Hi John,
On 08/31/2015 05:12 AM, John Miles wrote:
On that note, did you look more closely on the NIST analysis of
cross-correlation and a possible cancellation and thus overly optimistic
results? Did it have any consequence on your code? What did you take
away from it?
Yes, you can definitely get divots in the PN trace, especially in multiple-hour
runs needed to reach very low noise levels. I've seen that on occasion when
making measurements with independent downconverters. If the DUT signal
experiences significant phase shift in one downconverter path relative to the
other, I imagine that's a good way to provoke this behavior.
Fortunately I haven't run into any instances of the worst-case scenario
described in the Nelson paper, where the whole noise floor collapses without
any exhibiting any other weird artifacts. The phenomenon is certainly worth
keeping in mind but most people are not going to run into it, especially with
the Ch0 and Ch2 jumpers in place.
I'm the kind of guy that keeps those jumpers off and feeding three
signals, so that's why I am asking. :)
Cheers,
Magnus
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