Nonlinear ultrasound fields simulation of harmonics from exponential and bessel beams sources

Abstract

It's well known that the harmonic imaging quality can be improved by using sources that radiate narrower and attenuated sidelobe beams. Hence we try to enhance the harmonics' cartography by studying different source's power distributions. We developed a numerical code, using the spectral method, in order to resolve the parabolic wave equation. The numerical results are compared to those given by other researchers in order to validate our algorithm. Two source's power distributions (exponential and Bessel beams) are studied and compared to the uniform case. The use of exponential source leads to harmonics diagrams without sidelobes neither nearfield oscillations. But the beam width is increasing with propagation. The Bessel source presents a limited diffraction beam. The beam width is almost constant throughout the nearfield and the transition zone. The sidelobes have a weak level in the fundamental curves and they don't appear in the second harmonic ones.