What layout recommendations do you have for the power supply pins of the DDS device?

It is important that all supply pins (GND, AVDD, DVDD) connect to their respective GND or POWER plane with the shortest amount of trace length. This will reduce the total series inductance.

Equally important is to connect bypass chip-capacitors as close as possible to each and every power pin. Typically, we recommend 0.01µF for these capacitors. This will provide a good AC ground at the power pins for higher frequencies in order to minimize noise coupling from the part to the power supply rail, and vice versa.