高阶模式兰姆波色散特性测量研究

Study on Measurement of Dispersive Characteristics of Higher Order Mode Lamb Waves

由于设计超高频兰姆波微传感器的需要,该文测量并分析了通过叉指换能器激发高阶模式兰姆波的传播特性。在建立测量系统的基础上,通过时域频域转换法获得了高阶模式兰姆波的色散特性。该系统可自动测量兰姆波的幅频响应与相频响应。再通过反傅里叶变换,获得器件的脉冲响应特性。进而在频域中区分不同模式,并通过傅里叶变换获得兰姆波色散曲线。由于高阶模式兰姆波的相速度远大于表面波的速度,因此基于此设计的振荡器频率更高,传感器更灵敏。

The dispersive characteristics of higher order mode Lamb waves（HOMLW） excited by inter-digital transducers（IDT） were measured and analyzed, which were necessary for designing micro-sensor in ultrahigh fre- quency（VHF）. A measurement system was set up,in which dispersive characteristics of HOMLW were obtained by the method of transform between frequency and time domains. The characteristics of amplitude-frequency and phase- frequency of Lamb wave were auto-measured by the system. By IFFT, the pulse response of the IDT device was ob- tained. Different modes were separated in time domain and dispersive curve of each mode was calculated by FFT. The phase velocity of HOMLW is greater than the surface wave（SAW） velocity and an oscillator in higher frequency could be made, so the absolute sensitivity of micro-sensor could be increased.