LMX2594: The output signal is surrounded by many interference signals with equal spacing

Hi team,

Configure the LMX2594 output 2GHz dot frequency, reference signal 50MHz, phase detector frequency 100MHz, output spectrum as shown in Figure 1, Near the carrier high interference occurs at 2.56 MHz intervals, MUXOUT pin set high.

What are the possible causes of this phenomenon? How can eliminate this interference?

Thanks,

Amy Luo