Beginning of the 20th century it was realized that radio waves were the
best medium to distribute time information.
Between 1910 to1916 vessel communication station called Norddeich Radio,
located in Germany, provided the first, but not for public use time code
transmission.
From 1917 on the German public broadcast station called NAUEN distributed
2 times a day time code information for public use on long wave
During the years a global network of Time Code Station was built.
Additional to the terrestrial based station also a network of satellites
was brought to the orbit for international exchange of time information.
Beside the satellite based time transmitters, long wave is still a very
important means of distribution of the signal.
The behavior of long wave frequency allows simply distribution to large
areas.
The waves are able to penetrate buildings and can also be received in
certain distance under ground. The receiver and its antenna can be build
small and economically.
The satellite based network is not suitable for consumer products, because
of the behavior of the high frequency this signal is not able to be received
inside buildings or anywhere is being obstructed from sky. The signal
is damped from each part between antenna and satellite. Even rain and
fog are able to damp the signal.
Since 1986, application of the time code receiver has been a
big success for all types of consumer products.
1986
The first time code receiver was developed
from TEMIC in cooperation with Junghans.
All the earlies, more or less discrete
solutions, were super-heterodyne receiver with bulky crystal filters
and a lot of transistors mainly located in a transistor-array. These
solutions where always main powered and current consumption was no
criteria.
The new developed concept used a straightforward principle. This offered
the possibility of lower power consumption (250µA) as well as
a supply range down to 1 Volt.
1988
A new solution under the technical
leadership of Junghans
Together with the FFMU, the Research institute
of the Research Community for Micro mechanic and Watch Techniques
at Stuttgart was developed.
The topic of this device was a amplitude-frequency-converter.
Also the sensitivity was increased. This chip was controlled by a
micro controller. But this solution was not very successful, because
the software for the micro controller was more extensive than
only for decoding and time keeping.
1988
The company Ruhla in the former GDR
starts to develop time code controlled applications
An indepentent software and hardware solution
for RC watches was developed by the "Ruhla" company. A super-HET
solution was used as receiver.
1990
A new IC under contract which Junghans
was developed from Temic
The packed version of this IC was free
for the open market. With this design the power consumption was
drastically reduced (by factor 10) to 25 µA. It was still
the concept of straightforward receiver what was used. A reduction
of external components was going along with this new design.
1990
HKW starts after reunion of Germany
a development of an own time code receiver
Based on the know-how as a former developer
for the Ruhla company, HKW specialized on the development of RF watch
and clock technique.
1991
First receiver from HKW in Super heterodyne
technique
This receiver was a solution with two antenna
inputs, which could be switched by a micro-controller in order to
achieve a omni-directional reception.
1992
A special low cost version, not free
for the open market was developed together with Junghans and Temic.
The IC had an internal selection and does
not need any addition crystal. As a PLL principle, the 32kHz crystal
at the micro was used. This design was not too successful, because
in difficult receiving areas the receiver with an own crystal filter
was the better choice.
1992
HKW introduced the first straightforward
receiver with two input possibilities for different antenna selections
This improved gerneration of the HKW receiver
needs less components.
1994
HKW introduced the second-generation
receiver to the market
This receiver was an extended version for
the use 1,5 V and 3 V Applications
1995
A new development, independent from
Junghans, was started from TEMIC.
The intention of this, still existing,
design was to be free for the open market without restrictions and
furthermore to combine all the experience together to have a reliable
and sensitive as well as current saving solution.
The current consumption of this chip is about 15 µA and the
sensitivity was again slightly increased by better stability. A new
principle of decoding was introduced by using an A/D converter in
order to gain more information out of the received signal.
1996
HKW offered the 3rd generation of
time code receivers
This 3rd generation was again optimized
in sensitivity and current consumption
1998
C-MAX decided to take over the distribution
for time code receivers from HKW
C-MAX, a leading manufacturer and distributor
of various RF-devices, takes over sales and marketing activities for
HKW receivers with big success in Asia .
1999
Temic (now named Atmel) and HKW decided
together to do a new design
It was the intention of both companies,
Atmel and HKW, to combine their know how to provide to the market
the most professional and state of the art solution. The new part
replaces all the designs with similar function with exception of the
automotive part existing at Atmel's portfolio. The new design was
improved in sensitivity and needs less external components. Designing
with this part is more easy than ever before.
