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对二维声表面波压电声子晶体在射频段的带隙特性,进行了时域有限差分法(FDTD)理论推导和计算,并提出实验方法对比验证。FDTD计算模型考虑了压电效应,引入周期边界条件以节省计算空间和时间,采用完全匹配层以解决声表面波在截断边界处的虚拟反射问题。实验上分别设计有/无二维压电声子晶体的两种宽频带延迟线结构,测量两种延迟线的传输系数取差值,得到了二维压电声子晶体的带隙;其中通过时域加窗函数保留一次传输信号,进行干扰信号的去除。以铝/128°YX-LiNbO3二维压电声子晶体为例,该FDTD方法、商业有限元软件COMSOL、实验方法均得到了100~500 MHz射频段内的多个带隙,三种带隙对比证明了FDTD计算带隙与实验测量带隙一致,比COMSOL计算的计算带隙精度更高。
The time-domain finite difference method (FDTD) theory is derived and calculated for the bandgap characteristics of two-dimensional SAW piezoelectric phonon crystals in the radio frequency band. The experimental verification is given. The FDTD calculation model considers the piezoelectric effect, introduces periodic boundary conditions to save computational space and time, and employs perfect matching layers to solve the problem of surface acoustic reflection at the cutoff boundary. Experimentally design two kinds of wide-band delay line structures with / without two-dimensional piezoelectric phononic crystals, respectively, and measure the difference between the transmission coefficients of the two kinds of delay lines to get the bandgap of two-dimensional piezoelectric phononic crystals. Time-domain windowing function to retain a transmission signal, the interference signal removal. Taking the aluminum / 128 ° YX-LiNbO3 two-dimensional piezoelectric phonon crystal as an example, the FDTD method, the commercial finite element software COMSOL, and the experimental method all obtained multiple band gaps in the 100-500 MHz radio frequency band, The comparison between FDTD calculated band gap and experimentally measured band gap is more accurate than that calculated by COMSOL.