ADL5391 multiplier problem


I am testing my new ADL5391-Evaluationboard, and coming across with the following problem. As you can see on the figures, the multiplication output is somehow disturbed. The output is not a proper sine-function anymore. Some peaks are higher, some smaller.  It seems that the two input sin/cos-functions internally get some DC before multiplication. I use the board in single-ended mode, so I added an 56Ohm resistor for R2. Any ideas how to fix this problem?


Best regards,


Squaring result of sine-function  

Squaring result of rect-function