A pipelined ROM-less architecture for sine-output direct digitalfrequency synthesizers using the second-order parabolic approximation

摘要

A mathematical approximation for the sine function is proposednwhich is so close to the sine function that it satisfies the accuracynrequirements for sine computation in a typical sine-output directndigital frequency synthesizers (DDS). Then, it is shown that thenproposed approximation is realizable by standard digital circuitry, so,na novel ROM-less architecture for sine-output DDS is developed,noptimized, and implemented. Experimental results for the implementednROM-less sine-output DDS are in complete agreement with simulationnresults in showing that the approximation error will cause harmonicnlevels below the spurious levels associated with the output quantizationnerror. Another important advantage of the proposed architecture is thatnit dispenses with ROM, so it can be easily pipelined in order to be asnfast as is required