The distortion analysis of the Single Side Band method for parametric loudspeaker based on orthogonal envelope detection

According to the Hilbert transform properties, the self-demodulated signal’s distortion of the Single Side Band (SSB) method for parametric loudspeaker is analyzed theoretically by employing the orthogonal envelope detection method. It is proved that there is no distortion in the self-demodulated signal of the single side band method when a single-frequency signal is inputted, but the distortion is quite high when a wide-band signal is inputted, by which the incorrect concept existing for a long time that there is no distortion existing in the self-demodulated signal of the single side band method is rectified. Furthermore, a squared envelope distortionless condition for the signal processing methods of parametric loudspeaker is presented to provide an effective criterion for their development. A method to reduce the inter-modulation distortion of the single side band method for parametric loudspeaker by introducing a modulation factor is proposed, and it is also claimed that the method will result in a lower output power of the self-demodulated signal.