中文摘要：

超声相控换能器具有焦距可调,多焦点聚焦的特性。以64阵元球面相控换能器为例,利用Westervelt声波非线性传播方程及时间反转法（TR）对64阵元圆形相控换能器在水中不同焦点处形成的焦域声压分布进行时域有限差分法（FDTD）仿真研究。研究结果表明,频率为0.5-0.8 MHz时自聚焦形成的焦距均小于球面几何焦距;单焦点聚焦时,随着焦点偏离声轴的距离增大,焦点处的最大声压逐渐降低,随着焦距增大,旁瓣与主瓣最大声强比值先减小后增大;频率为0.7MHz,双焦点聚焦时,在焦点间设定距离〉7mm的条件下,焦点间旁瓣很小,当焦点间距离≤2.5mm时,两焦域融合成单一焦域。

英文摘要：

Phased array has the characteristics of steering focus and forming multiple loci. In this study, the Westervelt nonlinear acoustic propagation equation and the time reversal theory （TR） are used to calculate the pressure distribution of different focal regions in water which is based on a 64-element phased array by the finite difference time domain （FDTD） method. Simulation results demonstrate that the focal lengths formed by self-focusing are less than the spherical geometry at 0.5-0.8 MHz. When forming single focus, the maximum pressures of foci decrease as the distance of off-axis increasing. The ratio of intensity between side lobe and main lobe firstly decreases and then increases. When forming two foci at 0.7 MHz, the intensity of side lobe is low as the distance between two foci gets greater than 7 mm, and two loci fuse as the distance is less than or equal to 2.5 mm.