Gregg-
I concur with your understanding 100%.
Reflection phase with an open is zero degrees and is 180 degrees with a short. Reactive loads (inductive or capacitive) will have phase angles somewhere between 0 and 180 dependent on the reactance at a particular frequency which depends on reactance (Zl +jX or - jX).
See the last 2 sentences in the book section on Purely reactive loads that was cited.
Ray WB6TPU
Senior Signal Integrity Staff Engineer
(Retired)
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On Feb 19, 2021, at 7:52 PM, Gregg Messenger <techgreg@...> wrote:
?Where Roger and I have differed in the past is with regards to the concept of the S11 phase as measured by the nanoVNA.
While Roger has firmly stated in previous conversations that there is no relationship between the S11 phase and the phase change between voltage and current observed in reactive circuits, I still hold to my original thought that the voltage vs current phase of a reactive device is in fact related to S11 phase. It simply must be!
As the reactive component causes a change in phase of the voltage and current, so to does it cause a change in the S11 phase as measured by the nanoVNA.
Please see “Purely Reactive Load” in this reference:
(Ellingson)/03%3A_Transmission_Lines/3.12%3A_Voltage_Reflection_Coefficient
(Sorry, the link is not fully recognized, so one will need to cut and paste the link manually into a browser. I have included a screen shot with this post.)
The formula under the “Purely Reactive Load” heading for the voltage reflection coefficient clearly includes reactance. Where a reactive component is present, there will also be a change in phase between voltage and current at any given frequency.
Thus, I maintain that S11 phase is in fact related to voltage vs current phase.
Please feel free to prove me wrong.
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VE6WGM
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