High resolution and low distortion digital look-up-table sinusoidal oscillators

We propose two new methods to reduce the spurious harmonic distortion of a digital sinusoidal signal generated using the look-up-table (LUT) method. S purious harmonic distortion arises when we try to interpolate the value of a sample that is not present in the LUT. The first proposed method depends on a real time evaluation of the missing sample value without the need for any additional LUT length. The second proposed method requires an additiona l table and some real time processing to calculate the value of the interpo lated sample. The two proposed methods are simulated and their performance is compared with that of the existing methods; namely direct LUT, linear in terpolation and trigonometric interpolation. The simulation results show th at our proposed methods are superior to both direct LUT and linear interpol ation methods. Moreover, for practical table lengths, the performance of ou r proposed methods is of the same order as that of the trigonometric interp olation method.