Ultrasonic parametric amplifier.

摘要

An ultrasonic parametric amplifier incorporates a duct (4) having rigid cylindrical wall with a periodic inner surface that undulates sinusoidally in an axial direction, and an element (16) for heating the external surface of the wall. The sinusoidal undulations of the periodic inner surface have a wavelength which is about half of the wavelength of the waves of ultrasonic energy propagating through a fluid filling the duct. The waves are amplified by synergistic interactions of the ultrasonic waves with the periodic duct walls when heat is added in a predetermined manner, thereby compensating for the exponential decrease in fluid temperature which would otherwise lead to detuning of the amplifier. <IMAGE>