Paper about DCF77 performance
Hi,
This is my first post to this mailing list. I wrote a paper about the
German longwave time transmitter DCF77 which you may find interesting.
Here is the link, unfortunately I am not allowed to post the full PDF:
http://ieeexplore.ieee.org/xpl/articleDetails.jsp?tp=&arnumber=6202411
"Performance Analysis and Receiver Architectures of DCF77
Radio-Controlled Clocks", by Daniel Engeler
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control
(May 2012)
Abstract:
DCF77 is a longwave radio transmitter located in Germany. Atomic
clocks generate a 77.5-kHz carrier which is amplitude- and
phase-modulated to broadcast the official time. The signal is used by
industrial and consumer radio-controlled clocks. DCF77 faces
competition from the Global Positioning System (GPS) which provides
higher accuracy time. Still, DCF77 and other longwave time services
worldwide remain popular because they allow indoor reception at lower
cost, lower power, and sufficient accuracy. Indoor longwave reception
is challenged by signal attenuation and electromagnetic interference
from an increasing number of devices, particularly switched-mode power
supplies. This paper introduces new receiver architectures and
compares them with existing detectors and time decoders. Simulations
and analytical calculations characterize the performance in terms of
bit error rate and decoding probability, depending on input noise and
narrowband interference. The most promising detector with
maximum-likelihood time decoder displays the time in less than 60 s
after powerup and at a noise level of Eb/N0 = 2.7 dB, an improvement
of 20 dB over previous receivers. A field-programmable gate
array-based demonstration receiver built for the purposes of this
paper confirms the capabilities of these new algorithms. The findings
of this paper enable future high-performance DCF77 receivers and
further study of indoor longwave reception.
On 6/13/2012 3:46 PM, Daniel Engeler wrote:
Hi,
This is my first post to this mailing list. I wrote a paper about the
German longwave time transmitter DCF77 which you may find interesting.
Here is the link, unfortunately I am not allowed to post the full PDF:
http://ieeexplore.ieee.org/xpl/articleDetails.jsp?tp=&arnumber=6202411
"Performance Analysis and Receiver Architectures of DCF77
Radio-Controlled Clocks", by Daniel Engeler
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control
(May 2012)
Abstract:
DCF77 is a longwave radio transmitter located in Germany. Atomic
clocks generate a 77.5-kHz carrier which is amplitude- and
phase-modulated to broadcast the official time. The signal is used by
industrial and consumer radio-controlled clocks. DCF77 faces
competition from the Global Positioning System (GPS) which provides
higher accuracy time. Still, DCF77 and other longwave time services
worldwide remain popular because they allow indoor reception at lower
cost, lower power, and sufficient accuracy. Indoor longwave reception
is challenged by signal attenuation and electromagnetic interference
from an increasing number of devices, particularly switched-mode power
supplies. This paper introduces new receiver architectures and
compares them with existing detectors and time decoders. Simulations
and analytical calculations characterize the performance in terms of
bit error rate and decoding probability, depending on input noise and
narrowband interference. The most promising detector with
maximum-likelihood time decoder displays the time in less than 60 s
after powerup and at a noise level of Eb/N0 = 2.7 dB, an improvement
of 20 dB over previous receivers. A field-programmable gate
array-based demonstration receiver built for the purposes of this
paper confirms the capabilities of these new algorithms. The findings
of this paper enable future high-performance DCF77 receivers and
further study of indoor longwave reception.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Daniel
Might be a great read for us time-nuts. Unfortunately we have no access
to the ieee site so it will go unread and appreciated.
Regards
Paul
Would be interesting if I can read it.
As far as I know even the IEEE grants the right to the author of his
paper to locate it on his own web-site for public download.
Thanks -
Henry
paul schrieb:
On 6/13/2012 3:46 PM, Daniel Engeler wrote:
Hi,
This is my first post to this mailing list. I wrote a paper about the
German longwave time transmitter DCF77 which you may find interesting.
Here is the link, unfortunately I am not allowed to post the full PDF:
http://ieeexplore.ieee.org/xpl/articleDetails.jsp?tp=&arnumber=6202411
Daniel
Might be a great read for us time-nuts. Unfortunately we have no access
to the ieee site so it will go unread and appreciated.
Regards
Paul
--
ehydra.dyndns.info
Hi
Do they grant the right, or do people just get away with it?
