[time-nuts] question Alan deviation measured with Timelab and counters

[steph.rey]

 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 
 <bruce.griffiths at xtra.co.nz> 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
> <steph.rey at wanadoo.fr> 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:time-nuts-bounces at febo.com] 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 <steph.rey at wanadoo.fr> 
>> 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:time-nuts-bounces at febo.com] 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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