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Pocket-Sized 6 GHz 1 TS/s ET Scope
SJL-Instruments:
--- Quote from: joeqsmith on March 04, 2024, 06:03:28 pm ---From what I can tell, the latest manual makes no mention of this.
So, if CDF(0) > CDF(1), both CDF(0 &1) are set to the average of CDF (0&1). We then check the new value of CDF(1) with CDF(2). Once all are checked, we repeat this entire process until they are in order. Then we calculate the new PDF.
--- End quote ---
Yes, that's correct. We'll document this in the next manual revision. If you want it to converge faster, you can overcompensate slightly: set CDF(0) to (average - delta) and CDF(1) to (average + delta) where delta is some fraction of CDF(0) - CDF(1).
Essentially you're just removing all of the negative probability densities in the PDF in the minimally invasive way.
joeqsmith:
Shown using the same setup as previous plot with your software. For those wanting to try their own thing, attached Zip contains CSV file for the voltage and CDF pairs.
--- Quote ---...where delta is some fraction of CDF(0) - CDF(1).
--- End quote ---
Interesting is how much of a difference using 50% vs 40% vs 30% makes in how well it de-speckles.
PHOStronics:
Is the reason the monotonicity constraint is not directly part of the gausian process regression just implementation complexity, or is there a reason not to do it?
You mentioned you enforce it only in post processing but that seems like something that would aid in reducing the space of possible functions, and thereby alter the actual amount of information potentially gained from a trial voltage chosen
SJL-Instruments:
--- Quote from: PHOStronics on March 06, 2024, 06:02:29 pm ---Is the reason the monotonicity constraint is not directly part of the gausian process regression just implementation complexity, or is there a reason not to do it?
You mentioned you enforce it only in post processing but that seems like something that would aid in reducing the space of possible functions, and thereby alter the actual amount of information potentially gained from a trial voltage chosen
--- End quote ---
The monotonicity violations are just a result of the inherent statistical noise during sampling and are unrelated to the choice of query voltages. The monotonicity condition applies only to the "true" CDF values and not to the sampled CDF values, so you cannot assume this during acquisition.
joeqsmith:
Sorry about the long delay but finally rebuilt the FPGA to further even out the distribution so we can see all of the level state changes. Showing with 40k trigger min/max PAM4 with brightness set to max and something reasonable. Zoomed into the transition area. This was after a few hours of warmup. At 128 pts/div, it took several minutes to collect this data and initially the drift was really messing with the measurements. Big improvement in the noise but is it ever slow.
I tried several approaches to further reduce the speckles. I mentioned looking at the histograms and doing a window. One used a weighted filter. Then there was a modified conways life sort of technique. They all of course strip out good data. Looking forward to the new firmware.
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