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E5071C Phase Difference Has Stair-Steps!

Question asked by kemeron on Jan 27, 2020
Latest reply on Mar 26, 2020 by mirek

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Hello,

I have E5071C configured to measure the phase difference between two oscillators on channels A and B. The sources of the VNA channels are, of course, disabled, and the reference input is the same reference for the two oscillators.

The phase measurements for the two oscillators exhibit discontinuous phase jumps, but always in tandem, so that the difference measurement shows no discontinuities. Several measurements and configurations have confirmed that it is the behavior of the VNA, and not present in the source.

What is the explanation for this? The phenomenon is causing heartburn for the project manager.

Many thanks in advance,

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mirek Mar 20, 2020 3:04 PM

Hello Kameleon

You measure that directly on sources with out any normalization? I will fist use single source, split the signal with power splitter that have minimum phase offset (restive splinter for example) and connect to both ports, and normalized. The receivers have some natural offset.

Regards,

mirek

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kemeron @ mirek on Mar 23, 2020 6:22 AM

Mirek,

Thanks for thinking about this issue, and your suggestions.

I had done precisely as you suggest, using a splitter on a single stable source to stimulate the VNA, and the phase discontinuities are still exhibited. This is how I determined that the discontinuities are in the VNA and not due to the sources.

The natural offset between receivers is not an issue, as I calibrate that out by exchanging the channels/leads to measure the true difference.

Still, the question persists of why are there phase discontinuities in the VNA?

Cameron

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mirek @ kemeron on Mar 26, 2020 4:09 PM

Hello Kameron

I wonder if the issue is the frequency. You are at 10 MHz. I might be that the internal clock (10 MHz) leak thru and interred with the signal.

regard.

mirek

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mirek Mar 20, 2020 3:04 PM
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Hello Kameleon
You measure that directly on sources with out any normalization? I will fist use single source, split the signal with power splitter that have minimum phase offset (restive splinter for example) and connect to both ports, and normalized. The receivers have some natural offset.

Regards,

mirek
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- kemeron @ mirek on Mar 23, 2020 6:22 AM
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  Mirek,
  
  Thanks for thinking about this issue, and your suggestions.
  
  I had done precisely as you suggest, using a splitter on a single stable source to stimulate the VNA, and the phase discontinuities are still exhibited. This is how I determined that the discontinuities are in the VNA and not due to the sources.
  
  The natural offset between receivers is not an issue, as I calibrate that out by exchanging the channels/leads to measure the true difference.
  
  Still, the question persists of why are there phase discontinuities in the VNA?
  
  Cameron
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  - mirek @ kemeron on Mar 26, 2020 4:09 PM
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    Hello Kameron
    
    I wonder if the issue is the frequency. You are at 10 MHz. I might be that the internal clock (10 MHz) leak thru and interred with the signal.
    
    regard.
    
    mirek
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E5071C Phase Difference Has Stair-Steps!

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