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

[starlite4321]

Totally confused !  I just bought an SVA1032X (word of advice, don't ever buy anything from Liberty Test Equipment - terrible !).  There is a setting in the "BW" menu called "Average Type" with no useable explanation of which "averaging" operation in the device it actually controls.  The manual says, "When Trace Average is on, the average type is shown on the left side of the display".  However the average type selected there is ALWAYS shown on the left side of the display no matter what is turned on and off - anywhere.  And there's no "Average" setting IN the BW menu, just this "Average Type" setting.  Does anyone know what this setting is actually DOING ?  Which average function does it pertain to ?  Why is it ALWAYS shown in the display ?  I've been trying to get the simplest answers from Siglent support here in the US but they are absolutely USELESS !!  There doesn't appear to be any competent source of support for Siglent questions and problems.  I'm almost beginning to wish I'd never heard of Siglent for confusion like this !

[newbrain]

The manual, in chapter 2.2.1.4, will tell you what the average types are and what kind of measuremente they are best suited for:

2.2.1.4 Average Type
Choose one of the following averaging types: log power (video), power (RMS), or voltage averaging.
When trace average is on, the average type is shown on the left side of the display.
1. Log Power
Select the logarithmic (decibel) scale for all filtering and averaging processes. This scale is "Video"
because it is the most common display and analysis scale for the video signal within analyzer. This
scale is excellent for finding Sine/CW signals near noise.
2. Power Average
In this average type, all filtering and averaging processes work on the power (the square of the
magnitude) of the signal, instead of its log or envelope voltage. This scale is best for real-time power
measurement of complex signals.
3. Voltage Average
In this Average type, all filtering and averaging processes work on the voltage of the envelope of the
signal. This scale is suitable for observing rise and fall behavior of AM or pulse-modulated signals such
as radar and TDMA transmitters.

Each trace can be set to different modes, according to chapter 2.2.2.2:

1. Clear Write [...]
2. Max Hold [...]
3. Min Hold [...]
4. View [...]
5. Blank [...]
6. Average
Set the averages times of the selected trace.
More averages can reduce the noise and the influence of other random signals; thus highlighting the
stable signal characteristics. The larger the averages times is, the smoother the trace will be. Enabling
averaging will take more time to collect the full spectral information because the analyzer needs to
sweep the set average count. The displayed data is averaged in a first-in-first-out fashion.

When a trace is set to Average mode, the calculation of the average is done according to the selected Average Type and number of sweeps (1..999).

Disclaimer: I do not own this instrument, I just read the manual...

[starlite4321]

Hello newbrain,

Thanks for the reply.  Of course, I read the manual too as you can clearly see from my post.  And it is absolutely NOT clear that the average "Types" in the "BW" menu refer to an averaging function you indicate provided over in the "Detect" menu anymore than the averaging parameters set over in the "Trace" menu or anywhere else.  It seems to be referring to some averaging bandwidth associated with the detection function that the menu the setting is actually IN - the BW menu - is related to though that's not explained.  And there's no explanation at all of the statement "When Trace Average is on, the average type is shown on the left side of the display" when the average type selected there is ALWAYS shown on the left side of the display no matter what is turned on and off - anywhere.  For example, when the item you list is NOT set to "Average Video" - say "Pos Peak" - the average "Type" is still shown on the left side of the display.  What is being averaged then ?  Sorry, I don't think your explanation actually explains this at all.

But thanks for trying anyway - much appreciated !

[tautech]

Which firmware version are you on starlite ?
Latest is 6.2R5

BW averaging AFAIK is to do with the acquisition method as we see some setting change with the type.

A few screenshots so we are all on the same page....

[starlite4321]

Hi Tautech, thanks for the reply.

I just got it a few days ago and immediately updated to the latest version, v3.2.2.6.2R5 as you say.  (by the way, take my advice and don't ever buy anything from "Liberty Test Equipment" - horrible retailer.  Run for your life !)

