Centre for Telecommunication Studies, Pontifical Catholic University of Rio de Janeiro, Rio de Janeiro, Brazil.
School of Energy and Electronic Engineering, University of Portsmouth, Portsmouth, PO1 3DJ, UK.
Ultrasonics. 2022 Aug;124:106772. doi: 10.1016/j.ultras.2022.106772. Epub 2022 May 25.
Array transducers can allow wavelength and frequency selectivity and can be used to generate different types of waves, such as ultrasonic bulk or guided waves. Dual-array transducers consist of two interlaced arrays, where the elements of each array are electrically connected. Therefore, by driving each array with a pair of phased pulses one can achieve a degree of wave generation control that allows unidirectional generation, unlike single array transducers that generate waves in both 0° and 180° directions with respect to the array's longitudinal axis. In this paper, we present a one-dimensional analytical model to determine the ultrasonic waves generated by dual-array transducers based on the excitability of the array in the frequency-wavenumber domain, the so-called operation region, determined by the joint spatial and temporal spectrum of the dual-array. We further exploited it to analyse the effectiveness of unidirectional generation with time-delayed excitation signals that provide ideal constructive or destructive interferences. The model also provides the time-domain received waveforms, which were compared to experimentally generated shear-horizontal ultrasonic guided waves, with a dual periodic permanent magnet array electromagnetic acoustic transducer, showing very good agreement. The adequate selection of the excitation signal allowed one to obtain up to about 40 dB unidirectionality experimentally.
数组换能器可以实现波长和频率选择性，并可用于产生不同类型的波，如超声波体波或导波。双数组换能器由两个交错的数组组成，其中每个数组的元件都电连接。因此，通过用一对相移脉冲驱动每个数组，可以实现一定程度的波产生控制，从而实现单向产生，而不像单数组换能器那样，相对于数组的纵轴，在 0°和 180°方向上产生波。在本文中，我们提出了一种一维分析模型，基于数组在频波数域中的可激性，即所谓的操作区域，来确定双数组换能器产生的超声波。该操作区域由双数组的时空联合频谱确定。我们进一步利用它来分析具有时移激励信号的单向产生的有效性，这些信号提供了理想的建设性或破坏性干扰。该模型还提供了时域接收波形，与实验产生的剪切水平超声导波进行了比较，使用的是双周期性永磁体阵列电磁声换能器，结果非常吻合。通过适当选择激励信号，实验中可以获得高达约 40 dB 的单向性。
