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REVIEW - Rigol DS2072 - First Impressions of the DS2000 series from Rigol
zibadun:
--- Quote from: marmad on July 13, 2013, 02:37:40 am ---
I found Agilent's Patent for the (original) technique - filed in 1991, and invented by Matthew S. Holcomb of the Hewlett-Packard Company. Pretty interesting... I've attached a few images from the Patent here.
Edit: Here is also another published paper about the technique.
From the paper:
"Instead of storing every Nth digitized point, the decimator can be designed to randomly select one out of every N points for storage. In the case of the 10.01-MHz input, the points placed in memory are points randomly selected from the ten cycles of the input that occur in every 1-s interval. This random sample selection technique effectively dithers the acquisition clock during the acquisition and prevents a beat frequency from developing.
This intra-acquisition dithering technique has been used throughout the HP546XX oscilloscope product line and again in the HP54645A/D products. The effect it has on aliasing is dramatic. Fig. 7a shows the aliased 10-kHz sine wave that is produced when a 10.01-MHz sine wave is sampled at 1 MSa/s. Fig. 7b shows the same display using the dithering process just described. The resulting display is a fuzzy band much like what would be seem on an analog oscilloscope, with all signs of an aliased waveform removed."
Edit2 @zibadun: So... still think 'my special method' is a gimmick? :) Apparently, it works quite well eliminating aliases, doesn't affect interpolation, and the reason there isn't lots of information about it in DSO literature is because HP patented it and Agilent doesn't seem to want to talk about it - instead using terminology like the following from the 5000/6000/7000 Series Oscilloscopes User’s Guide:
"At slower sweep speeds, the sample rate is reduced and a proprietary display algorithm is used to minimize the likelihood of aliasing."
--- End quote ---
Good research, marmad. So if Rigol does this they would need a license from hp/Agilent?
Btw my comment was about SDR receivers, which use a different method to decimate raw adc samples. It may be as good or better than hp's (for example they reduce broadband noise while down converting instead of adding it)
high performance FPGAs were not so common in 91 so may be this was the best hp could do. Time to move on? :)
Wim13:
FFT and aliasing, ( two topics in one )
@Teneyes,
I can not find in the topics here the effect of turning aliasing on in FFT, you get then double
See picture 1, aliasing off, 25 Mhz per div
See picture 2,aliasing on, 50 Mhz per div
Also the picture shape is totaly different, when off and on
I always usse alias ON on FFT, because thats is more the way it should be..
( @Marmad, in RUU, if there is a space(s) behind the TCPIP srting, it wont connect )
marmad:
--- Quote from: zibadun on July 13, 2013, 03:27:35 pm ---Good research, marmad. So if Rigol does this they would need a license from hp/Agilent?
--- End quote ---
I was wondering the same thing myself. I wouldn't normally expect Rigol (or any Chinese Co.) to worry about licenses - but since they had (have?) a working relationship with Agilent, perhaps that makes a difference. It's such a simple technique - and easy to implement in software. IMO, a very clever idea by Matt Holcomb.
--- Quote ---high performance FPGAs were not so common in 91 so may be this was the best hp could do. Time to move on? :)
--- End quote ---
I don't know. It adds ZERO overhead (at least if down while sampling) - and Agilent has built this into their latest MegaZoom silicon. So I suspect they haven't discovered anything that is as fast and effective.
marmad:
--- Quote from: Wim13 on July 13, 2013, 04:09:25 pm ---( @Marmad, in RUU, if there is a space(s) behind the TCPIP srting, it wont connect )
--- End quote ---
There shouldn't be - the last that I heard about it was that it was working over LAN.
Wim13:
--- Quote from: marmad on July 13, 2013, 04:50:35 pm ---
--- Quote from: Wim13 on July 13, 2013, 04:09:25 pm ---( @Marmad, in RUU, if there is a space(s) behind the TCPIP srting, it wont connect )
--- End quote ---
There shouldn't be - the last that I heard about it was that it was working over LAN.
--- End quote ---
Work fine over LAN, very good, but the first time i would not connect, then
i saw that Windows copy and paste, did a extra space at the end at: TCPIP::192.168.2.36::INSTR
But with that extra space it cannot connect. maybe you can remove spaces.
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