[time-nuts] Low noise PLL for transceiver locking

Murray Greenman Murray.Greenman at rakon.com
Tue Feb 2 18:14:55 UTC 2010


Frank,

My suggestion would be to try injection locking, rather than a PLL. No
change is made to the 22MHz and 42MHz oscillators, except to find a way
to inject enough reference power to force them to lock to it. Injection
locking works well with modest harmonic relationships, and gives good
noise performance. The injection can be via a coupling link, or even at
the cold end of an existing bypass capacitor. Narrow pulses often work
best.

I am confident that you could lock 22MHz to a 2MHz injection (divided
from your 10MHz reference) if the 2MHz pulse was narrow enough and the
22MHz oscillator sufficiently stable. 42MHz is more of a challenge - you
might need a double-step, such as first locking 7MHz to 1MHz from the
reference, and using that to lock 42MHz.

The literature on injection locked oscillators is quite limited.  You
get very interesting results as the lock drops out!

73,
Murray ZL1BPU






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