Clarification regarding connecting the output to spectrum

Hi Team,

Greetings!

We are using the board for R&D purpose before we use the HMC7043LP7FE IC in our custom design. We want to connect the output of evaluation board to spectrum analyzer to evaluate the performance of the IC.

We selected the output to be CMOS in GUI and connected CLKOUT0_P to spectrum analyzer and terminated CLKOUT0_N with 50 ohm terminator. We observed a lot of harmonics in the spectrum analyzer. Below attached image for your reference.

Please let us know if this is an expected result or are we missing out anything when we are connecting output to the spectrum.

The configuration done in GUI is attached below for your reference 

Thanks in Advance :-),

Anu M K