AD9361 low frequency spurious

Hello everyone!

i find there are some low frequency spurious on my AD9361's TX port，when i send a BIST on 2.4GHz , it looks like this:

disable the BIST , the output looks like this：

when i change the TX LO frequency and the BBPLL frequency ,the Low frequency spurious will have some change like this:

How can i solve this problem?

THANKS!