时变参数调制介质声学逆反射特性
Acoustic retroreflection characteristics of time-varying parameter modulated medium
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摘要: 提出了一种利用时变参数调制介质实现声学逆反射效应的方法。建立了垂直入射和斜入射下平面波在时变参数调制介质上的声反射理论模型, 得到了声压复反射系数的解析表达式, 揭示了声学逆反射效应的三波非线性耦合机理。利用时域有限差分法仿真研究了时变参数调制介质的厚度、调制深度、调制频率对声学逆反射传播的影响, 仿真结果与理论分析吻合较好。结果表明, 调制频率为入射平面波频率二倍时, 时变参数调制介质可产生幅度可调的逆反射波; 逆反射波的幅度会随着介质厚度、声速调制深度的增大而增强。所提声学逆反射器具有通道数多、结构简单、可调性好的优点。Abstract: A method of realizing acoustic retroreflection using time-varying parameter modulated medium is proposed. An acoustic propagation model for acoustic reflection of plane waves under both vertical and oblique incidence on time-varying parameter-modulated media is established, and analytical expressions for the complex pressure reflection coefficients are derived. This revealed the three-wave nonlinear coupling mechanism underlying the acoustic retroreflection effect. Numerical simulations are conducted using the finite-difference time-domain method to investigate the influence of the thickness, modulation depth, and modulation frequency of the medium on the propagation of the retroreflected wave. The simulation results align well with the theoretical predictions. An obvious retroreflection phenomenon occurs when the frequency of the sound speed modulation is twice that of the incident sound wave. There is obvious retroreflection phenomenon under the condition that the sound speed modulated frequency is twice the frequency of the incident sound wave. The proposed acoustic retroreflector has the characteristics of more channels, a simple structure and good tunability.