[sdiy] square to sine

[cheater cheater]

Right, I was wondering how similar that is to a PLL. I haven't seen
the equivalence mentioned yet, though.

D.

On Thu, Oct 11, 2012 at 4:38 AM, Neil Johnson
<neil.johnson97 at ntlworld.com> wrote:
> Hi,
>
> cheater cheater wrote:
>> Dave, I'm going out on a limb here, but this reminds me of a technique
>> normally used for asynchronous sample rate conversion, which is
>> "flywheel sync".
>
> "flywheel synchronisation" was an early term for the then-new
> technique of PLL as used in British TV sets:
>
> http://en.wikipedia.org/wiki/Broadcast_television_systems#Image_polarity
>
> and later used for the 4.something MHz colour burst.
>
> A blast from the past: BBC R&D report from 1969 talks about flywheel
> synchronisation:
>
> http://downloads.bbc.co.uk/rd/pubs/reports/1969-44.pdf
>
> The diagram on page 2 of the report is a PLL.
>
>> Basically, you have a model of a flywheel - with
>> torque and friction - and each rotation of it is one output wave
>> cycle. As clocks come in, you give the flywheel a "push" or "jolt". If
>> the jolts stop coming in, the flywheel stops eventually. If they come
>> in at a lower frequency, the flywheel spins slower. If you rapidly
>> lower the frequency, you can add some friction (for example, friction
>> gets -df/dt added to it). It is normally used to prevent jitter, but
>> can also be used for syncing two different waveforms together.
>
> You're talking about the characteristics of the various components of
> the PLL (vco, phase detector, loop filter, etc).
>
> Cheers,
> Neil
> --
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> Homepage: http://www.njohnson.co.uk