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ADF5355 +/-10kHz & +/-20kHz offset spurious

Question asked by AkiraO on Jul 23, 2018



I received a question about +/-10kHz and +/-20kHz offset spurious of ADF5355 from our customer.

When he set to output frequency at 12.05GHz, the output has +/-10kHz and +/-20kHz offset spurious. Plese refer following picture.

REF=50MHz, and regster setting are followings;

Register0       0x00200780

Register1       0x08000001

Register2       0x00000012

Register3       0x00000003

Register4       0x30009D84

Register5       0x00800025

Register6       0x3502A006

Register7       0x120000E7

Register8       0x102D0428

Register9       0x15153CC9

Register10      0x00C01F7A

Register11      0x0061300B

Register12      0x0001041C

On the other hand, the customer set t output frequency at 12.050004GHz, 12.1499GHz, 12.3498GHz, 12.3497GHz and so on, there are no spurious.

Then, the customer changed MOD2 setting for getting 12.05GHz output frequency. But he can see the spurious when output frequency is 12.05GHz.


Do you have any ideas about a cause of the spurious and how to improve it?


Best regards,