Our application is DVB-C modulator,
The chip set adopted includes ADF4360-2, ADCLK-914 and AD9789.
We have a problem of bad RF quality for QAM-128 and QAM-256.
It looks fine when the constellation is QAM-64.
The situation is getting worse once the constellation and channel frequency go higher.
I am wondering if the clock quality of ADF4360-2 is not good enough to support QAM-128 and QAM-256.
Please provide some suggest.