A direct digital frequency synthesizer based on a new form of polynomial approximations

A new form of polynomial approximations of the discrete sinusoid waveform is proposed for the design of a direct digital frequency synthesizer (DDFS). With the polynomial approximation, only square circuits are needed for the DDFS realization, which will tremendously reduce the chip area, and a spurious free dynamic range (SFDR) of more than 95 dBc can be achieved. Based on the approximation, the DDFS circuit is designed and validated via simulations with the TSMC 0.18 μm cell-library.