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How to solve ADF435 spur?

Question asked by qingyawar on Jul 30, 2017

Hello  ,

I  was thinking of using the ADF4351 at 200M~300M.

The 200M~300MHz signal is generated using ADF4351, the frequency interval is 1KHz, and the register configuration is shown as shown,

Set the MOD constant to 1250 due to turn on low spur mode.

The loop filter ADF4351 is designed using ADIsimPLL, using fast locking mode, and the design results are as follows

Frequency domain phase noise

The loop filter parameter is as follows

The 10M crystal is not stable, so the input reference signal provided by the RF source 10MHz, 1V input.

the final test results: the output frequency is 271.2MHz proximal (4.765KHz and 317Hz) are spur, don't know how to eliminate the spurious, seeking advice.

Many thanks.