Re: [time-nuts] Frequency standards for different tau in Allen Dev measurement

[Robert DiRosario via time-nuts]

SDRs (Software Defined Radio) decimate / downsample.  Look at SDR 
documentation.


Google turns up: https://dspguru.com/dsp/faqs/multirate/decimation/

Robert

On 02/21/2020 03:09 PM, Gary E. Miller via time-nuts wrote:

Yo Magnus!

On Fri, 21 Feb 2020 20:33:46 +0100
Magnus Danielson via time-nuts  wrote:


As one decimate data, one needs to be very very careful with
bandwidth. It would make biases in values which would over-state
stability. Yes, we have seen it happen. Even big names has come clean
and confessed doing it wrong when they decimated the data.

Anyone have any references to how to decimate properly?

RGDS
GARY
---
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
g...@rellim.com  Tel:+1 541 382 8588

Veritas liberabit vos. -- Quid est veritas?
 "If you can't measure it, you can't improve it." - Lord Kelvin


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Re: [time-nuts] A simple sampling DMTD

[Bob kb8tq via time-nuts]

Hi

Ok, but thats “high pass in the RF section”. You really do not have an audio 
high pass 
filter the way you would in a more typical DMTD. 

If it’s any comfort, I’m sitting here looking at a very different box. It also 
has “wobbles”
as you get into parts in 10^-16. That might change a bit if the draft coming 
through the
window was a bit less.

Bob

> On Feb 23, 2020, at 6:12 PM, Jan-Derk Bakker  wrote:
> 
> Dear Bob,
> 
> The capacitors are 47n NP0/C0G types (Kemet C0805C473K3GAC7800), picked for 
> low tempco (and low DF and other non-ideal behavior). I've not spotted any 
> hysteresis artefacts in these in previous designs, but I haven't measured 
> their performance in this circuit.
> 
> Forgot to mention in the previous message: the baluns are transformers 
> (M/A-COM MABAES0060), so the only DC the ADC should see is its own input 
> offset (plus offset current across the 25R input filter resistors). Full 
> schematic is here ( http://www.lartmaker.nl/time-nuts/DMTD_rev0.99.pdf 
>  ; needs cleanup, but all 
> connections are there).
> 
> JDB.
> 
> On Sun, Feb 23, 2020 at 10:13 PM Bob kb8tq  > wrote:
> Hi
> 
> What does the temperature coefficient of your “hardware HPF” filter caps look 
> like?
> Are they a type that has significant hysteresis?
> 
> Bob
> 
> > On Feb 23, 2020, at 3:05 PM, Jan-Derk Bakker via time-nuts 
> > mailto:time-nuts@lists.febo.com>> wrote:
> > 
> > Dear Attila,
> > 
> > Thanks for the heads up.
> > 
> > I am currently using a HPF both in hardware (capacitive coupling into the
> > balun driving the ADC inputs) and in software before the ZCD. This should
> > counteract the first-order effects of this offset, although second-order
> > effects (converter nonlinearity et al) will of course still be an issue.
> > The plots you've quoted include (different kinds of) DC offset correction
> > for all but the "unfiltered" data; getting an efficient DC offset
> > correction working in real time on this 8-bit platform was indeed one of
> > the main challenges of the software-only approach.
> > 
> > The FPGA daughterboard is currently in production at Eurocircuits; I hope
> > to have time to work on those the coming month. I'll also try to book some
> > time in our climate chamber. (I've had one of our GPSDO-designs running in
> > our general labs since before Christmas; surrounding it with bottles of
> > water works well enough to low pass filter temperature swings, but I still
> > see 6 degrees C swings overnight as out HVAC only runs during business
> > hours.)
> > 
> > To be continued,
> > 
> > JDB.
> > 
> > On Sun, Feb 23, 2020 at 8:11 PM Attila Kinali via time-nuts <
> > time-nuts@lists.febo.com > wrote:
> > 
> >> Good evening!
> >> 
> >> I'm going through some old stuff...
> >> 
> >> 
> >> On Wed, 27 Nov 2019 00:29:19 +0100
> >> Jan-Derk Bakker mailto:jdbak...@gmail.com>> wrote:
> >> 
> >>> This has yielded a combined "simple" signal
> >>> processing path of a differentiator, a double comb filter and the offset
> >>> estimator, which is getting very close in performance to the "ideal" band
> >>> pass filter (OADEV of 3.77e-13@tau=1s versus 3.25e-13@tau=1s for the
> >> BPF;
> >>> full plot:
> >>> 
> >> http://www.lartmaker.nl/time-nuts/DMTD%20self-noise%20OADEV%20with%20PLL%20and%20various%20filters.pdf
> >>  
> >> 
> >>> for this 60-second recording:
> >>> 
> >> http://www.lartmaker.nl/time-nuts/600ksec%20run%20with%20PLL,%2010811%20through%20splitter.png
> >>  
> >> 
> >>> . OADEV past ~1000sec is severely compromised by the fact that the
> >>> measurement setup is in my home lab which sees temperature swings of up
> >> to
> >>> 20 degrees C and which does get bumped from time to time. Longer runs in
> >> a
> >>> more controlled setting forthcoming).
> >> 
> >> 
> >> I can offer an explanation for the large effect of the zero correction seen
> >> here. The LTC2140 is specified to have a +/-10µV/°C drift (at 1Vpp
> >> setting).
> >> Converted into phase error due to zero crossing shift, this turns into
> >> a phase shift of +/-1ps/°C @ 10MHz. Note, the shift is given as +/- and
> >> per channel, which means, it could very well be that the channels are
> >> not matched in their temperature characteristics and thus the total phase
> >> shift could be +/-2ps/°C ... though total shift being closer to 0.5ps/°C is
> >> more likely.
> >> 
> >> Summa sumarum: DC offset correction is important if a zero crossing
> >> detector is used.
> >> 
> >>Attila Kinali
> >> 
> >> --
> >> The bad part of Zurich is where the degenerates
> >>throw DARK chocolate at you.
> >> 
> >> ___
> >> time-nuts ma

