We tested ADF5610 evaluation board using external low phase noise OCXO and we observed spurious frequencies around 10KHz. I attached the test results & settings done in GUI.
External Reference: 120MHz,
RF Output frequency: 13.58GHz
There is no spur in the phase noise graph provided by you in above reply..
So We gave External reference (100MHz, 80MHz, & 50MHz) using signal generator and observed more variations in the spurious frequencies while varying external reference (R divider kept constantly =1). I also attached some results.
Please suggest any method to reduce these spurs.
Pathu said:There is no spur in the phase noise graph provided by you in above reply..
Which result above was provided by ADI?
I forgot to mention the link. Please find the data provided by ADI in below link
The results that we provided were for integer frequencies. At fractional frequencies there may be spurious tones seen that are not seen at integer frequencies. You can try adjusting the CP current in order reduce the spurs seen. You can also refer to 'Charge Pump Phase Offset' in the datasheet. Adding a phase offset can help to improve performance.
I tried for integer frequencies also and I got same response in spurious rejections.
I already applied full charge pump current offset and there was no much difference in spurious rejection but reducing the offset leads to phase noise degradation.
For my application fractional mode is mandatory requirement, So please test & provide the spurious data for the below frequencies without degradation in phase noise.
1) RF output: 14550MHz, Ref input : 100MHz (Fractional mode)
2) RF output: 14500MHz, Ref input: 100MHz (Integer mode)
Here are the results you requested. Configured with Loop filter described in the other question you posted.
I do not see the same spurs using the R&S SMA100B. Please check your power supplies and reference configuration.