Novel Approach to Designing Quadrature Direct Digital Frequency Synthesizer
Meng Li · 2010
A decomposition method for parabolic polynomial approximation was proposed to improve spurious free dynamic range(SFDR) of quadrature DDFS(Direct Digital Frequency Synthesizer) and decrease logic element occupancy. In this technique,sine(cosine) function was decomposed into several correlation functions,which was then calculated by using quadratic polynomial approximation.Compared to the conventional quadratic polynomial approximation, the proposed method could achieve a higher SFDR(up to 99.3 dBc) and a 20%reduction of logic element occupancy.Simulation results showed that,in high spectral quadrature-DDFS design,the proposed method is significantly superior in hardware cost,compared with the conventional approach.