Re: [time-nuts] A simple sampling DMTD

[Jan-Derk Bakker via time-nuts]

Dear Bob,

The capacitors are 47n NP0/C0G types (Kemet C0805C473K3GAC7800), picked for
low tempco (and low DF and other non-ideal behavior). I've not spotted any
hysteresis artefacts in these in previous designs, but I haven't measured
their performance in this circuit.

Forgot to mention in the previous message: the baluns are transformers
(M/A-COM MABAES0060), so the only DC the ADC should see is its own input
offset (plus offset current across the 25R input filter resistors). Full
schematic is here ( http://www.lartmaker.nl/time-nuts/DMTD_rev0.99.pdf ;
needs cleanup, but all connections are there).

JDB.

On Sun, Feb 23, 2020 at 10:13 PM Bob kb8tq  wrote:

> Hi
>
> What does the temperature coefficient of your “hardware HPF” filter caps
> look like?
> Are they a type that has significant hysteresis?
>
> Bob
>
> > On Feb 23, 2020, at 3:05 PM, Jan-Derk Bakker via time-nuts <
> time-nuts@lists.febo.com> wrote:
> >
> > Dear Attila,
> >
> > Thanks for the heads up.
> >
> > I am currently using a HPF both in hardware (capacitive coupling into the
> > balun driving the ADC inputs) and in software before the ZCD. This should
> > counteract the first-order effects of this offset, although second-order
> > effects (converter nonlinearity et al) will of course still be an issue.
> > The plots you've quoted include (different kinds of) DC offset correction
> > for all but the "unfiltered" data; getting an efficient DC offset
> > correction working in real time on this 8-bit platform was indeed one of
> > the main challenges of the software-only approach.
> >
> > The FPGA daughterboard is currently in production at Eurocircuits; I hope
> > to have time to work on those the coming month. I'll also try to book
> some
> > time in our climate chamber. (I've had one of our GPSDO-designs running
> in
> > our general labs since before Christmas; surrounding it with bottles of
> > water works well enough to low pass filter temperature swings, but I
> still
> > see 6 degrees C swings overnight as out HVAC only runs during business
> > hours.)
> >
> > To be continued,
> >
> > JDB.
> >
> > On Sun, Feb 23, 2020 at 8:11 PM Attila Kinali via time-nuts <
> > time-nuts@lists.febo.com> wrote:
> >
> >> Good evening!
> >>
> >> I'm going through some old stuff...
> >>
> >>
> >> On Wed, 27 Nov 2019 00:29:19 +0100
> >> Jan-Derk Bakker  wrote:
> >>
> >>> This has yielded a combined "simple" signal
> >>> processing path of a differentiator, a double comb filter and the
> offset
> >>> estimator, which is getting very close in performance to the "ideal"
> band
> >>> pass filter (OADEV of 3.77e-13@tau=1s versus 3.25e-13@tau=1s for the
> >> BPF;
> >>> full plot:
> >>>
> >>
> http://www.lartmaker.nl/time-nuts/DMTD%20self-noise%20OADEV%20with%20PLL%20and%20various%20filters.pdf
> >>> for this 60-second recording:
> >>>
> >>
> http://www.lartmaker.nl/time-nuts/600ksec%20run%20with%20PLL,%2010811%20through%20splitter.png
> >>> . OADEV past ~1000sec is severely compromised by the fact that the
> >>> measurement setup is in my home lab which sees temperature swings of up
> >> to
> >>> 20 degrees C and which does get bumped from time to time. Longer runs
> in
> >> a
> >>> more controlled setting forthcoming).
> >>
> >>
> >> I can offer an explanation for the large effect of the zero correction
> seen
> >> here. The LTC2140 is specified to have a +/-10µV/°C drift (at 1Vpp
> >> setting).
> >> Converted into phase error due to zero crossing shift, this turns into
> >> a phase shift of +/-1ps/°C @ 10MHz. Note, the shift is given as +/- and
> >> per channel, which means, it could very well be that the channels are
> >> not matched in their temperature characteristics and thus the total
> phase
> >> shift could be +/-2ps/°C ... though total shift being closer to
> 0.5ps/°C is
> >> more likely.
> >>
> >> Summa sumarum: DC offset correction is important if a zero crossing
> >> detector is used.
> >>
> >>Attila Kinali
> >>
> >> --
> >> The bad part of Zurich is where the degenerates
> >>throw DARK chocolate at you.
> >>
> >> ___
> >> time-nuts mailing list -- time-nuts@lists.febo.com
> >> To unsubscribe, go to
> >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> >> and follow the instructions there.
> >>
> > ___
> > time-nuts mailing list -- time-nuts@lists.febo.com
> > To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > and follow the instructions there.
>
>
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Re: [time-nuts] A simple sampling DMTD

