Title :
Third-order parametric array generated by distantly spaced primary ultrasonic tones
Author :
Garner, Glenwood ; Steer, Michael B.
Author_Institution :
Dept. of Electr. & Comput. Eng., North Carolina State Univ., Raleigh, NC, USA
fDate :
4/1/2012 12:00:00 AM
Abstract :
Traditional parametric arrays are produced by a second-order nonlinear interaction between two primary ultrasonic tones that are close in frequency, resulting in a difference tone that is in the audio band. This article presents a parametric array produced by a third-order nonlinear interaction between two primary ultrasonic tones that are distantly spaced in frequency such that one tone is approximately the second harmonic of the other. The result is a third-order lower intermodulation (IM3) tone in the audio band with greater directivity and lower side lobe amplitude than comparable second-order fields. Measurements are presented that compare the directivity of 1-, 2-, and 4-kHz difference tones to that of 1-, 2-, and 4-kHz IM3 lower tones. Furthermore, a cascaded second-order approach for N-element transducer arrays is used to model third-order scattering with good agreement between measurement and theory.
Keywords :
acoustic variables measurement; harmonic generation; intermodulation; ultrasonic scattering; ultrasonic transducer arrays; N-element transducer arrays; audio band; cascaded second-order approach; difference tone directivity; distantly spaced primary ultrasonic tones; frequency 1 kHz; frequency 2 kHz; frequency 4 kHz; lower side lobe amplitude; second harmonics; second-order fields; second-order nonlinear interaction; third-order lower intermodulation; third-order nonlinear interaction; third-order parametric array generation; third-order scattering; Acoustics; Arrays; Attenuation; Electric shock; Harmonic analysis; Scattering; Transducers;
Journal_Title :
Ultrasonics, Ferroelectrics, and Frequency Control, IEEE Transactions on
DOI :
10.1109/TUFFC.2012.2255