Source?NO source!,
I was leading you on,
I saved a waveform data ,
I then Patched the Data. to values to show a step change.
I then loaded it back into the DSO.
I thought everyone could see it was too prefect.
Square wave is series of sinewaves
Indeed.......with a fundamental, and upper and lower order harmonics....here are two plots with a higher interpolated sample rate.....one showing the dynamic fundamentals of the center frequencies and the other showing the total roll-off of those fundamentals....
I am a bit puzzled by the topic of "show us your square wave".....too many variables between the oscillator/gen and the scope reading.....I don't think it says a hell of a lot about the quality of a sig gen, without analyzing the entire signal path
I did the plots posted using coax (properly terminated), but the results will be completely different with a more stable probing solution....and different i/o & measurement settings......to have any kind of real meaning in reality, there has to be a standard/definition of measurement parameters....
maybe I am missing the point of the question?
How should these colors be interpreted - what do they signify or represent? Thanks
It's a great tool but for this specific exercise I don't think it adds any value, and since the scope was running in RIS (ETS) mode I'm not sure the waveform that is displayed has much to do with the input signal. The picture shows noticeable variations in the waveform, which means RIS is unsuitable here.
Square wave is series of sinewaves
Indeed.......with a fundamental, and upper and lower order harmonics....here are two plots with a higher interpolated sample rate.....one showing the dynamic fundamentals of the center frequencies and the other showing the total roll-off of those fundamentals....
I am a bit puzzled by the topic of "show us your square wave".....too many variables between the oscillator/gen and the scope reading.....I don't think it says a hell of a lot about the quality of a sig gen, without analyzing the entire signal path
I did the plots posted using coax (properly terminated), but the results will be completely different with a more stable probing solution....and different i/o & measurement settings......to have any kind of real meaning in reality, there has to be a standard/definition of measurement parameters....
maybe I am missing the point of the question?
A saw your post some time ago. You brought up some good points. You stated the DSO you used for this data was a WR64MXI with 600MHz BW with a 15MHz input using coax. I did not understand the THz FFT but thought I would try and replicate your results.
I am using my Sony AWG2041 to generate a 15MHz squareware with roughly the same amplitude as you show. This generator has a little sharper edges. I am using Thermax RGU-400 with SMAs torqued to 8"/lbs. ARB uses crappy BNCs, so I have a BNC to SMA for this test. My DSO is an older Wavemaster 8500A, 5GHz.
As I would expect, the FFT drops like a rock well before I reach 10G. Amazing how different the two setups behave.
kind of trying to re-enforce my earlier point, that showing square waves, even between "premium" gear is a rather pointless.....as it's very difficult to attribute exactly where the non linearities are coming from....are they induced (EM), are they processing "errors" etc etc etc....I could see one spending vast resources to produce a "perfect" square wave....only to realize it has no real practical application
it really is turtles all the way down
kind of trying to re-enforce my earlier point, that showing square waves, even between "premium" gear is a rather pointless.....as it's very difficult to attribute exactly where the non linearities are coming from....are they induced (EM), are they processing "errors" etc etc etc....I could see one spending vast resources to produce a "perfect" square wave....only to realize it has no real practical application
it really is turtles all the way down
Well, there is at least one turtle that benefits from a near perfect square wave source: Adjusting your high impedance HF probes as good as it gets
I see Rigol DSO displays are being posted on this thread and comments about overshoot.
It's a great tool but for this specific exercise I don't think it adds any value, and since the scope was running in RIS (ETS) mode I'm not sure the waveform that is displayed has much to do with the input signal. The picture shows noticeable variations in the waveform, which means RIS is unsuitable here.
It shows just how much the measurement device itself can influence the result....RIS + sinX interpolation + 3d persistence.....really shows just how many artifacts can be attributed to the WAY in which a device interpolates what it's being fed.....I wanted to show just how far away we can get from something "trustworthy", especially when sampling and interpolating a signal..
Producing a model of a square wave, should be a very straight forward endeavor.....but everything in between that model and the way it's interpolated to the screen of a discreet device makes the whole concept quite a bit more "complicated".....in the "analog world" we live in....square waves just don't seem to want to exist.....and nature seems to like to avoid straight lines....
YIKES!!!
That Rigol "25MHz square wave" is pretty useless.....I wonder just how bad the ds2000A-S gen is @ 15MHz. My plots showed some serious issues, but I assumed they were more related to cabling and the fact that the "specAN" in the MXi isn't a "real" discreet spectral analysis tool.....you don't happen to have a ds2000A-S in house do you?
YIKES!!!
That Rigol "25MHz square wave" is pretty useless.....I wonder just how bad the ds2000A-S gen is @ 15MHz. My plots showed some serious issues, but I assumed they were more related to cabling and the fact that the "specAN" in the MXi isn't a "real" discreet spectral analysis tool.....
you don't happen to have a ds2000A-S in house do you?
You have far nicer spectrum analyzer package than anything i have kicking around....
I know, but I thought I should highlight the RIS issue anyways to avoid that someone takes the screenshot too literally.
A perfect square wave can't exist, it's physically impossible as it assumes a indefinitely fast transition between low and high (which in this analog world is not possble). All we can get are more or less close approximations.
YIKES!!!
That Rigol "25MHz square wave" is pretty useless.....I wonder just how bad the ds2000A-S gen is @ 15MHz. My plots showed some serious issues, but I assumed they were more related to cabling and the fact that the "specAN" in the MXi isn't a "real" discreet spectral analysis tool.....you don't happen to have a ds2000A-S in house do you?
There are many more issues here, like PCB layout and PSU pulse response/decoupling at the output drivers. Capacitors and inductors are as always, everywhere and ring as they like.
My guess is running the built-in gen on the a-s at it's "limit" is producing useless data (in terms of analyzing the cabling and acquisition tool.
No, and what I've seen from Rigol so far nowadays I probably wouldn't touch another of their products with a bargepole. Admittedly some Rigol devices aren't as bad as say, Siglent, but after the DG1062z I've decided to stay with the big names.
Well, there is at least one turtle that benefits from a near perfect square wave source: Adjusting your high impedance HF probes as good as it gets