Agilent/Keysight scope bandwith specifications

[Keylectric]

Hi!

If memory serves me, in a PDF article Agisight mentioned this about gaussian vs maximally flat (or something like that) frequency response characteristics for digital scopes. Less than 1GHz bandwith often being gaussian with -3dB at typical specified bandwith. I also think I read about the use of DSP to straighten out the response that is displayed in some products (could have been some other brand though).

I have a DSOX3032 wich is supposed to have 350MHz bandwith but when looking in the calibration certificate document from the factory, that spec says -0.27dB and -0.32dB for channel 1 and 2 down at 350MHz  (200mV/div). The document mentioned -3dB as lower limit for that particular test.

I also looked at Daves video where he plays with the Jim Williams pulse generator, indicating that his 500MHz Agisight scope has a -3dB bandwith of 600-700MHz or so.

So, is this the norm or just random "overspecification"?

Maybe I actually have a 500MHz scope according to the usual way of specify?

Or did they forget to lock my scope to 350MHz.. the scope can be software upgraded to 500MHz (license key).

Happy measuring!

[Keylectric]

Maybe I picked the wrong name for the thread.. feel free to talk about specifications in general and how real spec relates to advertised.

[nctnico]

The actual bandwidth on an oscilloscope is usually better than specified. On my 200MHz Siglent SDS2000 the actual bandwidth exceeds 300MHz on every channel.

[Neganur]

IRRC the 350 MHz and 500 MHz 3000X scope have the same hardware so for me it boils down to that I have no idea how the software/option band limitation works.

Also, I don't know how strict you can be about the "3 dB" bandwidth nowadays. I imagine most modern scopes will have a similar response to what you see on your scope. And should you enter the 500 MHz option, the corresponding specs measured at 500 MHz will probably still be below 1 dB. So I would say that the manufacturer just built a good front end for the bandwidth he was targeting at. I wouldn't call it "overspecification" though, just better than spec.

[MarkL]

The Agilent/Keysight app note being referenced is probably this one:

  http://literature.cdn.keysight.com/litweb/pdf/5988-8008EN.pdf

And from the 3000X user manual (under "Oscilloscope Bandwidth and Sample Rate"):

Note that 1 GHz bandwidth 3000 X-Series oscilloscope models have more of a brick-wall type frequency response (also known a flat response) than the Gaussian response of lower bandwidth 3000 X-Series oscilloscope models.

[HighVoltage]

All my Agilent / Keysight scopes are exceeding their bandwidth, even the 1 GHz versions.
So, I think it is very "normal" that you see this on your scope.