I am using AD9959 evaluation board to generate my signal. However, the output of the DDS board is not perfectly sinusoidal for frequencies lower than 1/4th the system clock frequency. Is this generic to DDS frequency generators?
Following are the oscilloscope traces.
The board is being clocked by a 10Mhz signal generator
Yellow->DDS output, Blue->Clock signal
With clock multiplier disabled for an output of 0.5MHz.
With clock multiplier disabled for output 2Mhz.
With clock multiplier 10 for output 2 Mhz