On 03/04/2013 11:02 AM, Poul-Henning Kamp wrote:
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In message<4056222B698D4625893194A1E3AD4144@athlon>, "Ulrich Bangert" writes:
given the fact that the measurement results of a 5370 are integer multiples
of 20 ps [...]
Once you get to this level of detail, it is important to know that the
actual number is not 20ps but 19.5763ps
See page 8-19 in the manual.
Since we are in nit-picking mode, on page 8-29 it says the resolution is
in 5/256 ns, which I get into 19,53125 ps (exact).
One way to understand this is that the gearbox of the 5370B
interpolators creates a virtual clock of 51,2 GHz. Not bad for a core
design in 200 MHz and some smart ECL logic from late 1970thies.
Sufficient trigger noise (~ 8 ps) will smooth out the quantization, just
as Bruce mentions. This interpolation trick was used in the 5328A with
suitable option in the TI mode. It's good for TI/freq/period averages,
but not for their stability measures (unless compensated for).
Sufficiently low slew-rate can thus "improve" the result. :)
Cheers,
Magnus
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