An efficient direct digital frequency synthesizer based on two-level table lookup

Abstract

This paper proposes a new direct digital frequency synthesizer (DDFS). It has the merits of high speed, low complexity and high spectrum purity [1], [2]. It is based on the Taylor's expansion method for sinusoidal and cosine functions, combined with a two-level table-lookup algorithm. The new DDFS is efficient, with a small table size and low computational complexity. In all, this new DDFS needs three lookup tables, each of size 2(N/4), which is smaller than the other table-lookup methods, such as Madisetti, et al., (of size 2(N/3)) [3], [4]. The DDFS is non-recursive, which is free of error-propagation problem inherently in the recursive DDFS's. For N=16-bits example, simulation shows that the new DDFS has a high SFDR (spurious free dynamic range) of 100 dBc.