Educate myself on spectrum analyzers

[Wuerstchenhund]

Just to be fair, i know that chinese b-brands usually are what they are in terms of quality and documentation, which are both of extreme importance, but i wouldn't automatiacally rule them out..

I wouldn't rule them out, if it was for hobby use. B-brands are perfectly fine for that.

For business use however, they aren't really worth the money, and can quickly cost you a lot more during their lifetime than what you saved with the initial purchase price.

look at siglent: siglent designs and rebrands for many others and those products are still well built, good quality instruments.. maybe not the best, but not as bad as you would think if they didn't have the shiny name.

Yes, Siglent scopes are rebranded by many other brands, but most of them are B-brands that have no own hardware design/production facilities, and often a reputation that is even worse than Siglent.

The only big brand that rebadges Siglent scopes is LeCroy which buys Siglent SDS1000CML/CFL scopes and SDG1000 and SDG5000 AWGs and resells them as WaveAce and WaveStation, and these rebadges have already lead to very negative customer feedback because the previous models (WaveAce 100/200) were increadibly buggy, and because Siglent was unable to fix the bugs in a timely manner LeCroy had to take back lots of them, which didn't really help their reputation. The current Siglent rebadge scopes LeCroy offers are a bit better and less buggy because LeCroy now pushes Siglent much harder to get things in order, but there are all the other Siglent products where no-one pushes them for fixing bugs, which is why we have things like the SDS2000 debacle.

The only really good Siglent scope is the SDS3000 which outside China is sold by LeCroy as WaveSurfer 3000, and which has been developed with leCroy support on the hardware side and where Siglent is kept off the software (which comes directly from LeCroy). The result is a great scope, at the moment probably the best in its class. And it's fully supported by LeCroy like any other LeCroy scope.

But that doesn't makes other Siglent products any better. You still get a product with decent hardware, bug-ridden software written by people who have no idea how software development should work, a complete lack of proper maintenance documentation and poor product support.

If you can live with hobby-grade equipment in your business be my guest.

[G0HZU]

That is true, at least to some extend, but you're completely missing the point, which is that even the 90 pages in the Agilent AN150 aren't really a lot for such a complex topic, and I really would have expected you being able to appreciate that a 200+ page document about a certain topic is more likely to go into more details than a 90 page or even 50 page app note.

I certainly didn't suggest to not read the AN150s, so no need to become so defensive.

I'm defending the AN150 series because you appeared to dismiss it in your earlier post.

but if you're looking for something that pretty much starts from Adam and Eve then ANs are the wrong type of document.

For many people these documents do start at the very beginning. I really don't think you have read the full series of these documents because you would realise that AN150 wasn't just one document that got revised over the years.

If you don't believe me then look at the version of AN150 that is dedicated to measuring classic AM and FM waveforms with a spectrum analyser.

Then compare what your R&S book says on these subjects. (close to nothing)

Try the same with pulsed modulation. The AN150 dedicated to measuring pulsed modulation is a classic document probably studied by many thousands of engineers. The version I read at work is probably 40 years old now.

We had the whole AN150 series from HP and each one was in a coloured booklet. There were about a dozen different AN150 documents each covering a specialist subject to do with making better measurements with a spectrum analyser. eg one AN150 for tracking gen use, one for external mixer use, noise measurements, distortion etc etc.

I really would have expected you being able to appreciate that a 200+ page document about a certain topic is more likely to go into more details than a 90 page or even 50 page app note.

That is you in a nutshell. You judge things by numbers.

I don't know or care how many pages there are in all of the AN150-x series if you totalled it all up. These are classic documents. Not everyone will want to read them because some are so old now and the content doesn't cover analysers with a digital IF. But the newer docs from Agilent do. They probably attach AN150 to some of them out of sentimentality but the newer versions of AN150 aren't meant to replace the whole classic series.

But I will repeat again that for a beginner you can't beat having a decent tutor to talk you through this stuff with you both in front of a suite of real test gear. The app notes and books aren't enough on their own. They try to cater for all needs/abilities from hobbyist through basic technician through to engineering level. This will probably make the material appear quite daunting for some people unless you have a tutor to help.

[Wuerstchenhund]

I'm defending the AN150 series because you appeared to dismiss it in your earlier post.

I did not dismiss them, so please keep your biting reflex under control.

but if you're looking for something that pretty much starts from Adam and Eve then ANs are the wrong type of document.