[Bob kb8tq via time-nuts]

Hi

What does the temperature coefficient of your “hardware HPF” filter caps look 
like?
Are they a type that has significant hysteresis?

Bob

> On Feb 23, 2020, at 3:05 PM, Jan-Derk Bakker via time-nuts 
>  wrote:
> 
> Dear Attila,
> 
> Thanks for the heads up.
> 
> I am currently using a HPF both in hardware (capacitive coupling into the
> balun driving the ADC inputs) and in software before the ZCD. This should
> counteract the first-order effects of this offset, although second-order
> effects (converter nonlinearity et al) will of course still be an issue.
> The plots you've quoted include (different kinds of) DC offset correction
> for all but the "unfiltered" data; getting an efficient DC offset
> correction working in real time on this 8-bit platform was indeed one of
> the main challenges of the software-only approach.
> 
> The FPGA daughterboard is currently in production at Eurocircuits; I hope
> to have time to work on those the coming month. I'll also try to book some
> time in our climate chamber. (I've had one of our GPSDO-designs running in
> our general labs since before Christmas; surrounding it with bottles of
> water works well enough to low pass filter temperature swings, but I still
> see 6 degrees C swings overnight as out HVAC only runs during business
> hours.)
> 
> To be continued,
> 
> JDB.
> 
> On Sun, Feb 23, 2020 at 8:11 PM Attila Kinali via time-nuts <
> time-nuts@lists.febo.com> wrote:
> 
>> Good evening!
>> 
>> I'm going through some old stuff...
>> 
>> 
>> On Wed, 27 Nov 2019 00:29:19 +0100
>> Jan-Derk Bakker  wrote:
>> 
>>> This has yielded a combined "simple" signal
>>> processing path of a differentiator, a double comb filter and the offset
>>> estimator, which is getting very close in performance to the "ideal" band
>>> pass filter (OADEV of 3.77e-13@tau=1s versus 3.25e-13@tau=1s for the
>> BPF;
>>> full plot:
>>> 
>> http://www.lartmaker.nl/time-nuts/DMTD%20self-noise%20OADEV%20with%20PLL%20and%20various%20filters.pdf
>>> for this 60-second recording:
>>> 
>> http://www.lartmaker.nl/time-nuts/600ksec%20run%20with%20PLL,%2010811%20through%20splitter.png
>>> . OADEV past ~1000sec is severely compromised by the fact that the
>>> measurement setup is in my home lab which sees temperature swings of up
>> to
>>> 20 degrees C and which does get bumped from time to time. Longer runs in
>> a
>>> more controlled setting forthcoming).
>> 
>> 
>> I can offer an explanation for the large effect of the zero correction seen
>> here. The LTC2140 is specified to have a +/-10µV/°C drift (at 1Vpp
>> setting).
>> Converted into phase error due to zero crossing shift, this turns into
>> a phase shift of +/-1ps/°C @ 10MHz. Note, the shift is given as +/- and
>> per channel, which means, it could very well be that the channels are
>> not matched in their temperature characteristics and thus the total phase
>> shift could be +/-2ps/°C ... though total shift being closer to 0.5ps/°C is
>> more likely.
>> 
>> Summa sumarum: DC offset correction is important if a zero crossing
>> detector is used.
>> 
>>Attila Kinali
>> 
>> --
>> The bad part of Zurich is where the degenerates
>>throw DARK chocolate at you.
>> 
>> ___
>> time-nuts mailing list -- time-nuts@lists.febo.com
>> To unsubscribe, go to
>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
>> and follow the instructions there.
>> 
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe, go to 
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.