Bob
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of ehydra
Sent: Wednesday, June 13, 2012 4:24 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Paper about DCF77 performance
Would be interesting if I can read it.
As far as I know even the IEEE grants the right to the author of his
paper to locate it on his own web-site for public download.
Thanks -
Henry
paul schrieb:
On 6/13/2012 3:46 PM, Daniel Engeler wrote:
Hi,
This is my first post to this mailing list. I wrote a paper about the
German longwave time transmitter DCF77 which you may find interesting.
Here is the link, unfortunately I am not allowed to post the full PDF:
http://ieeexplore.ieee.org/xpl/articleDetails.jsp?tp=&arnumber=6202411
Daniel
Might be a great read for us time-nuts. Unfortunately we have no access
to the ieee site so it will go unread and appreciated.
Regards
Paul
--
ehydra.dyndns.info
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
On 6/13/12 1:38 PM, Bob Camp wrote:
Hi
Do they grant the right, or do people just get away with it?
it is formally granted.. the IEEE instructions for authors or something
like that talks about it.
You can put your own papers up on your own website, and you make sure
you have appropriate attribution, etc.
I'll look for the reference.
Hoi Dani!
I see you've found the time-nuts as well :-)
On Wed, 13 Jun 2012 21:46:56 +0200
Daniel Engeler engeler@alumni.ethz.ch wrote:
This is my first post to this mailing list. I wrote a paper about the
German longwave time transmitter DCF77 which you may find interesting.
Here is the link, unfortunately I am not allowed to post the full PDF:
There is an easy way to get around that: Prepare a second paper with
more data in it (all that stuff that IEEE tends to get rid of during
the publication process) and put that onto your website.
http://ieeexplore.ieee.org/xpl/articleDetails.jsp?tp=&arnumber=6202411
"Performance Analysis and Receiver Architectures of DCF77
Radio-Controlled Clocks", by Daniel Engeler
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control
(May 2012)
Nice paper. I haven't had time to read it yet, but a few comments
after i skimmed it:
-
you have a lot of simulation and measurments on BER vs SNR. For time-nutty
needs that's not so relevant. An ADEV plot would be much more informative
on the stability. -
Also some data on the absolute timing variations vs time would be
nice to have. -
Fig 23 shows a very complex board. Given that you only have a relatively
simple analog stage and an FPGA i wonder what the rest is for. -
You use an LTC1562 8th order bandpass: Do you compensate for it's frequency
dependend delay and its variation? Or is negligible compared to the antenna? -
Do you do any temperature stabilization?
-
What kind of reference oscillator do you use?
-
You talk about 20 to 50ppm variations for XO's, are you aware that these
are maximum variation including production variabiltiy and that the stability
of an good XO is usually in the range of a few ppm in office conditions
(i've measured an XO in a PC that showed a long term (months) stability
in the ppb range) -
Why did you use an FPGA and not a simple DSP or one of the more powerfull
uC's like an Cortex-M3/4? The algorigthms don't look computationally intensive.
And that would simplify the development considerably. -
Where did you do your measurements? In Schlieren?
-
What is the application you had in mind while developing this?
Attila Kinali
--
Why does it take years to find the answers to
the questions one should have asked long ago?
Hi Attila
Thanks for the feedback.
- you have a lot of simulation and measurments on BER vs SNR. For time-nutty
needs that's not so relevant. An ADEV plot would be much more informative
on the stability. - Also some data on the absolute timing variations vs time would be
nice to have.
Yes that would be nice, but my spare time is short for this and the
dozens of other ideas I have.
- Fig 23 shows a very complex board. Given that you only have a relatively
simple analog stage and an FPGA i wonder what the rest is for.
Just the usual power supply, DAC for debugging FPGA-internal signals,
galvanically isolated USB for logging, debug headers.
- You use an LTC1562 8th order bandpass: Do you compensate for it's frequency
dependend delay and its variation? Or is negligible compared to the antenna?
I do compensate for it. The remaining uncertainty is taken into
account in the paper.
- Do you do any temperature stabilization?
No, but it would be a nice addition.
- What kind of reference oscillator do you use?
