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What does "Average Type" Refer To in Siglent SVA1032X "BW" Menu ???

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Someone:

--- Quote from: tautech on September 22, 2024, 02:38:23 am ---Thanks shabaz, that's my take on how things work too albeit with only limited SA experience over the last 10 yrs.
--- End quote ---
I think its on the other side, matching the diagram noisyee attached.

shabaz:
Interesting. I missed that diagram, I believe it must be correct, but I'm wondering if the result will be benign because after the averaging operation the value is converted back into the normal dBm power scale, so if averaging number is set to 1 (if possible) or disabled, then the result shouldn't change. But I'm really not sure. Maybe it does have an impact on other averaging that occurs in-between.
I looked at an R&S user manual and it positions those settings in the trace averaging menu, but that may just be a logical rather than physical placement.

Definitely worth a test. I just now quickly tried on a Keysight SA, I couldn't tell the difference when the trace average was off, but I only fed a sine-wave. I could try some more interesting signals tomorrow perhaps, and just eyeball if any difference is seen, admittedly it's not a very certain method.

starlite4321:
Hi shabaz, thanks for your thoughts.  Clearly something along those lines must be going on.  I was hoping someone who specifically knew what SIGLENT is actually doing in this particular case - specifically - might see the post.  I'll keep watching.

For others who don't understand the question, I'm going to stop repeating it now.  If interested, please carefully read any one of the many statements of it already in this thread.

Thanks

shabaz:
I tried it on a Keysight SA (which requires one of the three modes to be set in the BW config, i.e., it cannot be disabled, just like the Siglent).

The difference is easiest to see when the source is changing, i.e. using a noise signal as the input was effective.

As can be seen, when trace averaging is enabled, then the difference between the three modes is easy to observe.

However, without trace averaging, the traces for the three modes blend into each other, and they are indistinguishable.

Incidentally, I also tried an FM signal, but it takes a very fast sweep (e.g., by having a coarse RBW) so that there's a lot of change between sweeps for a difference to become visible. Then, the difference is extremely clear to see, but again, only with trace averaging. Without trace averaging, there's no difference that I could visually see between the three settings.

The above doesn't guarantee that there isn't any effect, since there could still be subtle differences, but it seems that practically speaking, the difference is not going to be observable, at least with typical settings, unless the trace averaging is enabled.

noisyee:

--- Quote from: starlite4321 on September 21, 2024, 05:34:16 pm ---Hi noisyee,  thanks for another reply.

Yeah, you're right, you can see the effects of "Average Type" in all the detect types all the time.  So it makes sense to put the control for it in a generic menu like BW from that point of view.

But it still doesn't explain what's actually happening.  What "averaging" is happening and where it is happening and for what reason ?  "Averaging" is not part of a basic (meaning averaging wasn't explicitly selected by the user) signal analyzer processing chain.  And again, even Siglent says the "Average Type" indicator will only show up when averaging is selected, which is not actually TRUE !  It always shows up as far as I can see.  So it's still not clear what's going on.  I can guess there's some averaging happening at the pre-detector stage or the post-detector stage or even as part of the detector function, but that's just guessing.  And I don't WANT it to always be averaging.  I want to be able to turn that off !

Anyway, thanks again for checking your Chinese manual noisyee.  At least it seems to provide a little more info than the US manual does.  If only I'd bought this from a competent, honest dealer with actual technical support.

--- End quote ---

Find a Keysight SA in lab, the Average Type is located in Meas Setting. The help doc doesn't help too, just as Siglent. :palm: Still have no idea how the SA behave when both Trace and Detect average are off. What's even more confusion is that Average Type in Keysight will affect sweep time even neither trace nor detect average is turned on. Maybe there are some other settings I don't find.
Only can assume the Average Type have little to no effect when there is no average and did some experiments by myself.
Trace Average Off, Detect Average Off, change Average Type: Almost no difference, but measured noise floor changes slightly
Trace Average On, Detect Average Off, change Average Type: Noticeable difference
Trace Average Off, Detect Average ON, change Average Type: More noticeable difference than Trace Average On

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