Products > Test Equipment
Why R&S name some models Signal and Spectrum Analyzer
<< < (2/2)
pdenisowski:

--- Quote from: G0HZU on June 04, 2024, 10:59:53 pm ---Obviously, the manufacturer will not be keen to draw attention to this SFDR limitation of a wideband signal analyser when it is compared to a spectrum analyser. So you are unlikely to find this stuff described in the marketing literature.

--- End quote ---

The SFDR within the analysis bandwidth is actually the third "key fact" in our FSW marketing brochure (see attached) :)

https://scdn.rohde-schwarz.com/ur/pws/dl_downloads/pdm/cl_brochures_and_datasheets/product_brochure/5215_6749_12/FSW_bro_en_5215-6749-12_v1600.pdf

I made an entire video explaining dynamic range (and SFDR) in spectrum analyzers because we absolutely want people to understand this specification :)

G0HZU:

--- Quote from: pdenisowski on June 05, 2024, 01:55:40 am ---
--- Quote from: G0HZU on June 04, 2024, 10:59:53 pm ---Obviously, the manufacturer will not be keen to draw attention to this SFDR limitation of a wideband signal analyser when it is compared to a spectrum analyser. So you are unlikely to find this stuff described in the marketing literature.

--- End quote ---

The SFDR within the analysis bandwidth is actually the third "key fact" in our FSW marketing brochure (see attached) :)

https://scdn.rohde-schwarz.com/ur/pws/dl_downloads/pdm/cl_brochures_and_datasheets/product_brochure/5215_6749_12/FSW_bro_en_5215-6749-12_v1600.pdf

I made an entire video explaining dynamic range (and SFDR) in spectrum analyzers because we absolutely want people to understand this specification :)



--- End quote ---

Thanks. If you now apply your SFDR definition in the video at 6:45 to your signal analysers, what SFDR do they achieve when set to their widest analysis bandwidth option when used on the upper bands of the analyser? That is the point I’m trying to make.

This is when the analyser downconverts to a low first IF rather than upconverts to a high IF.

When a wide analysis bandwidth is selected, many signal analysers have to turn off the narrow YIG preselection in this usage case and this destroys the SFDR. Usually, the manufacturer buries this SFDR limitation in the datasheet and they don’t make it obvious that the SFDR collapses without the YIG preselector. It’s up to the reader of the datasheet to understand the implication that the SFDR collapses when the widest analysis bandwidths are selected.

The true SFDR of an analyser includes all spurious responses including image responses and IF responses.
G0HZU:
Another way to look at it is that a typical ‘wide IF’ signal analyser often loses its integrity as a spectrum analyser when set to its full analysis bandwidth. Once the YIG filter is deselected, you may find the image rejection collapses to almost nothing and the IF rejection might only be 30dB.
The bandwidth of the YIG filter is typically less than the analysis bandwidth so it has to be deselected.

Manufacturers of signal analysers tend to make this information as obscure as possible, often only describing the SFDR when the YIG is selected. It’s up to the reader of the datasheet to understand that the SFDR collapses without the YIG preselection. The YIG filter is quite narrow and it also introduces group delay and so it often has to be deselected by the operator as it can mess up the performance when analysing modern wideband digital signals for things like EVM.



pdenisowski:

--- Quote from: G0HZU on June 05, 2024, 07:30:12 am ---Thanks. If you now apply your SFDR definition in the video at 6:45 to your signal analysers, what SFDR do they achieve when set to their widest analysis bandwidth option when used on the upper bands of the analyser? That is the point I’m trying to make.

--- End quote ---

And it is an excellent point :)  You're absolutely right about the challenges involved with SFDR in the scenarios you describe.


--- Quote from: G0HZU on June 05, 2024, 07:30:12 am ---it can mess up the performance when analysing modern wideband digital signals for things like EVM.

--- End quote ---

And yes, EVM performance has become one of, if not the, key performance parameters on the high-end for spectrum analyzers.  We put together an entire webinar series on EVM because it's such an important measurement these days (5G NR, newer "flavors" of 802.11, etc.)

https://tinyurl.com/mr3htv58

I'll ping our EVM expert today and ask him about how we spec SFDR at different BWs, frequencies, etc.

Note to @2X : sorry for the digression - none of this applies to the FPC since it doesn't do vector analysis :)
2X:
Many thanks to all fo you for your replies. Indeed in R&S channel there is plenty of good videos.

 

Navigation
Message Index
Previous page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod