A 100 MHz DDS with synchronous oscillator-based phase interpolator

A synchronous oscillator-based phase interpolator is used to lower spurious tones of a 100 MHz 16 b DDS. The synchronous oscillator locked-loop produces an eight-phase clock with coarse phase interpolation, while eight identical oscillators coupled with a DAC provide accurate phase adjustment. Spurious tone reduction obtained with the accurate phase interpolation is about 20 dB.