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Question about clock design in AD-FMCOMMS1-EBZ design

Question asked by Matt1012 on Mar 17, 2016
Latest reply on Mar 22, 2016 by charlyelkhoury

Hi,

I have two questions regarding the clock design in AD-FMCOMMS1-EBZ design:

1) Is there any benefit to program the AD9523-1 Frequency output with 122.88MHz to both TX & RX LO (the lowest input is 10MHz),

   Shall be able to use 30.72MHz. (in which fPFD=REFIN). Is it because better phase noise or other concern.

   I have tried the ADIsimPLL tool, and running the simulation, but I got worse VCO phase noise using 122.88MHz reference input     

    (compared with 30.72MHz reference input. )

2) AD9548 was used here with 30.72MHz clock input from FPGA board.

   I suppose the 30.72MHz clock could be directly connected to 9523-1 low-jitter cock distributor.

   Is there any reason to use this ? (jitter cleanup to have clean clock output to ADC &DAC? )


Please advise,


Thanks.

Matt

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