Digital sinusoidal oscillators with high frequency resolution and low harmonic distortion

In this paper, we propose two new techniques to significantly improve the f requency resolution of a digital look-up-table (LUT) tunable sinusoidal osc illator. The proposed techniques are based on storing and reading the sine and cosine components of two sinusoidal functions that are not harmonically related and then evaluating the sine or cosine of the phase difference. Th e proposed techniques are shown to be very efficient in increasing the effe ctive table length and, hence, the frequency resolution of the oscillator. Further performance improvement can be achieved by using interpolation meth ods as demonstrated. Simulation results verify the analytical results and s how that the total harmonic distortion of the generated sinusoid is of the same order as that of the conventional digital LUT tunable sinusoidal oscil lator.