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Re: [time-nuts] A simple sampling DMTD

[Jan-Derk Bakker via time-nuts]

Dear Attila,

Thanks for the heads up.

I am currently using a HPF both in hardware (capacitive coupling into the
balun driving the ADC inputs) and in software before the ZCD. This should
counteract the first-order effects of this offset, although second-order
effects (converter nonlinearity et al) will of course still be an issue.
The plots you've quoted include (different kinds of) DC offset correction
for all but the "unfiltered" data; getting an efficient DC offset
correction working in real time on this 8-bit platform was indeed one of
the main challenges of the software-only approach.

The FPGA daughterboard is currently in production at Eurocircuits; I hope
to have time to work on those the coming month. I'll also try to book some
time in our climate chamber. (I've had one of our GPSDO-designs running in
our general labs since before Christmas; surrounding it with bottles of
water works well enough to low pass filter temperature swings, but I still
see 6 degrees C swings overnight as out HVAC only runs during business
hours.)

To be continued,

JDB.

On Sun, Feb 23, 2020 at 8:11 PM Attila Kinali via time-nuts <
time-nuts@lists.febo.com> wrote:

> Good evening!
>
> I'm going through some old stuff...
>
>
> On Wed, 27 Nov 2019 00:29:19 +0100
> Jan-Derk Bakker  wrote:
>
> > This has yielded a combined "simple" signal
> > processing path of a differentiator, a double comb filter and the offset
> > estimator, which is getting very close in performance to the "ideal" band
> > pass filter (OADEV of 3.77e-13@tau=1s versus 3.25e-13@tau=1s for the
> BPF;
> > full plot:
> >
> http://www.lartmaker.nl/time-nuts/DMTD%20self-noise%20OADEV%20with%20PLL%20and%20various%20filters.pdf
> > for this 60-second recording:
> >
> http://www.lartmaker.nl/time-nuts/600ksec%20run%20with%20PLL,%2010811%20through%20splitter.png
> > . OADEV past ~1000sec is severely compromised by the fact that the
> > measurement setup is in my home lab which sees temperature swings of up
> to
> > 20 degrees C and which does get bumped from time to time. Longer runs in
> a
> > more controlled setting forthcoming).
>
>
> I can offer an explanation for the large effect of the zero correction seen
> here. The LTC2140 is specified to have a +/-10µV/°C drift (at 1Vpp
> setting).
> Converted into phase error due to zero crossing shift, this turns into
> a phase shift of +/-1ps/°C @ 10MHz. Note, the shift is given as +/- and
> per channel, which means, it could very well be that the channels are
> not matched in their temperature characteristics and thus the total phase
> shift could be +/-2ps/°C ... though total shift being closer to 0.5ps/°C is
> more likely.
>
> Summa sumarum: DC offset correction is important if a zero crossing
> detector is used.
>
> Attila Kinali
>
> --
> The bad part of Zurich is where the degenerates
> throw DARK chocolate at you.
>
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
>
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Re: [time-nuts] A simple sampling DMTD

[Attila Kinali via time-nuts]

On Sun, 23 Feb 2020 14:19:20 -0500
Bob kb8tq via time-nuts  wrote:

> Since most mixers also have DC offset issues, it is pretty common to high 
> pass filter 
> the signal before you try to hit a limiter.  Yes, this can bring in other 
> issues, but the
> net result is commonly a “win”. 

