Extremely High Frequency Resolution and Low Harmonic Distortion Digital Look-Up-Table Sinusoidal Oscillators

New techniques to efficiently increase the frequency resolution of digital sinusoidaloscillators based on look-up-table (LUT) methods are proposed. The increase in frequencyresolution is achieved while maintaining very low level of spurious harmonicdistortion. The proposed techniques increase the LUT length to a level at which thespurious harmonic distortion is negligible. The first proposed technique is based onpartitioning the address register into three sets and dividing the available LUT lengthinto three smaller tables addressed according to the content of the address register sets.The second proposed technique utilizes one LUT and interpolates the values of thesamples that are not stored in the table. The third proposed technique is similar to thefirst technique with the advantage of simpler implementation and lower levels ofspurious harmonic distortion. The proposed techniques are simulated and their performanceis compared with that of the direct LUT and trigonometric interpolationmethods. The simulation results show that the proposed techniques are superior to bothdirect LUT and trigonometric interpolation methods