Patent ID: 7929715
Filing Date: 2011-04-19
Classification: H04R

Abstract:
1. An ultra directional speaker system comprising: a first envelop calculator which calculates an envelop of an audio input signal currently being inputted; a square root operator which calculates a square root of a first envelop signal calculated by the first envelop calculator to generate a square root signal of the first envelop signal; a pre-distortion adaptive filter which applies an adaptive filter coefficient update term according to an adaptive filter coefficient determined in a previous stage to the audio input signal currently being inputted to carry out a distortion compensation and generate a compensated signal; a second envelop calculator which calculates an envelop the compensated signal to generate a second envelop signal; an error calculator which compares the second envelop signal and the square root signal of the first envelop signal to generate an error signal; an adaptive filter coefficient updater which calculates the adaptive filter coefficient update term and the adaptive filter coefficient from the error signal; a dynamic vestigial sideband modulator which dynamically modulates the compensated signal to an ultrasonic band to generate a modulation signal; an ultrasonic converter model which models an inverse filter corresponding to a frequency characteristic of an ultrasonic converter and applies the inverse filter to the modulation signal to generate a filtering signal; an ultrasonic amplifier which amplifies the filtering signal; and the ultrasonic converter which converts the amplified filtering signal to an ultrasonic signal.