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

[Stéphane Rey]

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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