Patent ID: 9078062
Filing Date: 2015-07-07
Classification: H04R

Abstract:
1. An apparatus for generating a drive signal for a parametric loudspeaker, the apparatus comprising: a receiver for receiving an input audio signal; a pre-compensator for generating a pre-compensated envelope signal by applying a pre-compensation to the input audio signal, the pre-compensation at least partially compensating an envelope distortion of in-air demodulation of a modulated ultrasound signal; a first circuit for generating a complex base band signal, the first circuit being arranged to: generate a phase signal from the pre-compensated envelope signal in response to a predetermined function for determining a phase signal from an amplitude signal, the predetermined function generating a phase signal corresponding to a complex signal wherein a first frequency range of a first group consisting of a first range corresponding to positive frequencies and a second range corresponding to negative frequencies is suppressed relative to the other frequency range of the first group; and generate the complex base band signal with an amplitude corresponding to the pre-compensated envelope signal and a phase corresponding to the phase signal; a modulator for quadrature modulating the complex base band signal on an ultrasonic quadrature carrier to generate a modulated signal; and an output circuit for driving an ultrasound transducer from the modulated signal.