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ADF4360-9 for generating a LO freq. Unacceptable Jitter?

Question asked by bmackenzie on Jan 13, 2011
Latest reply on Jan 27, 2011 by aharney

Hello,

 

A somewhat basic concept is causing me a lot of confusion.

 

It is my intention to use an ADF4360-9 for synthesizing a LO freqeuncy to be used in downconverting a digital C4FM RF signal. For reference, my LO frequency must be between 25 and 45MHz for channel selectivity.

 

It is clear to me that the ADF4360-9 is cabile of producing frequencies in this range so long as its auxillary divider is in use. However, I am concerned by the jitter that is inherently produced. The datasheet depicts that typical jitter at within my frequency range is approximately 1.4picoseconds.

 

The C4FM modulation scheme encodes symbols at +/-600Hz, and +/-1800Hz from the center frequency. If my synthesized LO frequency has a jitter of 1.4ps, won't some of my symbols be undistinguishable from the jitter that is occuring "naturally" in my LO frequency?

 

- What is the solution to this problem? Do I pick a device that synthesizes my LO frequencies stable enough not to mask the +/- 600Hz variance in frequency that could be occuring due to modulation?

 

- Does Analog Devices have a product that fulfills my needs?

 

- Instead, should I use PLL driven with a VCXO tha's then connected to an external VCO for synthesizing my LO frequency? Or, something similar?

 

Am I even thinking about this problem correctly?

 

I appreciate the help.

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