For many people these documents do start at the very beginning.

For many engineers at the beginning is an education in basic RF principles, without you will have a very hard time understanding what the HP AN's are telling you.

I really don't think you have read the full series of these documents because you would realise that AN150 wasn't just one document that got revised over the years.

Yeah, this is why I wrote that I read the Series  Oh well...

And because I read them I do know that, while the HP ANs were great resources most engineers kept for later reference (I also did back then), they were still Application Notes, i.e. with a somewhat limited depth (many topics discussed in the various ANs could easily fill a book). Which made them ideal for quick referencing. There's also the fact that the AN150s weren't really updated and while the general principles remain true, also contain outdated information.

And because I read them I also know that Agilent later decided to make ANs more 'appealing' to a wider audience, so AN150 went from a Series of different topics to become a simple overview about Spectrum Analysis. And that overview is the one you linked:

http://cp.literature.agilent.com/litweb/pdf/5952-0292.pdf

and that is pretty much the same as the R&S SA Primer I linked earlier.

If you don't believe me then look at the version of AN150 that is dedicated to measuring classic AM and FM waveforms with a spectrum analyser.

Then compare what your R&S book says on these subjects. (close to nothing)

Try the same with pulsed modulation.

Sure. Now tell me, which of the old AN150's talk about FFT or signal processing? It's been a while since I went through the HP ones but I can't remember any that discuss such topics, aside from the small section in Agilent's/Keysight's modernized variant.

The AN150 dedicated to measuring pulsed modulation is a classic document probably studied by many thousands of engineers.

That may well be true but it certainly isn't the only document.

Besides, I'm not saying the old AN150s shouldn't be read (which is what you seem to imply). I'm saying they aren't the best start if you want to get a start into Spectrum Analysis (the topic of this thread, remember?). The new AN150 and the R&S Primer are better suited for that, but both contain less information than the book I pointed to.

[G0HZU]

Besides, I'm not saying the old AN150s shouldn't be read (which is what you seem to imply). I'm saying they aren't the best start if you want to get a start into Spectrum Analysis (the topic of this thread, remember?). The new AN150 and the R&S Primer are better suited for that, but both contain less information than the book I pointed to.

The R&S book you linked to is fine but you don't seem to grasp that AN150 is aimed at the customer and it tries to cover classic topics relevant to the customer and it tries to deliver this information in a way that has the best chance of helping customers across all skill levels.

So there are documents devoted to AM and FM modulation. Also a very useful document on making field strength measurements. The R&S book doesn't cover practical stuff like this. It does cover pulse modulation but I would suggest that the AN150 document on pulse modulation is written better (as in it will appeal to users on multiple skill levels), and it has more equations and more plots despite being 40 years old.

Do you see the difference now? I'm not dismissing the R&S book, I think it is a good book but it doesn't replace AN150 in the way you imply. Note that I'm not suggesting that AN150 replaces the R&S book either.

There are other Agilent app/product notes aimed at advanced use of a modern spectrum analyser but they don't carry the AN150 logo any more. These app notes are aimed at advanced users and focus on specific issues and limitations in a modern spectrum analyser.

I can post up these notes but (according to your reasoning) these can't possibly go into as much detail as the R&S book because the R&S book has more pages than any individual app note and an application note is 'just' an application note =AN  and not a 'deep' book with 200 pages

[G0HZU]

G0HZU: For many people these AN150 documents do start at the very beginning.

Wuerst: For many engineers at the beginning is an education in basic RF principles, without you will have a very hard time understanding what the HP AN's are telling you.

Just start at the BEGINNING and read the raw AN150 from >40 years ago. I found a familiar version here:

http://hpmemoryproject.org/an/pdf/an_150.pdf

It is incredibly dated now but I'm still not aware of anything that introduces the concept of the swept superhet spectrum analyser as elegantly as this app note. It's a wonderfully written introduction aimed at the novice user. The 'Adam and Eve' stuff about the obsolete 'swept tuned analyser' and the clunky old 'real time system' adds value because it helps show the reader the benefits (and some limitations) of the classic superhet topology used in modern analysers.

I'm not sure it can get any more basic than this...It had to be basic back in those days because the vast majority of (potential) customers would have been novices themselves even if they were fully qualified EEs.

