Low-Distortion Sine Wave Generation Using a Novel Harmonic Cancellation Technique

Abstract

A novel technique is proposed to generate robust, low distortion sine waves. In this method, outputs of a phase shift oscillator (PSO) are weighted and summed to obtain multiple outputs with very low distortion and precise phase relationship. The method allows a programmable number of harmonic distortion components to be cancelled over a wide frequency range. This work derives the condition for the weights on the outputs of the PSO to be a real quantity, and demonstrates how this can be used to generate low distortion sine waves. With the proposed method, in an N-stage PSO, harmonics up to N-2th can be canceled. Simulation results using commercial operational amplifier spice models are presented to demonstrate low distortion sine wave generation over 2 kHz-180 kHz frequency range. The method has been experimentally verified using extremely low-cost, discrete components to produce 100 dB total harmonic distortion (THD) sine wave.