LMX2595: The reference signal passing through the LMX2595 generates spurious signals at integer multiples of the reference frequency.

Hello,  I observed a phenomenon that puzzled me.

When my LMX2592's reference signal is set to 125MHz, there is a strong 3.5GHz spurious output. Also, when I tested with a trial version of LMX2595, using 125MHz reference provided by SMW200A, I observed the same phenomenon. It's preliminarily determined that this spurious signal is generated by the PLL. Can this spurious signal be eliminated or reduced?