I have a problem about the output signal spectrum about the QUDC of AD9957 . My output frequency is in the 280MHz range so my SYS_CLK is currently set to 960MHz. Assuming I set the interpolation factor rate to 50, my PDCLK frequency is 9.6MHz. When I set the Parallel Data I and Q vectors by "000000000000000000" and "011111111111111111", I think I would get a single tone signal. While, the signal spectrum I got is this(see the picture in the Attachment ), I'm confused about this. Some other modulated signals I generated also have this problem. I need your help.