BROADBAND UNIDIRECTIONAL ULTRASOUND PROPAGATION

摘要

A passive, linear arrangement of a sonic crystal-based apparatus and method including a 1D sonic crystal, a nonlinear medium, and an acoustic low-pass filter, for permitting unidirectional broadband ultrasound propagation as a collimated beam for underwater, air or other fluid communication, are described. The signal to be transmitted is first used to modulate a high-frequency ultrasonic carrier wave which is directed into the sonic crystal side of the apparatus. The apparatus processes the modulated signal, whereby the original low-frequency signal exits the apparatus as a collimated beam on the side of the apparatus opposite the sonic crystal. The sonic crystal provides a bandpass acoustic filter through which the modulated high-frequency ultrasonic signal passes, and the nonlinear medium demodulates the modulated signal and recovers the low-frequency sound beam. The low-pass filter removes remaining high-frequency components, and contributes to the unidirectional property of the apparatus.

主权项

1. An apparatus for generating a collimated acoustic signal having a frequency fm or a band of frequencies centered at fm, from an input carrier signal having a frequency fc>fm amplitude modulated by fm, comprising:
a low-loss acoustic bandpass filter for receiving the modulated carrier signal, and having a bandwidth larger than an amplitude modulated sideband of the amplitude modulated fc; and an acoustic nonlinear medium for receiving and demodulating the amplitude modulated fc from said acoustic bandpass filter, whereby a collimated acoustic signal having a frequency fm is generated.