基于时间反转法的相控换能器声场的仿真研究

The simulation study of acoustic pressure field about HIFU phased array transducer based on time reversal method

相控换能器具有焦距可调的优势。本文以82阵元相控换能器建立的3D数值仿真模型为例,基于时间反转法提取阵元的激励信号,利用时域有限差分(FDTD)法对Westervelt声波非线性传播方程进行声场数值仿真,研究不同阵元分布、焦点偏离声轴的距离、设定焦距大小对形成声场的影响,可调控范围及其消除旁瓣方法。研究结果表明,随机分布相控阵可明显降低声场中的旁瓣;随着偏离声轴距离的增加,主瓣声压幅值逐渐减小,旁瓣与主瓣的最大声强比值r逐渐增大,且沿声轴的可调控范围逐渐减小;随声轴方向上设定焦距的增加,主瓣声压幅值先增大后减小,r值先减小后增大;基于时间反转法的高声压旁瓣消除法可在一定程度上扩大相控阵声场的可调控范围。

Phased array transducer has the advantage of adjustable focal length. In this paper, the incentive signal of each element is abstracted by time reversal method and the acoustic pressure numerical simulation is undergone through finite difference time domain （FDTD） of Westervelt acoustic nonlinear transmission formula based on the 3D numerical simulation model of 82-element phased array transducer. The effect of different element distribution, the distance off the acoustic axis and the setting focal length on the forming acoustic pressure field is discussed. The adjustable range of acoustic pressure field and the method which eliminate sidelobe is also analyzed. The results show that the phased array transducer with quasi-random distribution can suppress the sidelobe significantly. As the distance off the acoustic axis increasing, the acoustic pressure amplitude of the main lobe decreases, the acoustic intensity ratio between the maximum sidelobe and the main lobe （r value） increases, and the adjustable range along the acoustic axis decreases. The acoustic pressure amplitude of the main lobe increases firstly and then decreases, while r value decreases firstly and then increases with the increase of setting focal length along the acoustic axis. To some extent, the acoustic adjustable range can be extended by the high acoustic pressure sidelobe elimination method based on time reversal method.