Today, it's different because so many people are familiar with spectrum analysis and so some of the stuff in that early AN150 doc will only be necessary for the complete novice. But there are loads more AN150 docs to choose from covering lots of topics.


Here's one covering AM and FM modulation. It's very old but some of the theory is timeless anyway.
http://hpmemoryproject.org/an/pdf/an_150-1a.pdf

Here's the one discussing measurements of pulsed signals with a gradual introduction to the more detailed stuff:

http://hpmemoryproject.org/an/pdf/an_150-2.pdf

Wonderful stuff... the author uses lots of text and diagrams with only the basic equations until the later sections. written in 1971!


Here's the one on making basic field strength measurements with a spectrum analyser.

http://hpmemoryproject.org/an/pdf/an_150-10.pdf

It's short but it is packed with basic theory. It lacks some stuff to do with modern EMC measurements (eg quasi peak measurements etc) but is still worth a read for some people who maybe want to do a bit more than just blindly play with crude sniffer antennas.

Sure. Now tell me, which of the old AN150's talk about FFT or signal processing? It's been a while since I went through the HP ones but I can't remember any that discuss such topics, aside from the small section in Agilent's/Keysight's modernized variant.

Those old AN150s are over 40 years old. What did you expect to see? The DSP/FFT stuff didn't begin to appear in the mainstream GHz analysers until the later models like the classic HP8566B and HP8568B. These classic high end analysers were deep in development at around the same time the early AN150s were being released but not on sale for a few more years. There are newer app notes available that cover today's generation of analysers with a digital IF.

Eg see this AN150 from 2004. It's only a basic introduction to a vector signal analyser with a digital IF but I'm not sure if you will complain (again) and criticise it for being too simple or too difficult for non EEs. You seem to be difficult to please...

http://www.hpmemoryproject.org/an/pdf/an_150-15.pdf

[G0HZU]

Here's a complete? list of HP application notes released over the years.

This stuff was like 'porn in the mail' to an RF engineer in the days before the internet. There's lots of good stuff here.

Make sure you scroll down to find the complete list as the first list you see are just recent additions that have been added.

http://www.hpmemoryproject.org/ressources/resrc_an_01.htm#

The AN57-x is a good series of documents on noise figure measurements using a spectrum analyser. Definitely worth reading!
If you want to create some software or a spreadsheet to handle all the calculations to do this stuff yourself  then I recommend reading this app note from R&S.

https://cdn.rohde-schwarz.com/pws/dl_downloads/dl_application/application_notes/1ma178/1MA178_2e_NoiseFigure.pdf

This gives worked examples which will help prove/troubleshoot these tricky equations. I used a similar app note from R&S a few years back when I wrote some software to use with my hot/cold noise source and spectrum analyser here at home. The worked examples are very useful!

[Wuerstchenhund]

I'm certainly not addressing every point as it would be useless, as I'm not disagreeing with you in the way you seem to believe.

I'm not dismissing the R&S book, I think it is a good book but it doesn't replace AN150 in the way you imply.

I never said the book replaces AN150, that is just in your head. All I said is that the book is a better start (i.e. beginning where to read) for someone wanting to learn more about spectrum analysis. There's nothing wrong with the AN150, and I'd certainly recommend reading them, but I don't believe they are a particularly great first start.

[/quote]Note that I'm not suggesting that AN150 replaces the R&S book either.[/quote]

Fine. But then I never assumed you did.

I told you, keep that biting reflex in check

[pascal_sweden]

Maybe the best thing is, to just read both documents. Problem solved. No discussions anymore.

Both Wuerstchenhund Ltd. and All The Others Company are happy

[4cx10000]

Maybe the best thing is, to just read both documents. Problem solved. No discussions anymore.

Both Wuerstchenhund Ltd. and All The Others Company are happy

Excellent idea!!   

[Wuerstchenhund]

Maybe the best thing is, to just read both documents. Problem solved. No discussions anymore.

Both Wuerstchenhund Ltd. and All The Others Company are happy

Read everything you can get your hands on. Seriously! Especially when it comes to complex topics, you will often find some interesting details even in overall poor documents.

As I said it before, my recommendation is to *start* with the R&S book, simply because I think it makes a very good entry into the topic (and when I was still teaching most of my students agreed that its a good starting point, so there's some basis to my assumption). But that's merely a starting point, not the end of the journey.

[G0HZU]

Maybe the best thing is, to just read both documents. Problem solved. No discussions anymore.

