平面超薄准直器件的参数依赖性

Parameter dependence of thin planar collimating device

该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Fabry-Perot(F-P)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与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。

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.