A low-complexity direct digital frequency synthesizer
Lai Linhui, Li Xiao-jin, Lai Zong-sheng · 2008
The traditional direct digital frequency synthesizer (DDFS) based on a lookup table has very high complexity. This paper describes a low complexity DDFS using smaller lookup table and with minimum additional hardware. The lookup table for sine/cosine functions is split into a coarse-precision ROM and a fine-precision ROM. Approximation of fine-precision ROM and application of shift registers are introduced to further reduce the hardware complexity. The implemental results show that the total size of ROM in this proposed DDFS architecture is only 328 bits compared with 448 bits in [1], and the spectral purity can be as good as 63.58 dBc.