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Re: really bad oscillators

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On 10/07/2018 11:05 AM, John Larkin wrote:
> On Sat, 6 Oct 2018 21:59:11 -0400, bitrex <user@example.net> wrote:
> 
>> On 10/06/2018 01:33 PM, John Larkin wrote:
>>>
>>>
>>> A timestamper is a circuit that latches the time of arrival of a pulse
>>> edge. We use a clock and a binary counter as MC, the master counter
>>> definition of time. We extend those MC bits down into picoseconds with
>>> a time interpolator, adding 8 to 12 bits below the counter LSB.
>>>
>>> One way to test a time stamper is to stamp pulses that are random in
>>> time, and then histogram/analyze the codes. That can catch all sorts
>>> of nasties, like stuck or shorted bits or interpolator problems; we've
>>> done the math on that. In the test set that I'm designing, I want a
>>> simple but really bad pulse generator, maybe around 1 MHz with tons of
>>> period jitter, to get good statistics and never alias against the
>>> master clock. Aliasing can make really weird histograms.
>>>
>>> https://www.dropbox.com/s/vv6dqeffxrkmca3/Timestamp_Noisy_Osc.jpg?raw=1
>>>
>>> The single inverting schmitt oscillator is probably good enough, but
>>> it's fun to consider other really nasty oscillators. A bad power
>>> supply will only help.
>>>
>>> We have an FPGA, so I guess we could build a pseudorandom bit stream,
>>> filter that a little, and use that to confuse a schmitt oscillator.
>>> The kids might enjoy programming that.
>>>
>>>
>>
>> Chua's circuit is the textbook chaotic oscillator:
>>
>> <https://en.wikipedia.org/wiki/Chua%27s_circuit>
> 
> It's chaotic but it still has strong periodicties, and would probably
> alias against my clock.
> 
>>
>> Adding a single capacitor to the usual "blocking oscillator" can make a
>> chaotic oscillator:
>>
>> "The output signal of such chaotic oscillator is a series of short term
>> pulses characterized by chaotic fluctuations of time intervals between
>> pulses. Such chaotic pulse signals possess a broad-band continuous power
>> spectrum and short correlation length."
>>
>> (PDF) Generation of broad-band chaos using blocking oscillator.
>> Available from:
>> <https://www.researchgate.net/publication/3323718_Generation_of_broad-band_chaos_using_blocking_oscillator>
>>
> 
> Right. A blocking oscilllator is like a super-regen receiver in that,
> if the time constants are right, the period is dominated by noise.
> 
>> Two sheet-beam tube oscillators, each configured as self-oscillating
>> singly-balanced mixers, cross coupled to each other would probably make
>> a pretty crappy oscillator
> 
> Again, in my application, I want the oscillator periods to be jitterey
> at all time scales. I want "the spectrum of the jitter" to be
> broadband so it doesn't correlate with any periodic clock.
> 
> I wish I knew more about the TPS54302 spread-spectrum mechanism. I'll
> have one on my board, so that noise is free.
> 
> https://www.dropbox.com/s/s9aqx1z3glab423/TPS54302_PWM.JPG?raw=1

This gentlemen made a random-bit generator just from abusing the race 
conditions that can naturally occur in multi-core, multi-threaded 
processors where resource access is not properly synchronized between 
code in different threads of execution, kinda interesting!

<https://groups.google.com/forum/#!topic/comp.lang.c++/7u_rLgQe86k/discussion>

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really bad oscillators John Larkin <jjlarkin@highlandtechnology.com> - 2018-10-06 10:33 -0700
  Re: really bad oscillators "Tim Williams" <tiwill@seventransistorlabs.com> - 2018-10-06 12:51 -0500
    Re: really bad oscillators whit3rd <whit3rd@gmail.com> - 2018-10-06 15:16 -0700
      Re: really bad oscillators John Larkin <jjlarkin@highlandtechnology.com> - 2018-10-06 15:52 -0700
      Re: really bad oscillators "Tim Williams" <tiwill@seventransistorlabs.com> - 2018-10-06 22:55 -0500
  Re: really bad oscillators George Herold <gherold@teachspin.com> - 2018-10-06 11:33 -0700
  Re: really bad oscillators John Larkin <jjlarkin@highlandtechnology.com> - 2018-10-06 11:35 -0700
  Re: really bad oscillators <698839253X6D445TD@nospam.org> - 2018-10-06 18:49 +0000
  Re: really bad oscillators Steve Wilson <9fe142ac@gmail.com> - 2018-10-06 11:50 -0700
  Re: really bad oscillators bloggs.fredbloggs.fred@gmail.com - 2018-10-06 12:13 -0700
    Re: really bad oscillators John Larkin <jjlarkin@highlandtechnology.com> - 2018-10-06 15:55 -0700
  Re: really bad oscillators Gerhard Hoffmann <ghf@hoffmann-hochfrequenz.de> - 2018-10-06 21:28 +0200
    Re: really bad oscillators Gerhard Hoffmann <ghf@hoffmann-hochfrequenz.de> - 2018-10-06 21:35 +0200
    Re: really bad oscillators John Larkin <jjlarkin@highlandtechnology.com> - 2018-10-06 16:01 -0700
  Re: really bad oscillators bitrex <user@example.net> - 2018-10-06 21:59 -0400
    Re: really bad oscillators John Larkin <jjlarkin@highlandtechnology.com> - 2018-10-07 08:05 -0700
      Re: really bad oscillators bitrex <user@example.net> - 2018-10-07 23:04 -0400
        Re: really bad oscillators John Larkin <jjlarkin@highlandtechnology.com> - 2018-10-07 21:10 -0700
      Re: really bad oscillators bitrex <user@example.net> - 2018-10-07 23:12 -0400

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