NOVEL PREPROCESSING TECHNIQUE TO IMPROVE HARMONIC DISTORTION IN AIRBORNE PARAMETRIC ARRAY

摘要

A novel modified preprocessing technique was proposed to reduce harmonic distortion in airborne parametric array, which was designed to reproduce highly directed audible sound. This technique was based on the idea that the harmonic distortion was not fully canceled around 10KHz because of the mismatch of phase and amplitude even though previous simple preprocessing was activated. In this paper, digital filter was designed to compensate for this phase and amplitude mismatch. This linearization technique has been verified by experiment of airborne parametric array of which carrier frequency was 40KHz. The results shows that second harmonic was reduced 11dB and total harmonic distortion (THD) was improved 20% around 10KHz compare to previous preprocessing. Proposed modified preprocessing is effective and good results render this technique suitable for a reproduction of high quality audible sound with high directivity.