> Fine adjustment of SAWG f0 by RTIO and local DSP is the planned path
> for dynamically compensating for time-variation of the Coherent
> Paladin laser repetition rate. Could the resolution of the the f0 NCO
> be defined parametrically? This could enable relatively
> straightforward switching between faster compile times and finer
> resolution.
Can't you do that equally well by adjusting the frequencies of the baseband
oscillators while holding the DUC frequency fixed (assuming the drifts are
small compared with the RTIO frequency)?
My view is that we shouldn't give up the flexibility of being able to fine-tune
the DUC frequency unless there is a good reason to do so. For example: if the
complexity/compile times of the current code make development/maintenance
problematic(*), or if the current code is going to have issues achieving the
full 1GSPS data rate. It would be good to hear a bit more from SB/RJ on the
advantages of moving to a simpler DUC parametrization.
(*) this was certainly the case in the early days of Sayma where the board
behaved differently when replacing the SAWG with a dummy ramp generator.
Thankfully now the PI issues that caused that have been fixed, it seems that
all non-SAWG related issues can be debugged without compiling the SAWG, so this
may be less of an issue...
Dr Thomas Harty
Junior Research Fellow, St John's College
University of Oxford, Department of Physics
The Clarendon Laboratory
Parks Road, Oxford, OX1 3PU
Mob: +44 (0)7986 375 052
Lab: +44 (0)1865 272 572
From: Joe Britton
Sent: 10 July 2018 21:37:31
To: Thomas Harty
Cc: artiq@lists.m-labs.hk
Subject: Re: [ARTIQ] ARTIQ Digest, Vol 50, Issue 2
> It would be good to get the interpolation running, both to improve spectral
> purity and to put the hardware through its paces before we move on to the
> next design revision (I'd love to see synchronisation at max DAC clock
> rate).
I agree with @hartytp on this. Pushing digitization artifacts to
higher frequencies is really helpful.
>> drastically reduce the SAWG digital upconverter resolution to a few
>> frequencies (use the other NCOs to for fine tuning).
Fine adjustment of SAWG f0 by RTIO and local DSP is the planned path
for dynamically compensating for time-variation of the Coherent
Paladin laser repetition rate. Could the resolution of the the f0 NCO
be defined parametrically? This could enable relatively
straightforward switching between faster compile times and finer
resolution.
> - f_RTIO = 125MHz
> - f_DAC = 2GHz
> - f_data = 1GSPS (2 x interpolation)
These parameters are fine for the UMD-Duke-ARL application set. -Joe
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