Although there is increasing interest in the use of plane waves (PW) in high-frame-rate imaging, not much experimental data is available about their behavior in terms of nonlinear propagation. This paper presents a detailed study of fundamental and harmonic components of the ultrasound beam associated to PW transmission from a linear array. Simulations and hydrophone measurements of PW propagation in water were performed and compared to the results obtained for focused waves (FWs) at various levels of peak negative pressure (PNP). Experimental results confirm that, at comparable PNP, the amplitudes of the harmonics reached by PWs are always higher, over extended regions, than those achieved with FW. For example, at MI = 0.2 the PW second harmonic turns out to be 9 dB higher at 25 mm depth (i.e. in the focal region), and 20 dB higher at 40 mm depth. Simulations additionally show that when ultrasound waves propagate through blood or muscle, the situation is in general reversed but, at low MI, the second harmonic amplitude can still be higher in PW than in FW. Furthermore, it is shown that increasing the array aperture size yields higher harmonic growth in PW compared to FW.

尽管人们对在高帧率成像中使用平面波 (PW) 越来越感兴趣，但关于其非线性传播行为的实验数据并不多。本文详细研究了与线性阵列 PW 传输相关的超声波束的基波和谐波分量。对水中的 PW 传播进行了模拟和水听器测量，并与不同峰值负压 (PNP) 水平下的聚焦波 (FW) 获得的结果进行了比较。实验结果证实，在可比较的 PNP 下，在扩展区域内，PW 达到的谐波幅度始终高于 FW 达到的谐波幅度。例如，当 MI = 0.2 时，PW 二次谐波在 25 mm 深度（即聚焦区域）处高出 9 dB，在 40 mm 深度处高出 20 dB。模拟还表明，当超声波通过血液或肌肉传播时，情况通常相反，但在低 MI 下，PW 中的二次谐波幅度仍可能高于 FW 中的二次谐波幅度。此外，结果表明，与 FW 相比，增加阵列孔径尺寸会在 PW 中产生更高的谐波增长。