Products > Test Equipment
Sub: Rigol's DHO800 Oscilloscope (Gibbs Effect & Aliasing Misunderstanding)
tautech:
Especially for Mech some screenshots better comparing apples.....at similar timebase settings....max on 1000X HD.
Bodnar powered from rear USB port. :P
X and SinC interpolation.... captured running and Stop.
Fungus:
--- Quote from: Mechatrommer on October 26, 2023, 07:15:38 pm ---i believe this is happening inside the dsp IC or fpga/asics, but that i cannot be sure, since i have no proof. its just highly likely, where else it can be? LC circuit cannot produce "non-causal" effect, can it?
--- End quote ---
I think it's this: https://en.wikipedia.org/wiki/Gibbs_phenomenon
It's counterintuitive that you see something before the pulse but it's mathematically correct. That's what you get when you apply a low pass filter to a discontinuity (step) in a signal.
ebastler:
--- Quote from: Fungus on October 26, 2023, 08:59:22 pm ---
--- Quote from: Mechatrommer on October 26, 2023, 07:15:38 pm ---i believe this is happening inside the dsp IC or fpga/asics, but that i cannot be sure, since i have no proof. its just highly likely, where else it can be? LC circuit cannot produce "non-causal" effect, can it?
--- End quote ---
I think it's this: https://en.wikipedia.org/wiki/Gibbs_phenomenon
--- End quote ---
It's sometimes advisable to read the next couple of posts before one fires off a reply. ;)
Fungus:
--- Quote from: ebastler on October 26, 2023, 09:05:27 pm ---It's sometimes advisable to read the next couple of posts before one fires off a reply. ;)
--- End quote ---
Yeah, I just noticed.
Still, nobody else posted a link to Wikipedia or said "if you apply a low pass filter to a step..." :-DD
Mechatrommer:
--- Quote from: Fungus on October 26, 2023, 08:59:22 pm ---
--- Quote from: Mechatrommer on October 26, 2023, 07:15:38 pm ---i believe this is happening inside the dsp IC or fpga/asics, but that i cannot be sure, since i have no proof. its just highly likely, where else it can be? LC circuit cannot produce "non-causal" effect, can it?
--- End quote ---
I think it's this: https://en.wikipedia.org/wiki/Gibbs_phenomenon
It's counterintuitive that you see something before the pulse but that's sin(x)/x for you.
--- End quote ---
yes i provided the link in my post. sin(x)/x is a highly theoritical and mathematical. iirc i read long ago that you cannot reconstruct back the sampled real signal back on monitor the way its appeared on electrical circuit if you dont do infinite terms reconstruction, at least thats what i understood. with limited terms, what you interpolated on screen will not match the real signal. even lesser terms, the displayed signal will be deviated even more from the actual one.
@tautech: refering to picture below. a little bit of "precursor" ringing could exist in real world i think to some specific semiconductors or logic fabrics? maybe something triggered inside the logic gate much earlier that caused ringing before actual logic state switch (rising and falling), but excessive precursor ringing is a bit unnatural, unnaturally "symmetrical" ;D. i wonder if such extreme such as image provided by 2N3055 just above could exist to physical/analog filter at dso front end. anyway, proofs that Loe's pulse doesnt have this excessive non-causality are already presented by other brands TE. fwiw.
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