Weird resolution filter shape of SSA3021X+ at specific frequency - Page 1
Forum section: electronics / testgear

author: erikka
author_rank: Regular Contributor
timestamp: December 04, 2021, 11:33:53 am
content: During some testing using an H-probe I observed a very weird shape of the resolution filter of the SSA3021X+ at a very specific frequency (12.08MHz)The weird shape is independent from the RBW down 30kHz, below 30kHz the SA switches to FFT mode and the shape becomes normal again.The weird shape could not be reproduced by using a signal generator as input.Anybody any clue of what is happening??

author: tautech
author_rank: Super Contributor
timestamp: December 04, 2021, 07:55:05 pm
content: Which FW version ?H field implies EMI measurements, you need engage the EMI filter or maybe use EMI mode.

author: eloso
author_rank: Regular Contributor
timestamp: December 04, 2021, 08:37:41 pm
content: I think more information may be useful. With a wide resolution bandwidth I would expect a signal picked up with the probe to have what may be termed "odd" shapes, or not to be visible at all. The signal you are looking at is no doubt wider than anything you are producing on the SigGen so it is not suprising that you cannot reproduce it with that either.Could you show this same slice of spectrum with some varying RBWs ?Eloso

author: erikka
author_rank: Regular Contributor
timestamp: December 05, 2021, 07:45:16 am
content: I'm not doing a real EMI measurement, just picking of some radiation.The span was set to 10MHz and the RBW to 1MHZ so one would expect the normal RBW response but enlarged due to the 10:1 span:RBW ratio but the sides of the resolution filter response where cut off.

author: Joel_Dunsmore
author_rank: Regular Contributor
timestamp: December 05, 2021, 10:45:58 pm
content: No idea for sure, but a guess. Looks like a band switch point and likely some freq is not set correctly so the left side is shifted up more than it should be. Might also be that the filter you request is not available in the lower frequencies and you are seeing a goofy result where the filter is computed from data acquired, but the acquisition is not good due to other hardware limitations in low band.

author: tautech
author_rank: Super Contributor
timestamp: December 05, 2021, 11:26:02 pm
content: Quote from: erikka on December 05, 2021, 07:45:16 amI ask again, which firmware version ?Try with the latest:https://int.siglent.com/upload_file/zip/firmware/Spectrum_analyzer/SSA3000X%20Plus_V3.2.2.5.0_EN.zip

author: jjoonathan
author_rank: Frequent Contributor
timestamp: December 05, 2021, 11:29:42 pm
content: Could it be a slow sweep turning variable amplitude as a function of time into variable amplitude as a function of frequency? The width of the chunky bump would take a few milliseconds to sweep and that sounds like a plausible packet time to me (and it would be multiplied by the RBW response anyhow).If it's the exact same shape on every sweep over multiple sweep times, that would be evidence against this theory. There would have to be a synchronization mechanism. Do you have any triggers active?

author: erikka
author_rank: Regular Contributor
timestamp: December 06, 2021, 06:57:17 am
content: The FW is 2.2.1.2.8.The amplitude of the signal was constant and no triggers where active.And its exactly the same over multiple sweeps

author: tautech
author_rank: Super Contributor
timestamp: December 06, 2021, 07:05:06 am
content: Quote from: erikka on December 06, 2021, 06:57:17 amThe latest, 3.2.2.5.0 is 4 versions later. Time you bit the bullet and upgraded !The link is just a few posts ago.

author: erikka
author_rank: Regular Contributor
timestamp: December 06, 2021, 02:43:37 pm
content: Upgrade doneHope this is solved.

author: tautech
author_rank: Super Contributor
timestamp: December 06, 2021, 08:22:57 pm
content: Quote from: erikka on December 06, 2021, 02:43:37 pmMe too, however do note it is fundamentally wrong to report what might be a bug without the latest firmware installed as you could be chasing shadows that are just not there in the latest firmware.What you have seen may be related to a recently reported spur but it might not be too.We look forward to your checks.