[time-nuts] Re: DMTD and TICC with YimeLab question

[Bob kb8tq]

Hi

If you head back into the archives and search for “Collins Limiter” ( hopefully spelled 
correctly ) you will find a whole bunch of info on attempting to convert low frequency
sine waves to fast edge square waves. It suggests that the “SNR” needs to be managed
against the slew rate through a number of stages to do things well. 

There are a lot of designs out there that don’t use the Collins approach. There also are
papers from various well known folks calling into question some of the basic assumptions
made in the paper. Possibly somebody will chime in with links to a range of papers.

Bottom line is that you are doing well to get a net of 1x10^-13 out of a system like this. 
Getting to 1x10^-14 at one second seems to be out of range for whatever reason. 

Bob

> On Nov 25, 2022, at 6:39 AM, Erik Kaashoek via time-nuts <time-nuts at lists.febo.com> wrote:
> 
> All,
> What would the SNR of the input to the TICC have to be to have a no noise in the zero crossing when the time has been stretched by a factor 1e6?
> 1e6 calculates to 120 dB, 1e17 to 320 dB
> Is that a problem when cascading a DMTD and a TICC?
> Erik.
> 
> On 25-11-2022 11:51, Tom Van Baak via time-nuts wrote:
>> Skip,
>> 
>> Most programming languages and computer software, including Stable32 and TimeLab, use an ascii computer form of scientific notation with an E in it (lower case e is ok too). So 1 million is 1e6, or 1000e3 or 1000000. 2048 is 2.048e3, and so on. If in doubt use Excel or Python or a calculator app to compute 1000 × 1000 and it should show 1e6 or 1.0e6 or maybe 1 × 10^6 or 1.00 × 10^6. So that's the off-by-ten problem you are having. For a million write 1E6, not 10E6. What you wrote, 10E6, is ten million.
>> 
>> When you see the E, read it out loud as "times ten to the power". So 1.23E6 is 1 point 2 3 times 10 to the power 6.
>> 
>> I used to nudge members to correct their postings where E-format scientific notation was misused, or Allan was misspelled Allen, or when 10 MHz was written 10 mhz or 10 Mhz or 10 MHZ, or when ns was spelled nS or nsec or nsecs, but that turned out to be a losing battle over time. In many cases the meaning in context was clear even if what was written was technically incorrect.
>> 
>> On the TICC question, with a DMTD heterodyne factor of one million, which is 1e6, and a resolution of 60 ps, which is 60e-12 or 6e-11 s, the theoretical resolution is 6e-11 / 1e6 = 6e-17 s. You could also call that 60 as (attosecond).
>> 
>> /tvb
>> 
>> 
>> On 11/24/2022 6:45 PM, Skip Withrow via time-nuts wrote:
>>> I have a DMTD front end (based upon the William Wriley design) driving a
>>> TAPR TICC and processing the data with TimeLab.  I just want to make sure
>>> that I understand how all the pieces fit together and that my results are
>>> correct.
>>> 
>>> The input signals are at 10MHz and I am using a 10,000,010 Hz offset
>>> oscillator.
>>> This means that I am getting 10 readings per second and that the input
>>> phase difference should be multiplied by 10E6 (one million).
>>> So, if I feed the same signal into both inputs with one delayed 9ns the
>>> TICC (operated in time difference mode) should give a reading of 9x10E-9 x
>>> 10E6 = 9ms (9x10E-3).
>>> 
>>> Now, to make TimeLab give rational results the TICC difference readings
>>> have to be scaled by the DMTD front end multiplication factor (one
>>> million).  So, in setting up TimeLab the TICC time difference readings need
>>> to be multiplied by 10E-6.  But I think there is a notation problem here -
>>> I represent numbers as
>>> n.n x 10Ey  and I think the TimeLab representation is n.nEy (can anyone
>>> confirm this?).  This makes things very easy to be off by a factor of 10
>>> (the problem I think I am having).
>>> 
>>> Also, the TICC has a resolution of about 60ps.When the DMTD front end is
>>> factored in does this mean that the (theoretical) resolution is 60 x
>>> 10E-18s?  I realize that the noise floor is MUCH higher than this.
>>> 
>>> Thanks for any insights, or putting me on the right track.
>>> 
>>> Skip Withrow
>>> 
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