2000
Release of the new IC development
UE6005 to the market
2001
Start of the IC production
2002
C-MAX start the development of a revolutionary new
IC design
With the intention to create an optimised receiver
IC with
extended features and to meet customer needs more explicit, C-MAX
starts the development of a new generation of receiver IC's
2003
Introduction of the new receiver IC CME8000
to the market
2004
Start of the IC production
What is time
Based on international conventions, the second is defined as 9 192 631
770 times of the time, a Caesium Nuclide (133Cs) needs to change from
one to the other energetic level. This time is much more precise known
than for instance the time period of a mechanical resonator. The change
of the energetic levels can be forced and the Caesium-atom emits a frequency
of 9 192 631 770 Hz.
Time from a fountain of cold atoms
Since 1967, the second has been defined via the resonance frequency between
selected energy levels of the atom caesium 133, a non-radioactive element.
The definition followed development and common understanding of atomic
physics and quantum mechanics and demonstration of the first caesium atomic
clock with a thermal atomic beam in 1955. This unassuming device is a
caesium frequency standard, sometimes referred to as an atomic clock.
In many respects the atomic fountain clock is just the logical further
development of the atomic clocks with a thermal atomic beam, which have
been in operation long time. As early as in the fifties, Jerrold Zacharias
of the Massachusetts Institute of Technology tried to prolong the time
of flight in relation to that achievable with a thermal atomic beam. To
reach this aim, he tried to set up the first caesium fountain in which
the slow atoms from a vertical thermal source were to turn back under
the effect of the gravitational force. He wanted to prove that their state
had changed after they had flown through the same resonator field while
rising and falling down again. Zacharias was not successful: By collisions
in the area of the atomic beam source the number of sufficiently slow
atoms in his thermal beam, which was small anyhow, was reduced to such
an extent that no signal could be detected. The atoms were too "hot";
their relative velocities too high.
The situation is altogether different today: By
laser cooling cold caesium atoms are collected in a cloud . The
relative velocities of these atoms lying in the range of one to
a few cm/s. NIST-F1, the time and frequency standard for US, is
a caesium fountain atomic clock developed at the NIST laboratories
in Boulder, Colorado.
First, a gas of caesium atoms is introduced into the clock's vacuum
chamber. Six infrared laser beams then are directed at right angles
to each other at the centre of the chamber. The lasers gently push
the caesium atoms together into a ball. In the process of creating
this ball, the lasers slow down the movement of the atoms. Laser
cooling drops the temperature of the atoms to a few millionths of
a degree above absolute zero, and reduces their thermal velocity
to a few centimetres per second
Two vertical lasers are used to gently toss the ball upward (the
"fountain" action), and then all of the lasers are turned
off. This little push is just enough to loft the ball about a meter
high through a microwave-filled cavity. Under the influence of gravity,
the ball then falls back down through the microwave cavity. A scenario
which reminds one of a fountain.
In a similar way as in a conventional atomic clock the energy state
of the atoms is manipulated and checked. At the beginning the atoms
are prepared in a single energy state; during the up- and down-movement
they fly, however, through the same microwave field. The laser cooled
atoms pass twice through a microwave cavity, once on the way up
and once on the way down. The result is an observation time of about
one second, which is limited only by the force of gravity pulling
the atoms to the ground.
During the trip, the atomic states of the atoms might or might not be
altered as they interact with the microwave signal. When their trip is
finished, another laser is pointed at the atoms. Those atoms whose atomic
state were altered by the microwave signal emit light (a state known as
fluorescence). The photons, or the tiny packets of light that they emit,
are measured by a detector.
This process is repeated many times while the microwave signal in the
cavity is tuned to different frequencies. Eventually, a microwave frequency
is found that alters the states of most of the caesium atoms and maximise
their fluorescence. This frequency is the natural resonance frequency
of the caesium atom (9 192 631 770 Hz), or the frequency used to define
the second.
As you might guess, the longer observation times make it easier to tune
the microwave frequency. The improved tuning of the microwave frequency
leads to a better realisation and control of the resonance frequency of
caesium. And of course, the improved frequency control leads to what is
one of the world's most accurate clocks.
The signal from the atomic clock is fed to a unit called a Time Code Generator.
This produces the time code which is distributed by each station.
The signal must now be amplified by powerful radio transmitters and distributed
via radiowaves. Radiowaves travel at the speed of light (~300 000 km per
second).
This is the way we can participate at this accurate clock (description
according information's from NIST and PTT)
Background of Time code reception
Time code transmitters are different from such for Audio or TV broadcasting.
They provide information of the present time (based on an atomic time
normal - see above) the day, the month
and the year and the relevant Daylight saving time. The information is
transmitted via a long wave transmitter in the frequency range of 40 to
80 kHz. This frequency range is the best solution to construct receivers
with low power consumption. The transmitters are amplitude modulated.
The information is a bit stream with pulses in different length. Every
second a pulse is transmitted. All the information is transferred in one
minute time frame
All time laboratories around the world are using this frequency as the
time-base.
