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众所周知,在晶体文献中,不平行的晶片表面将引起AT切谐振器性能的恶化。这种恶化是由于谐振器所要求的工作模的动态电容的减小所致,通常并不引起所观察的寄生模动态电容的相应减小。在假设晶片两边的厚度有微小线性变化(楔形)的情况下,已经研究出一种重电极矩形AT切晶片的厚度切变振动模式。这种模式预示出相应于各种非谐振动泛音模式的驻波将“聚集”在晶片的较厚区域。高次非谐模将比低次非谐模受到楔形的影响要小。这种性能的明显结果是最低次模的动态电容(所要求的工作模)将会减小,而高次模(寄生模)的动态电容可能一点也不减小。
It is well known that in the crystal literature, non-parallel wafer surfaces will cause deterioration of AT cut resonator performance. This deterioration is due to the reduction of the dynamic capacitance of the working mode required by the resonator, which usually does not cause a corresponding reduction in the observed dynamic capacitance of the parasitic mode. In the case of a slight linear variation in the thickness of both sides of the wafer (wedge shape), a thickness-shear vibration mode of a heavy electrode rectangular AT cut wafer has been investigated. This mode predicts that standing waves corresponding to various modes of harmonic non-harmonic vibrations will “gather” into thicker regions of the wafer. Higher-order anharmonic modes are less affected by wedges than lower-order anharmonic modes. The obvious result of this performance is that the lowest-order dynamic capacitance (the required working mode) will decrease, whereas the dynamic mode of the higher-order mode (parasitic mode) may not decrease at all.