Thanks a lot for your comment Bruce,
I need to feel a bit deeper the ins and outs of the methods so I guess
I will anyway implement both methods on an evaluation PCB and
characterize each method. This will bring to me some actual data to
compare. I will share the results of course.
The plan is to have an eval PCB with 4 independant 10 MHz squarers,
isolation amplifiers, mixers, low pass filters and multistage limiting
amplifier. Each block will have input/output connectors so that I can
combine any architecture with these blocks. The PCB will receive a low
noise PSU as well.
Before I start the design if one thinks about something to add in the
evaluation, this is very welcome.
Stephane
On Tue, 27 Jan 2015 03:24:44 +0000 (UTC), Bruce Griffiths
<[email protected]> wrote:
The performance of the 2 systems should be comparable provided the
similar equivalent noise bandwidths are used.Every 10Mhz edge needs
to
be timestamped with ps resolution and the resulting phase samples low
pass filtered and decimated to achieve this.The 10MSPS picosecond or
better resolution time stamping with femtosecond integral linearity
will be a bit of a challenge to achieve.
Bruce
On Tuesday, 27 January 2015 3:26 PM, Stéphane Rey
<[email protected]> wrote:
I do understand.
Has anyone already compared the performances of squaring the 10 MHz
vs squaring the IF ?
Stephane
-----Message d'origine-----
De : time-nuts [mailto:[email protected]] De la part de Bob
Camp
Envoyé : dimanche 25 janvier 2015 19:01
À : Discussion of precise time and frequency measurement
Objet : Re: [time-nuts] question Alan deviation measured with Timelab
and counters
Hi
The approach in the original NIST paper below was sort of a “best
guess” about how to do the limiting and filtering. When the paper was
presented, a number of us questioned how that part of the circuit was
arrived at. The conversation more or less ended up with “that’s
something we can investigate further”. The Collins paper (and Bruce’s
work based on it) is a much better way to look at the 10 Hz squaring
process. At 10 MHz, that stuff is not needed.
Bob
On Jan 25, 2015, at 10:44 AM, Stéphane Rey <[email protected]>
wrote:
Hi everyone.
Many thanks for your very useful comments.
I had already seen most of the documents you were pointing but not
on
the collins and Bruce discussion around the multistage filter.
However
I've already seen this approach in the document from Allan
(http://tf.nist.gov/timefreq/general/pdf/84.pdf)
At first I had in mind to square the 10 MHz but this is the aim of
the
evaluation board to evaluate various architectures. So I will
implement several squarers including the Collins Approach both at 10
MHz and 100 Hz and all the blocks will have input and output
connectors so that I will be able to test several layouts.
I will show you the final design.
Cheers
Stephane
-----Message d'origine-----
De : time-nuts [mailto:[email protected]] De la part de
Charles Steinmetz Envoyé : dimanche 25 janvier 2015 08:08 À :
Discussion of precise time and frequency measurement Objet : Re:
[time-nuts] question Alan deviation measured with Timelab and
counters
Stephane wrote:
I'm now trying to evaluate various architectures of 2-channels
squarers and a DMDT. For that I'm designing a PCB with 4 squarers :
simple 74ac04 gate biased at VCC/2, a LT1016 comparator, the
transistor based differential amplifier from Winzel and the one
from Charles.
Note that squaring a 10MHz sine wave and squaring a 10 or 100Hz
mixer
output are two very different tasks. If you start at baseband, a
Collins-style multi-stage limiting amp is a great benefit. That is
generally not necessary if you start at 10MHz (or if you do use a
Collins-style limiter it needs far fewer stages). All of the
squarers
you mention work well at 10MHz, but not as well at baseband.
The LT1719 is easier to apply and faster than the LT1016. You may
want to use that instead of the 1016. The LT1719 and LT1715
datasheets show the simplest possible implementation (see below).
The MPSH81 devices in my version are available in surface-mount
(MMBTH81) if that is more convenient. Other fast transistors will
also work (BFT92, BFT93, BFG31).
Best regards,
Charles
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