Spectrum Analyzer noob question. How can I time correlate frequency domain..   - Page 1
Forum section: electronics / beginners

author: supperman
author_rank: Regular Contributor
timestamp: January 27, 2020, 09:01:57 pm
content: So I have been very interested in what the Tektronix MDO4000 can do with time correlating the spectrum analyzer with the signal system (time domain). Is this really the only way to do it or can any spectrum analyzer be setup with a separate scope to work in a similar way?Here is the use case I'm trying to address (without buying an MDO4k):I believe I have radiating issues in my design that are created by specific signals on the PCB. These signals occur only under specific conditions. My understanding of the MDO4k is that it can record time-slices of spectrum data and as you search through the time domain looking at signal transitions you can get a small "window" into the spectral emissions that correlate to the signal changes. Super cool.How do I do that with a stand-alone SA? Can I trigger it / segment it in similar ways and then correlate it back to a scope to the time domain? I have never worked with an SA. I'm guessing you can trigger on specific frequency spikes? But how can you go back and check what time-domain transitions happens at the time?And if this is possible.. can you do this with any SA or are these especial features of only a few.

author: eb4fbz
author_rank: Regular Contributor
timestamp: January 27, 2020, 09:24:43 pm
content: You can do that with a realtime spectrum analyzer triggered by the oscilloscope. I have done that with a RSA3408A.

author: supperman
author_rank: Regular Contributor
timestamp: January 27, 2020, 10:33:29 pm
content: Quote from: eb4fbz on January 27, 2020, 09:24:43 pmSo "real-time" is a key word. Not just a marketing term? So some Rigol Models work.. but Siglent does not?I do see trigger windows in the us mentioned on Rigol models.Of course if the SA costs as much as a used MDO4k.. I guess I would just buy the MDO4k and sell my current scope to help with the budget.

author: KE5FX
author_rank: Super Contributor
timestamp: January 27, 2020, 11:58:01 pm
content: The Agilent DSO/MSO6000 series of scopes (and presumably the 5000 and 7000 models) provides the same triggering for its FFT display as it does for the rest of the waveform acquisition process, so that might be one option.They can actually do a lot of things that the Tek MDO marketing literature might lead you to believe are brand-new features that have never been available in any form. That's probably true of many scope models, but I'm only familiar with triggered FFTs on mine.

author: supperman
author_rank: Regular Contributor
timestamp: January 28, 2020, 12:28:27 am
content: Quote from: KE5FX on January 27, 2020, 11:58:01 pmThanks. Yes, I think that is my understanding in general.. if you scope is fast enough (both into the 2-3Ghz range, and processing) then FFT can approximate the function of a realtime SA.I did a bit of a dive.. and Rigol RSA3k seems to be a great option.. especially with the EMI software and real time capability. $1,600 with Rigol level "security" as far as higher bandwidth and options unlocking..Does anyone disagree? Would this work for time domain triggered spectrum analysis?

author: David Hess
author_rank: Super Contributor
timestamp: January 28, 2020, 02:51:54 am
content: Quote from: supperman on January 27, 2020, 10:33:29 pmA spectrum analyzer which accepts a trigger input is the key phrase. This essentially comes for free if your oscilloscope is doing the spectrum analysis.