[time-nuts] Wavecrest DTS-2077 Teardown

[Magnus Danielson]

On 08/21/2013 03:51 AM, Ed Palmer wrote:
> Adrian,
>
> I used Timelab to assess the reaction of the DTS-2077 to different
> sine wave inputs.  The differences in the noise floor are surprising. 
> The attached picture was made by taking the output of an HP 8647A
> Synthesized Generator through a splitter, and then through different
> lengths of cables to the inputs of the DTS-2077.  The combination of
> splitter and cable loss meant I couldn't get +7 dbm @ 1 GHz.  If I
> could have, the 1 GHz line might have been lower than it was.
This is not very surprising. As you increase frequency, the slew-rate
changes, and as slewrate increases, it convert noise to jitter to a
lesser degree. Formula for slew-rate:

S = A*2*pi*f

where A is the amplitude and f is the frequency

Formula for jitter

T = e_n / S

where e_n is the noise RMS amplitude, S the slew-rate and T the timing
jitter RMS.

As you get closer to the instruments internal jitter, which forms a
floor, the increased slew-rate does not improve as quickly as you would
think.

Cheers,
Magnus