Direct digital synthesis (DDS) is a technique to produce an analog waveform (square, triangular, or sinusoidal) by generating a digital time varying signal using an external clock and then passing this digital signal through a digital-to-analog converter. A DDS device offers wideband operation, fast switching between output frequencies and fine frequency resolution. 

DDS devices are ideal for advanced digital modulation techniques like frequency shift keying (FSK), interference mitigation techniques such as frequency hopping and spread spectrum as it allows a nearly instantaneous change in frequency or phase, thanks to its digital programmability. These devices are replacing the traditional phase locked loops (PLLs) and other analog RF sources, as they offer high stability and signal purity.

The main components of a DDS device are: phase accumulator, phase-to-amplitude converter, reference-clock and a DAC. The frequency of the output waveform depends on the reference clock frequency.

A DDS can generate the square, triangular, or sinusoidal Output.