With a discrete DMTD system, I would recommend using a feedback
circuit that ensures the output has 50% duty cycle. This both
compensates for the offset from the mixer and offset in the
squaring circuit. It also has the advantage of keeping the
even mode harmonics low and thus the folding of 1/f noise
is limited (or even eliminated).

Also keep in mind that Collins overestimates the noise
contributions for amplifiers with low gain. Ie the optimum
gain for the first stages is higher than Collins formula
suggests.

Attila Kinali

-- 
The bad part of Zurich is where the degenerates
throw DARK chocolate at you.

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Re: [time-nuts] A simple sampling DMTD

[Bob kb8tq via time-nuts]

Hi

Since most mixers also have DC offset issues, it is pretty common to high pass 
filter 
the signal before you try to hit a limiter.  Yes, this can bring in other 
issues, but the
net result is commonly a “win”. 

Bob


> On Feb 23, 2020, at 2:10 PM, Attila Kinali via time-nuts 
>  wrote:
> 
> Good evening!
> 
> I'm going through some old stuff...
> 
> 
> On Wed, 27 Nov 2019 00:29:19 +0100
> Jan-Derk Bakker  wrote:
> 
>> This has yielded a combined "simple" signal
>> processing path of a differentiator, a double comb filter and the offset
>> estimator, which is getting very close in performance to the "ideal" band
>> pass filter (OADEV of 3.77e-13@tau=1s versus 3.25e-13@tau=1s for the BPF;
>> full plot:
>> http://www.lartmaker.nl/time-nuts/DMTD%20self-noise%20OADEV%20with%20PLL%20and%20various%20filters.pdf
>> for this 60-second recording:
>> http://www.lartmaker.nl/time-nuts/600ksec%20run%20with%20PLL,%2010811%20through%20splitter.png
>> . OADEV past ~1000sec is severely compromised by the fact that the
>> measurement setup is in my home lab which sees temperature swings of up to
>> 20 degrees C and which does get bumped from time to time. Longer runs in a
>> more controlled setting forthcoming).
> 
> 
> I can offer an explanation for the large effect of the zero correction seen
> here. The LTC2140 is specified to have a +/-10µV/°C drift (at 1Vpp setting).
> Converted into phase error due to zero crossing shift, this turns into
> a phase shift of +/-1ps/°C @ 10MHz. Note, the shift is given as +/- and
> per channel, which means, it could very well be that the channels are
> not matched in their temperature characteristics and thus the total phase
> shift could be +/-2ps/°C ... though total shift being closer to 0.5ps/°C is
> more likely.
> 
> Summa sumarum: DC offset correction is important if a zero crossing
> detector is used.
> 
>   Attila Kinali
> 
> -- 
>   The bad part of Zurich is where the degenerates
>throw DARK chocolate at you.
> 
> ___
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe, go to 
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.


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Re: [time-nuts] A simple sampling DMTD

[Attila Kinali via time-nuts]

Good evening!

I'm going through some old stuff...


On Wed, 27 Nov 2019 00:29:19 +0100
Jan-Derk Bakker  wrote:

> This has yielded a combined "simple" signal
> processing path of a differentiator, a double comb filter and the offset
> estimator, which is getting very close in performance to the "ideal" band
> pass filter (OADEV of 3.77e-13@tau=1s versus 3.25e-13@tau=1s for the BPF;
> full plot:
> http://www.lartmaker.nl/time-nuts/DMTD%20self-noise%20OADEV%20with%20PLL%20and%20various%20filters.pdf
> for this 60-second recording:
> http://www.lartmaker.nl/time-nuts/600ksec%20run%20with%20PLL,%2010811%20through%20splitter.png
> . OADEV past ~1000sec is severely compromised by the fact that the
> measurement setup is in my home lab which sees temperature swings of up to
> 20 degrees C and which does get bumped from time to time. Longer runs in a
> more controlled setting forthcoming).


I can offer an explanation for the large effect of the zero correction seen
here. The LTC2140 is specified to have a +/-10µV/°C drift (at 1Vpp setting).
Converted into phase error due to zero crossing shift, this turns into
a phase shift of +/-1ps/°C @ 10MHz. Note, the shift is given as +/- and
per channel, which means, it could very well be that the channels are
not matched in their temperature characteristics and thus the total phase
shift could be +/-2ps/°C ... though total shift being closer to 0.5ps/°C is
more likely.

Summa sumarum: DC offset correction is important if a zero crossing
detector is used.

Attila Kinali

-- 
The bad part of Zurich is where the degenerates
throw DARK chocolate at you.

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