Yeah, you can definitely see differences among trace types with different "Average Type"s set, including those other than the average setting which is another reason I know the previous response is incorrect.  But this happens when the SVA is in heterodyne mode where there are filters both before and after the detector, but there isn't supposed to be any averaging.  The way this works sort of implies there IS some kind of averaging ALWAYS going on whether you like it or not.  If Siglent's support weren't so useless it might be possible to get an answer from them.  But unfortunately...

Again, thanks for the reply !

[Someone]

https://siglentna.com/application-note/spectrum-analyzer-basics-detectors/
Averaging at the sampling stage, not the trace stage.
https://www.keysight.com/blogs/en/tech/rfmw/2020/07/31/spectrum-analysis-basics-part-3-detector-types

[tautech]

Yeah, you can definitely see differences among trace types with different "Average Type"s set, including those other than the average setting which is another reason I know the previous response is incorrect.  But this happens when the SVA is in heterodyne mode where there are filters both before and after the detector, but there isn't supposed to be any averaging.  The way this works sort of implies there IS some kind of averaging ALWAYS going on whether you like it or not. 

Sure but you can step around BW averaging if you use a Max or Min Hold instead of CW.



Have a play with these ....

[noisyee]

Interestingly, there is a block diagram in Chinese version (UM0703 C02E) user manual. It seems Average Type in BW had caused many confusion.
Average Type selector fall between RBW and Detect. It's an additional IF signal process when Trace Average is ON.

[starlite4321]

Thanks for the response noisyee.

I'm not surprised it's caused a lot of confusion.  Wouldn't it be nice if Siglent made any effort at all to explain it ?

Regarding your comment, "It's an additional IF signal process when Trace Average is ON.", then why does "Average Type" effect traces even when Trace Average is off ?

[starlite4321]

Hi someone, thanks for the response !

The articles in those two links sort of explain the same thing the Siglent manual does about detector types.  That doesn't really help.  The question here is, what is this "Average Type" setting in the BW menu doing ?  That setting has an effect on ALL the detector types, including the ones that aren't "Average" that according to the Keysight article simply connect the dots of the detection points.  Thanks for the links though.

[noisyee]

Thanks for the response noisyee.
I'm not surprised it's caused a lot of confusion.  Wouldn't it be nice if Siglent made any effort at all to explain it ?
Regarding your comment, "It's an additional IF signal process when Trace Average is ON.", then why does "Average Type" effect traces even when Trace Average is off ?

Checked again, manual says it will affect not only trace average but also detect average. That make sense because the Average Type is processed before detect and trace display.
My assumption is there is no other proper menu to place the Average Type, cause it will affect every trace and both Trace Average and Detect Average. Placed in BW menu is confusion, but at least it's a global setting.

[starlite4321]

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.

[tautech]

The doc member Someone linked under Average Detection explains much......but why HPAK waffles on about buckets instead of Bins is a new one to me.
https://www.keysight.com/blogs/en/tech/rfmw/2020/07/31/spectrum-analysis-basics-part-3-detector-types

[Someone]

The doc member Someone linked under Average Detection explains much......but why HPAK waffles on about buckets instead of Bins is a new one to me.
https://www.keysight.com/blogs/en/tech/rfmw/2020/07/31/spectrum-analysis-basics-part-3-detector-types

The entire chain is a hold over from historical implementations, to maintain backwards compatibility with existing procedures/tests. It could be much simpler and more useful. Some users aren't particularly technical so I can see where a dumbed down bins/buckets explanation was needed.

[starlite4321]

Thanks for the comment tautach.

Yeah, I read through this when it was posted here.  It's just yet another simplified explanation of how SAs work.  The internet is full of them.  I'm not sure there's that much in it that isn't already in the not-too-great Siglent manual itself.  Unfortunately, it doesn't explain this question at all.  noisyee commented that he's seeing that this setting has caused a lot of confusion.  I wish Siglent would simply explain it somewhere.  The manual would be the obvious place.  And of course, if I'd bought it from any competent retailer instead of Liberty Test Equipment, they could use their influence to get the question past Siglent's useless customer support to someone at the factory who actually knows what they're doing.  Unfortunately ...  I'm sure feeling the case for paying the price to buy test equipment from name brand companies through major retailers, that's for sure.