Abracon ASV-12.000MHZ-E-J-T, 20 ppm, 12 MHz
- You talk about 20 to 50ppm variations for XO's, are you aware that these
are maximum variation including production variabiltiy and that the stability
of an good XO is usually in the range of a few ppm in office conditions
(i've measured an XO in a PC that showed a long term (months) stability
in the ppb range)
I worked with worst-case ranges as if it were a mass production.
- Why did you use an FPGA and not a simple DSP or one of the more powerfull
uC's like an Cortex-M3/4? The algorigthms don't look computationally intensive.
And that would simplify the development considerably.
At that time, I wanted to have some fun with FPGAs. It would also work
on a uC, which BTW already is my next project. Both ways have
advantages, for example the clock correction algorithm is easier to
implement on an FPGA, while the signal processing would be simpler on
a uC.
- Where did you do your measurements? In Schlieren?
Yes.
- What is the application you had in mind while developing this?
Building the best DCF77 receiver in the world :-)
Regards,
Daniel
Attila,
An ADEV plot would be much more informative on the stability.
I have found an old publication from former PTB researcher Dr. Peter Hetzel.
This publication holds a diagram which (while not being exactly an ADEV
plot) holds some interesting information on the topic: It shows the STANDARD
DEVIATION of timing measurements made on DCF77's signal abt. 273 km away
from the transmitter location as a function of the averaging time of the
measurements. So no ADEV but coming close...
The diagram starts at abt. 8E-8 std dev for 1 s avaraging time and is
basically a straight line with a slope of abt. -0.8. that extends to 7E-14
for averaging times of 100 days. I list a few values:
8E-8 @ 1 s
1E-9 @ 10 s
2E-10 @ 100 s
5E-11 @ 1000 s
2E-12 @ 1 d
3E-13 @ 10 d
7E-14 @ 100 d
The diagram has no log sub scale so the readings are my estimate. The
diagram hold a lot of individual points between 10 and 100 days averaging
time indicating that a lot of measurements with that averaging times have
really been done.
Best regards
Ulrich Bangert
-----Ursprungliche Nachricht-----
Von: time-nuts-bounces@febo.com
[mailto:time-nuts-bounces@febo.com] Im Auftrag von Attila Kinali
Gesendet: Donnerstag, 14. Juni 2012 07:56
An: Discussion of precise time and frequency measurement
Betreff: Re: [time-nuts] Paper about DCF77 performance
Hoi Dani!
I see you've found the time-nuts as well :-)
On Wed, 13 Jun 2012 21:46:56 +0200
Daniel Engeler engeler@alumni.ethz.ch wrote:
This is my first post to this mailing list. I wrote a paper
about the
German longwave time transmitter DCF77 which you may find
interesting.
Here is the link, unfortunately I am not allowed to post
the full PDF:
There is an easy way to get around that: Prepare a second
paper with more data in it (all that stuff that IEEE tends to
get rid of during the publication process) and put that onto
your website.
"Performance Analysis and Receiver Architectures of DCF77
Radio-Controlled Clocks", by Daniel Engeler IEEE Transactions on
Ultrasonics, Ferroelectrics and Frequency Control (May 2012)
Nice paper. I haven't had time to read it yet, but a few
comments after i skimmed it:
-
you have a lot of simulation and measurments on BER vs SNR.
For time-nutty needs that's not so relevant. An ADEV plot
would be much more informative on the stability. -
Also some data on the absolute timing variations vs time
would be nice to have. -
Fig 23 shows a very complex board. Given that you only have
a relatively simple analog stage and an FPGA i wonder what
the rest is for. -
You use an LTC1562 8th order bandpass: Do you compensate
for it's frequency dependend delay and its variation? Or is
negligible compared to the antenna? -
Do you do any temperature stabilization?
-
What kind of reference oscillator do you use?
-
You talk about 20 to 50ppm variations for XO's, are you
aware that these are maximum variation including production
variabiltiy and that the stability of an good XO is usually
in the range of a few ppm in office conditions (i've measured
an XO in a PC that showed a long term (months) stability in
the ppb range) -
Why did you use an FPGA and not a simple DSP or one of the
more powerfull uC's like an Cortex-M3/4? The algorigthms
don't look computationally intensive. And that would simplify
the development considerably. -
Where did you do your measurements? In Schlieren?
-
What is the application you had in mind while developing this?
Attila Kinali
--
Why does it take years to find the answers to
the questions one should have asked long ago?
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.