[time-nuts] How to get 32.768KHz from 10MHz.

Bruce Griffiths bruce.griffiths at xtra.co.nz
Wed Jul 23 19:19:50 EDT 2008


An oscillator can be injection locked to at frequency that is a rational 
number (M/N where M, N are integers ) multiplier of the injection frequency.
Thus, in principle, a 32768Hz oscillator can be injection locked 
directly to a 10MHz signal (32768Hz = (256/78125)*10MHz) without 
requiring any external dividers or multipliers.
In practice this will only be practical with a 32768Hz crystal 
oscillator whose frequency determining crystal is tuned sufficiently 
closely to 32768Hz.
Note this is not quite the same as tuning the free running oscillator 
frequency.
The sensitivity to the injected signal can be optimised if the 32768Hz 
oscillator is suitably designed.

The 32768Hz injection locked oscillator output can be used to injection 
lock another 32768Hz crystal oscillator whose design cannot be optimised 
for direct injection locking to a 10MHz signal.

Bruce




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