ACOUSTIC OSCILLATOR WITH ELECTRONIC FEED-BACK INCLUDING NON-LINEAR CONTROL

摘要

An acoustic oscillator arrangement includes an acoustic system having at least one acoustic transmission path through it, and at least one mode. The acoustic transmission path is of variable length. A controller is provided with an amplifier and a feedback network which together provide a positive feedback oscillator for exciting a mode of the acoustic system. The feedback network comprises a non linear amplitude control element (N-LACE), a frequency dependent gain element with an electronic transfer function, and a phase compensator. The acoustic oscillator arrangement also includes an acoustic transmitter which launches an acoustic signal into the acoustic system based upon an output from the controller, and an acoustic receiver which receives an acoustic signal from the acoustic system which is fed back to the controller. Such a stabilized positive feedback arrangement is self exciting at the effective resonance frequency of the acoustic system and avoids the need for an external fixed or variable frequency driver.