek:
I think the goal is to meet the "Uncorrected system performance" spec. I would expect any of this error to be corrected by a full 2-port cal, so I don't think it's critical to do the adjustment.

I got quite in-depth looking into this on my E5062A. It came with only the transmission-reflection test set and I was able to enable the 2-port test set on it, and as part of that I had to generate the right calibration files to get good uncorrected performance. One was the "port characteristics" file, which turned out to be a standard 12 error-term calibration that gets loaded by default and overridden when doing your own cal.

I'd expect the PNA to have something similar somewhere and it should capture any error in receiver flatness, so it's odd to have a separate test & cal file, but the service manual has a clue - from the "Calibration Coefficient Test" it says:


--- Quote ---f the Analyzer Fails this Test:
• If the analyzer fails tracking error terms only, perform “Receiver Calibration
Adjustment” on page 3-44 and repeat this test.
• Failure of any other error terms indicate a hardware failure. Refer to the appropriate
error term discussion in Appendix A, “Error Terms,” for a typical cause of failure. Refer
to Chapter 7, “Repair and Replacement Procedures,” for instructions on replacing the
suspected faulty component or assembly.
--- End quote ---

Maybe they found that the other error terms are far more stable than the transmission tracking error and so they only adjust that. If they were to overwrite all of the error terms, it could hide damage to the calibration kit/ports/couplers.

joeqsmith:
I processed Forzaman's two files as complex and split out the two halves.  I think you are spot on.   


--- Quote ---I think the goal is to meet the "Uncorrected system performance" spec. I would expect any of this error to be corrected by a full 2-port cal, so I don't think it's critical to do the adjustment.
--- End quote ---

I am the worse when it comes to calibration and will typically only do it as a last step and if I am just looking for some rough idea and don't calibrate at all.   When I got the PNA, I noticed it's a bit more error than would have liked.  This alignment would certainly improve that.   

***
Correct freq index, aligned the two files vertical to easier see what is going on.

joeqsmith:
One odd thing I noticed, when I had the PNA create the two files if you look at the frequency table, both list 40MHz twice.  Any idea what is going on here?  Is this the point where they switch sensors? 

***
Replicates are also at 10M, 748M, 1.5G, 3G, 4.5G, 6G, 6.5G & 7.75G.   So something else is going on.   

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