ROM-less DDFS using non-equal division parabolic polynomial interpolation method
Chia-Hao Hsu, Yun‐Chi Chen, Chua‐Chin Wang · 2011
A direct digital frequency synthesizer (DDFS) based on a non-equal division parabolic polynomial interpolation method is proposed in this paper. To attain high spurious free dynamic range (SDRF) and reduce area cost, a parabolic polynomial interpolation method is adopted in the proposed design to replace conventional ROM-based phase-to-sine mapper methods. Particularly, the left 1/4 of the phase range is approximated using a low-curvature parabolic curve. The proposed design is manufactured using a standard 0.18 μm CMOS technology. The maximum output frequency is 50 MHz, the core area is 1.4528 mm2, and the spurious free dynamic range (SFDR) is 68.67 dBc. The proposed DDFS outperforms prior works' SFDR and energy efficiency.