Equivalent time sampling
in [DSP]
|
Prev: MPEG-Xtreme
Next: Complex Input
From: alexgaas on 5 Nov 2009 12:54 Hi guys! Does anyone know any algorithm used in digital storage oscilloscope? I know that many DSOs use equivalent time sampling technique but what about the digital hardware (or algorithms) to filter and reconstruct the signal?? If anyone knows some papers (IEEE or other) let me know! Thanks a lot!
From: Jerry Avins on 5 Nov 2009 13:13 alexgaas wrote: > Hi guys! > Does anyone know any algorithm used in digital storage oscilloscope? > I know that many DSOs use equivalent time sampling technique but what > about the digital hardware (or algorithms) to filter and reconstruct the > signal?? > If anyone knows some papers (IEEE or other) let me know! > Thanks a lot! Time sampling equivalent to what? You might get help if we know what you want to do. Basically, one samples the waveform and puts the points into memory, then displays the points repeatedly. Lo sample rates can capture fast repetitive signals by sampling points on successive cycles. e.g.: capture a 10-point display by sampling a1, a8, b5, c2, c9, d6, e3, f0, f7, g4. The letters represent the cycle, while the numbers represent the sample positions within a cycle. When the samples are displayed 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 a picture of one cycle emerges. Although the sample rate can be low, the aperture time must be small. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
From: cassiope on 6 Nov 2009 12:05 On Nov 5, 9:54 am, "alexgaas" <alex_g...(a)hotmail.com> wrote: > Hi guys! > Does anyone know any algorithm used in digital storage oscilloscope? > I know that many DSOs use equivalent time sampling technique but what > about the digital hardware (or algorithms) to filter and reconstruct the > signal?? > If anyone knows some papers (IEEE or other) let me know! > Thanks a lot! Jerry has explained something of the time sequencing used in equivalent time scopes. It might also be useful to consider a frequency-domain explanation: that equivalent time scope make a practical use of frequency aliasing - deliberately shifting high frequencies into much lower frequencies by careful undersampling. The technique has been used for decades - long predating DSOs - and are probably mostly corporation-internal, so (guessing here) may not exist in the "current" literature. You'll probably have to scour the IRE transactions and the like to get something approaching what you're looking for. Though it might be in some trade rag in some form. HTH!
From: Phil O. Sopher on 6 Nov 2009 12:24 "cassiope" <fpm(a)u.washington.edu> wrote in message news:8c27729f-052b-4800-bfae-842e04c75010(a)d9g2000prh.googlegroups.com... > It might also be useful to consider a frequency-domain explanation: > that equivalent > time scope make a practical use of frequency aliasing - deliberately > shifting high > frequencies into much lower frequencies by careful undersampling. ISTR playing with a sampling scope in 1972 which, if I recall correctly, included caveats in the "destructions" about deliberately and manually varying the sampling rate to check that aliasing effects were not being observed.
From: Jerry Avins on 6 Nov 2009 13:31 cassiope wrote: > On Nov 5, 9:54 am, "alexgaas" <alex_g...(a)hotmail.com> wrote: >> Hi guys! >> Does anyone know any algorithm used in digital storage oscilloscope? >> I know that many DSOs use equivalent time sampling technique but what >> about the digital hardware (or algorithms) to filter and reconstruct the >> signal?? >> If anyone knows some papers (IEEE or other) let me know! >> Thanks a lot! > > Jerry has explained something of the time sequencing used in > equivalent time scopes. > It might also be useful to consider a frequency-domain explanation: > that equivalent > time scope make a practical use of frequency aliasing - deliberately > shifting high > frequencies into much lower frequencies by careful undersampling. > > The technique has been used for decades - long predating DSOs - and > are > probably mostly corporation-internal, so (guessing here) may not exist > in the "current" literature. You'll probably have to scour the IRE > transactions and the > like to get something approaching what you're looking for. Though it > might be in some > trade rag in some form. A historical note: The technique was invented at RCA Laboratories by Juan Amodei sometime around 1960. The first neat implementation was a plugin for a Tektronix scope; Juan showed me how to use it. The patent rights were sold to Tektronix, so they were the first commercial producer. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
|
Pages: 1 Prev: MPEG-Xtreme Next: Complex Input |