[tautech]

The manual, in chapter 2.2.1.4, will tell you what the average types are and what kind of measurements they are best suited for:

Disclaimer: I do not own this instrument, I just read the manual...

Later version is here:
https://int.siglent.com/u_file/download/24_05_17/UserManual_UG0703P_E02E.pdf

[starlite4321]

Thanks for another response tautech,

Yup, that's the one I've got.  As I mentioned, I just bought it therefore I just downloaded the manual so it's the latest version.

Again, newbrain whose post you quoted here didn't understand the question.  Of course the manual describes what the averaging types are.  And the posts with external references like the one from Keysight just explain the same thing all over again and don't help at all. 

Once again, the question is, what averaging is the "Average Type" setting controlling ?  Where is it happening and how do you TURN IT OFF !!   NOT WHAT AVERAGE TYPES CAN BE SELECTED - which is clearly shown in the manual as keeps being pointed out over and over again.  Because as has been made clear here many times, it's not the "Trace Type" in the Trace menu, and it is not the "Average" settings in the Detect menu.  Because you can turn those off and the "Average Type" setting still affects the trace in the display.  And the type that has been selected is ALWAYS listed on the left side of the display. No setting that I can find turns it off despite what the manual says !

[Someone]

Because as has been made clear here many times, it's not the "Trace Type" in the Trace menu, and it is not the "Average" settings in the Detect menu.

Average detector can use several different "laws", which are selected in the BW menu on these instruments. Where is the confusion?

Do you have any evidence of the result being affected when you change the BW averaging type while the detector is set to the Pos Peak, Neg Peak, or Sample modes ?

[shabaz]

Hi,

Inside the spectrum analyzer, there are several locations where averaging "stuff" can occur.

There's one location, near the end of the processing path, called the trace average on most spectrum analyzers. At that location, the trace average can be either:
    * log-power, or
    * power, or
    * voltage mode averaging.

All three are indeed averaging methods. And they are likely to appear in the Bandwidth configuration menu. Consider them as children of the "trace average" function which is the parent.

Those children settings have zero effect on the trace when the parent (trace average) is off.

Keysight/Agilent/HP have a sort of unwritten convention, that many of their spectrum analyzers always display the child averaging type on the screen, regardless of whether the parent "trace averaging" is on or off. The child technically doesn't exist without the parent, but the child type is still displayed. This probably goes back decades, and people don't like changing conventions sometimes even if it doesn't make sense. Please note that I'm speculating, I wasn't around at the time, I've merely used a few SAs and have seen that child value displayed always, it's permanent.

On one of the screenshots in reply #3, the way you'd tell if that trace averaging was enabled, is to see if a number is present in that yellow text I believe (I don't have a Siglent SA). I've reproduced it in the attachment below. You can see the number 94 (yellow arrow in my attachment) and it has not quite reached 100 yet, which is the set value of the number of sweeps for averaging (red arrow). So, the averaging type (LogPwr) in the blue box on the left is valid.

If there was no number in yellow, then that means that the blue box item on the left has no effect. As mentioned, this is convention.

You can test on your spectrum analyzer that this is true, because if trace averaging is switched off, then regardless of that child setting, you'll see no difference on the trace (if you do, then that's a question for Siglent to justify! : ).

So, if you don't want averaging to apply at that location inside the spectrum analyzer, then you'd have to turn off trace averaging, and simply accept that the text is there unfortunately.

[tautech]

Thanks shabaz, that's my take on how things work too albeit with only limited SA experience over the last 10 yrs.

The 100 Average screenshot captured at 94 sweeps was entirely intended if nothing more than to show how it removes H&L peaks compared to the other screenshots in that group.

[Someone]

Thanks shabaz, that's my take on how things work too albeit with only limited SA experience over the last 10 yrs.

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]

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.

Find a Keysight SA in lab, the Average Type is located in Meas Setting. The help doc doesn't help too, just as Siglent. 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