[time-nuts] Best Chance GPS module

[André Esteves]

Millimeter accurate GPS in smartphones and self driving cars would
result from tiny atomic clocks
--

http://www.nextbigfuture.com/2016/11/millimeter-accurate-gps-in-smartphones.html
https://arxiv.org/abs/0707.4624

including energy harvesting, bio-sensing and quantum nanoelectronics.

They are producing designer endohedral fullerene molecules with
tailored electronic properties. Designer Carbon Materials Ltd is a
spin-out company from the University of Oxford. It is based on
research led by Dr Kyriakos Porfyrakis and his academic group of 9
researchers.

They have developed technology for the scaled-up production of
endohedral fullerenes. Our patented arc-reactor system can bring
endohedral metallofullerene production to the gram-scale and beyond,
faster and more efficiently than conventional arc reactors. They have
access to state-of-the-art facilities for the purification of a range
of fullerene molecules, including endohedral metallofullerenes and
endohedral nitrogen fullerenes.

Endohedral fullerenes, also called endofullerenes, are fullerenes that
have additional atoms, ions, or clusters enclosed within their inner
spheres. The first lanthanum C60 complex was synthesized in 1985 and
called La at C60.[2] The @ (at sign) in the name reflects the notion of a
small molecule trapped inside a shell. Two types of endohedral
complexes exist: endohedral metallofullerenes and non-metal doped
fullerenes.

Nitrogen endohedral fullerenes is being used to create a small and
portable atomic clock – the most accurate time-keeping system in the
world – and could make the GPS navigation on driverless cars accurate
to 1 millimeter.

"At the moment, atomic clocks are room-sized," said Lucius Cary, a
director of the Oxford Technology SEIS fund, which now holds a
minority stake. "This endohedral fullerene would make it work on a
chip that could go into your mobile phone.

In 2007, there was an arxiv paper which described the design of a
Micron-Scale Atomic Clock

Nitrogen atom is introduced into a fullerene cage. This endohedral
fullerene is then coated with an insulating shell and a number of them
are deposited as a thin layer on a silicon chip. Next to this layer a
GMR sensor is fabricated which is close to the endohedral fullerenes.
This GMR sensor measures oscillating magnetic fields on the order of
micro-gauss from the nuclear spins varying at the frequency of the
hyperfine transition (413 MHz frequency). Given the micron scale and
simplicity of this system only a few transistors are needed to control
the waveforms and to perform digital clocking. This new form of atomic
clock exhibits extremely low power (nano watts), high vibration and
shock resistance, stability on the order of 10^-9, and is compatible
with MEMS fabrication and chip integration. As GMR sensors continue to
improve in sensitivity the stability of this form of atomic clock will
increase proportionately.

It is possible to separate each endohedral fullerene from its
neighbors by coating it with a glass shell. Silica gel, an inorganic
polymer, has a three-dimensional network and can easily be synthesized
via the sol-gel route. Fullerenes cannot be incorporated into sol-gel
glasses homogeneously due to low solubility. This problem can be
overcome by functionalization of the fullerenes with such groups as
will form some kind of bond (hydrogen, van der Waals, or covalent)
with the growing silica network

The simple scheme discussed gives us a micron scale atomic clock with
10^−9 accuracy and a power dissipation of a nanowatt (10 nW capacitive
drive but we can use resonant circuits to store the energy). This will
likely be adequate for many mobile/sensor net applications but not
adequate for more demanding situations. What can be done?

First, as GMR sensors improve (BMR, etc.), we can use more diluted
fullerene stacks to gain a sharper line by a cubic factor in
separation as we lose an equal amount of magnetic signal. A
nanoscale-precise placing of fullerenes would give us a very well
determined perturbation situation that can be exploited for accuracy.
In the limit of true nanotechnology the ultimate clock is a single
fullerene with considerable shielding. This should be competitive with
very good atomic clocks of vastly more volume.

2016-11-30 21:36 GMT+00:00 Mark Sims <holrum at hotmail.com>:
> I have found that the cheap  V.KEL SIRF=III modules (I paid $15-$20 for three)  have excellent indoor performance with their built-in patch antenna.  They don't do GLONASS.  I even get indoor tracking with the module sitting on the ground floor of a 2 story hose with the patch antenna facing the floor!
>
> The NEO M8 is a decent device.  I've seen mine tracking over 24 sats.  The module that I have has a U.FL antenna connector with pads for adding an edge-launch SMA connector (I hate U.FL connectors).  I seem to remember that they can't track GPS, GLONASS, and BEIDOU at the same time.
>
> I have gotten surprisingly good performance with a cheap GPS/GLONASS puck like:
> http://www.ebay.com/itm/201698154683?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
>
> For NTP applications,  multi-path errors will be swamped out by the "noise" in NTP.  I don't think that a timing receiver adds much value except possibly the ability to still work with one or two sats visible.   Many GPS/GLONAS/BEIDOU capable timing receivers don't do precision timing with more than one sat system type enabled...  I think the Venus devices are like that... they only to GPS timing.
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