Both Wuerstchenhund Ltd. and All The Others Company are happy

Yep, maybe we should simply redress the balance and allow me to highlight a few limitations wrt the R&S book and let the reader decide if it 'deeply' covers everything they might want to know about spectrum analysers. (as per the title of the thread)

So having skimmed through the R&S book I'll say this:

If you want to understand the history and architecture of spectrum analysers throughout the last 50 years right up to today then the R&S book is very weak on this.

If you JUST want to see how a modern vector signal analyser works (these are the spectrum analysers and SDRs of TODAY) then don't read the R&S book. (you can try but you won't find anything but have a look at AN150-15 from HP instead)

http://cp.literature.agilent.com/litweb/pdf/5989-1121EN.pdf

If you want to read up on how to use a classic swept spectrum analyser to demodulate and display real world signals then the R&S book is the wrong book to use because it doesn't cover these topics in any detail. It doesn't even cover how to display or understand AM and FM signals. Try reading the relevant AN150-1a doc as a start.

If you want to read up on how the latest generation of vector analysers (or SDRs?) can demodulate analogue or digital signals in DSP then the R&S book is the wrong book to read. You can try but you won't find anything as it barely scratches the surface. But try reading the relevant (second) chapter of AN150-15 to see if it helps.
http://cp.literature.agilent.com/litweb/pdf/5989-1121EN.pdf

If you want to study spectrum analysers/analysis 'deeply' then the book from R&S is the wrong book because you can't cover this subject 'deeply' in just 200 pages using large fonts and big pictures and the presentation style of a typical degree thesis.

If you are just an average hobbyist with an average education and you are a novice wrt spectrum analysers then I think you will find the first 20 pages of the R&S book will shove a lot of equations and waveforms at you that you may find a bit daunting. The lack of pictures of what a spectrum analyser looks like, what basic things it can measure in these first few pages may surprise you.

The brief bit that covers FFT looks like something an inexperienced graduate would write. It's OK but it doesn't really deliver to the reader IMO. Contrast this to the wonderful writing style (and depth of content) in AN150-15 for example.

The section that does attempt to describe the basic  block diagram of a spectrum analyser is poorly presented and lacks detail and it doesn't flow well. Not enough pages, not enough background info compared to something like AN150.

The IF processing section is good with some useful stuff but the section on analogue/digital/FFT filters is quite basic/short. It's good stuff but it isn't 'deep' stuff.

The section on the various detector types is very short when compared to AN150 or other Agilent app notes. Again, not enough diagrams, not enough quality (or experience?) delivered from the text. It still would be OK for a lot of users but Wuerstchenhund promised us 'deep stuff' compared to an HP application note.

The section on 'overloading' and how  to prevent it is useful basic stuff and it's good to see it in the book. It's hard to describe this stuff adequately in text and pictures anyway. I would have preferred to see a two tone test used here though because it would show third order distortion effects at IF overload.

The phase noise section is fine/OK. The section on distortion is also OK and so is the section on dynamic range. None of it is special or deep though. The diagrams often look like they were created in a hurry and this lets down the presentation IMO.

The section on spurious levels is OK if a little short/basic but it simply doesn't have enough diagrams. This stuff was produced with a strict time budget IMO.

There's a detailed section on measurement uncertainty and you can tell that the author (finally) put some background effort into writing this. This section gives worked examples and it appears to be pretty good. I'd argue that it's out of balance with the rest of the book in this respect. However, the uncertainty analysis doesn't cover advanced material that you would find in a freebie product app note for a modern Agilent analyser.

The section on  pulsed signals is quite good and quite well presented. Again, it seems out of balance with the rest of the book in this respect.

This book is still a good book overall but it isn't the panacea that Wuerstchenhund paints it out to be. Large parts of it are presented like a typical degree thesis with only moderate chunks of text and just a few (or no) hastily prepared diagrams for each section. The section on 'detectors' is a good example of this.

The worst thing is that is doesn't deal with common modulation types and it doesn't describe or cover what can be done using today's vector signal/spectrum analysers or modern SDRs.

Put it another way... If I'd gone out and paid good money for this fairly brief book (decent technical books are not cheap) then I think I would be disappointed because this book is NOT a 'deep' book about spectrum analysis. It really does come across to me in a degree thesis style rather than any kind of reference book or font of knowledge/experience.