平面超薄准直器件的参数依赖性

本文设计了一具有高效强指向性的平面超薄人工结构,当平面声波垂直入射到该结构时,若中心狭缝处产生的F-P(Fabry-Perot)共振和两侧类亥姆霍兹凹槽的共振频率耦合时,会产生一具有高度指向性的准直声束。通过对结构两侧的凹槽阵列的作用、凹槽周期D和凹槽数量r的探讨,发现凹槽阵列可将散射声波转换成声表面波,大大提高了透射效率,同时结构的共振频率、声透射率和准直效果和D、r的变化关系不大,说明对该结构准直效应产生影响的是F-P共振频率和类亥姆霍兹共振器共振频率,与布拉格散射无关。这一发现有助于在降低结构尺寸的同时仍保持结构的有效性,为后续指向性器件的应用提供了理论依据。

Parameter dependence of thin planar collimating device

A high-efficiency collimation of acoustic waves through an ultra-thin planar structure is designed in this paper. When incident plane waves propagate into the structure vertically, a high collimated acoustic beam is generated as the Fabry-Perot (F-P) resonance in the aperture is coupled with the bilateral Helmholtz-like resonators. We investigate the design principle of the Helmholtz-like grooves, as well as the dependence of transmission efficiency and far-field directivity on the period of the Helmholtz-like array, D, and the number of the grooves, r. The results show that the grooves convert the scattered waves into the acoustic surface waves to improve the transmission efficiency greatly. And the change of D and r has not much influence on the resonant frequency, transmission coefficient and directivity significantly, so that the collimation functionality is related to the coupling between F-P and Helmholtz-like resonances instead of Bragg scattering. This may contribute to downscale the collimation device without decreasing the efficiency of the structure, which provides theoretical basis for further application of collimating devices.