[time-nuts] Odd-order multiplication of CMOS-output OCXO

[Mark Haun]

Hi Magnus,

On Sun, 19 Jan 2020 15:56:37 +0100
Magnus Danielson <magnus at rubidium.se> wrote:
> > I also found this common-base amp circuit in the archives:
> > https://www.febo.com/pipermail/time-nuts/2016-January/095683.html
> > and
> > https://www.febo.com/pipermail/time-nuts/attachments/20160126/ae3b4be8/attachment-0001.pdf
> >
> > I've read that I should avoid high-Q tuned circuits, because they
> > will introduce more noise with temperature variation.  Are there
> > any rules of thumb for how much Q is too much?  
> 
> You do not need very high Q, as suitable LCR will fit. Besides, if
> there is any of the other overtones creating issues, you can build
> LCR links tuned to these that will consume that energy.

Thanks, this makes sense.  Any general suggestions for the active
device selection, and circuit topology?  Is the common-base BJT circuit
(in the archive link) a good starting point?

> The other fairly obvious solution is as already suggested by Bert is
> to use a SiLabs chip.

I think Bert was referring to the ICS570 rather the the Si570.  The ICS
part would completely destroy the sub-picosecond jitter performance of
my oscillator (datasheet quotes jitter on the order of 100 ps!), so is
not an option.  The Si570 family is interesting.  I had another look at
the jitter / phase-noise specs and it probably would be good enough for
an 80-MSPS ADC.  However, I have other reasons (longer-term stability)
for wanting to use the OCXO.

> Regardless if which solution you try, what capability do you have to
> test it? It remains an important tool here. There is no golden design
> that just solves everything. I've recently measured how very well
> performing devices performance was partly lost due to bad design. I
> use the old and trusty TimePod.

Aha, this is the elephant in the room...  I will confess, I was hoping
for some rules of thumb that would give me 90% confidence without
having to validate the design.  (It's a hobby project, so a certain
amount of risk-taking is OK.)

The only time/freq stuff I have currently are a couple of HP 53310A
analyzers and a Trueposition GPSDO.  Putting together a DMTD setup
would be fun but my project queue is already overflowing :)

Regards,
Mark