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eran Post subject: Synchronizing two crystal oscillators Posted:
Sat Nov 24, 2007 3:26 am Lieutenant Joined: Fri Nov
23, 2007 11:59 am Posts: 4 Location: Israel Hi Guys, I
have xo for my VSAT tuner, and I'm currently designing the LO for my
burst receiver (direct conversion). Problem: I have to use the tuner
crystal oscillator, (synchronous LO's) but the main xo is located "miles"
away from my LO, and it passes through LVDS. The phase noise performance
is awful: (-105dBc/Hz @1KHz) and I must use a local reference oscillator!!!(I
need -35dBc integrated noise, with settling time of roughly 100us. I
use a broad band VCO so it includes an active loop filter) I was
thinking to use a close by VCXO, and synchronize it with the main xo.
Question: What is the simple, cost effective way to implement such
a synchronization loop (pll, costas)? Your help will be highly appreciated,
Regards, Eran. Top Feng Post subject:
Posted: Sun Nov 25, 2007 3:07 am Captain Joined:
Sun Mar 19, 2006 5:25 pm Posts: 21 Location: Burnaby Hi Eran,
You may think about using GPS modules to synchronize them. A
general GPS module can provide quite precise clock signal. Working with
a VCXO, both the short term stability and long term stability can be
achieved at the same time. Hope it is little helpful.
Top eran Post subject: GPS module is overkillPosted:
Mon Nov 26, 2007 3:31 am Lieutenant Joined: Fri Nov
23, 2007 11:59 am Posts: 4 Location: Israel I was thinking
using a phase detector and vcxo at the same xo refference frequebcy(no
prescaler is needed) and simply close a loop on the vcxo. I only
need to check the influance of the delay time, but as for the phase
lock i think it will work.don't you think? Top eran
Post subject: Has anyone done it before?Posted: Sun Dec 02, 2007
3:32 am Lieutenant Joined: Fri Nov 23, 2007 11:59
am Posts: 4 Location: Israel did anyone implemented a sync.
of two oscillators,and have comments? Top nubbage
Post subject: Posted: Mon Dec 03, 2007 8:04 am General
Joined: Fri Feb 17, 2006 12:07 pm Posts: 218 Location:
London UK Hi Eran This is a comment requirement for the design
of SONET/SDH multiplexers, where the synch clock is extracted from the
data stream. If that should become corrupted or the link broken, the
mux is required to free-run on its own internal TCXO, then re-synch
when the stream is re-established. For that function the TXCO is continuously
synched to the stream if it is there. I have not seen the circuits
that achieve this, but I guess there must be refs on the web to how
it is done. Try a search engine with some key words like SONET, SDH
and "clock". Posted 11/12/2012
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