[time-nuts] reference oscillator input circuit
jimlux at earthlink.net
Thu Dec 9 13:57:15 UTC 2010
Chris Albertson wrote:
> Of all the ways to "square" a sine wave I think the best might be to use a PLL.
> the raising edge of your output square wave would trigger a sample of the
> input sine wave. The distance from zero volts of that sample is the
> phase error.
> The goal is to have the raising edge of the square wave happen just as the
> sine crosses zero. But if it's not dead-on you get an error signal that can be
> either positive or negative and this error is low pass filtered and
> then applied as
> a correction.
> But my guess is that if you are using this to feed a 'scope a
> reference frequency
> the scope will have it's own PLL.
No, actually to feed a bunch of synthesizer chains (for which the sine
wave will work fine) and to drive sampling clocks on ADC/DAC (for which
one wants a low jitter square wave).
A digital radio...
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