| Through theoretical calculations using the extended Christoffel-Bechmann method and experiments, three operation modes of the LFE devices, which were referred to as the pure LFE, quasi-LFE and pseudo-LFE modes, were presented. Several about 5 MHz LFE devices with similar geometry using the (yxl)-58¡ã LiNbO3, (yxl)-16.5¡ã LiTaO3 and AT-cut quartz crystals were fabricated for analyzing three LFE operation modes. Their piezoelectric coupling factors and acoustic wave phase velocity for LFE and TFE were calculated for designing LFE devices. The motional resistance at resonance was theoretically derived from the device geometry and material constants and was well corresponding to the measured results for analyzing three modes. |