There is one chip(ad9467-250) on my board. This is my scenario: the sampling frequecy is about 180MHz,the IF is about 140MHz, SFDR is about 90dB, IMD is more than 80dB. But when the sampling frequecy is 210MHz and IF is 330MHz, I found SFDR is less than 80dB and IMD less than 70dB. Do you think this is normal? Could you please tell me how to increase the SFDR and IMD when the IF is higher.