[time-nuts] A little report from EFTF-IFCS 2022

[Magnus Danielson]

Fellow time-nuts,

I thought I would drop a few notes of high-light from the EFTF-IFCS 2022 
conference in Paris that ended yesterday.

It has been an intense week for those of us attending. Turns out there 
where more fellow time-nuts there than what made them selfes know when 
asked beforehand on the list. We have a few lurkers out there. Which is 
nice anyway.

Several of the tutorials was really good, such as the "Allan deviation 
and friends" of François Vernotte, "Satellite Time-Transfer" of Pascale 
Defraignes and also the one on optical frequency transfer.

 From NIST there was a presentation on a 30 GHz divide by 3 
re-generative divider. That turned out to be really interesting talk at 
Archita Hati told the story of the many steps and iterations that went 
into it and showed many phase noise plots on the way. From the 
commercial test-board (for a 0.5-40 GHz divider) to the many steps of 
making improvements. She ended up building new amplifiers that brought 4 
amplifiers in parallel to lower the flicker noise. A flip of the initial 
mixer (that takes 30 GHz input and 10 GHz output and produces a 20 GHz) 
allowed the limited bandwidth of the LO port to remove the sum frequency 
(40 GHz) rather than taking a loss in a separate filter. Really 
impressive performance. It failed to start despite Barkhausen conditions 
to be there, so the digital divider solution was used to inject a 
boot-strap 10 GHz for a short while and then remove it and it would go 
into it's low-noise mode.

Another interesting presentation was from JHU APL on a early development 
on their Ultra Stable Oscillator, where they wanted to reduce the size 
and weight by removing thermal isolation material. What they did was 
they put temperature sensors around the crystal and then added the basic 
ovenizing drive. They then used a DDS to correct the output and trained 
a shallow AI system to provide the correction steering. It showed some 
impressive early results.

Both of these two talks I was fortunate enough to have in the session I 
chaired.

One session and also a poster which was interesting was on the 
redefinition of the SI second. Essentially three options have been 
considered 1) Select one species 2) Use an ensamble of species or 3) 
Alter some natural constant. It has now been concluded that the later is 
impractical, as there is no single constant that fit the bill. So, 
therefore either selecting one species or doing ensamble of them 
remains. I think the ensamble approach is best in the long run, as it 
allows a richness of measurements to improve the precission as we go.

There where talks about MEMS that shown that it has started to mature 
more and more. Many lessons learned.

There where talks about miniatured atomic clocks, and things progress 
nicely there. Low-noise version of CSAC for instance.

One poster of Pascale Defraignes was very interesting, as it was on 
improved measurement on Beido results in R2CGGTSS and it turns out that 
there are offsets between new and old system. Turns out that there is 
also offsets between different GPS satellites that needs to be 
calibrated. Calibration of receivers becomes harder and harder as you 
aim towards low offsets.

While for sure not complete, these are some of the things that at least 
I got impression of. I am sure others have their impressions to share.

Lots of friendly faces, some new faces.

Next years conference will be in Japan. We where told that the 
Shinkansen train from Tokyo airport takes 2 hours and 8 minutes. I will 
have to protect that part of the calender already now.

Cheers,
Magnus