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Crystal Reference Oscillator Design - RF Cafe Forums

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Post subject: Crystal Reference Oscillator Design. Posted: Sun Oct 21, 2007 3:25 am


Joined: Tue Feb 27, 2007 6:16 am

Posts: 46


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.

If 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 suitable.

FYI my channel width is 25kHz, Im using National's LMx2346. Thankyou

Regards Darcy Randall, Perth, Western Australia


Regards, Darcy Randall, Perth, Western Australia



Post subject: Posted: Sun Oct 21, 2007 5:14 am

Site Admin

Joined: Mon Jun 27, 2005 2:02 pm

Posts: 373

Location: Germany

Hello Darcy,

Your calculation is correct.

For such a tough spec as you have a simple Crystal is not good enough.

You should 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

Posts: 46

Legend. Thankyou


Regards, Darcy Randall, Perth, Western Australia

Posted  11/12/2012

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