AD9634 digital signal rippling interference

Hi, I am using AD9634.When I use the test mode and use ramp out,  I observed some glitches. as shown in the first feagure.

then I use a oscilloscope to check the digital signals, I I observed that, the digital signal from the scope looks wierd. it is supposed to be a square wave. but there are strong rippling interference there.

Can anyone help analyze what is the issue?

Thanks