Crystal Reference Oscillator Design - RF Cafe Forums
Post subject: Crystal Reference Oscillator
Design. Posted: Sun Oct 21, 2007 3:25 am
Joined: Tue Feb 27, 2007 6:16 am
For the sake of learning and my own interest, I have been designing
a UHF data radio.
Is this correct ?
If my carrier freq
is 450.325MHz accurate to +/-200Hz
Lets say Im using a 20MHz
Crystal reference oscillator for my PLL.
Then a rough calculation
tells me that my crystal must be accurate to within -> 20*PPM*(450.325*10^6)/(20*10^6) <
200 -> 0.44PPM.
Where PPM is parts per million.
these calculations are correct, can anyone recommend where I can
find a crystal reference ocillator with a TTL or CMOS output, accurate
to 0.44PPM? I believe an oscillator from 5MHz to 25MHz would be
FYI my channel width is 25kHz, Im using National's
Regards Darcy Randall, Perth, Western
Regards, Darcy Randall, Perth,
Post subject: Posted:
Sun Oct 21, 2007 5:14 am
Jun 27, 2005 2:02 pm
Your calculation is correct.
For such a tough
spec as you have a simple Crystal is not good enough.
use a TCXO. I found an example for one with 0.28PPM and a CMOS output:
http://www.valpeyfisher.com/openlink.as ... FTX160.pdf
You can also ask for samples and define the frequeny that
you need. Please contact the manufacturer for further help.
Post subject: Posted: Sun
Oct 21, 2007 9:03 pm
Joined: Tue Feb
27, 2007 6:16 am
Regards, Darcy Randall, Perth, Western Australia