| 摘要 |
1,268,225. Piezo-electric elements. THOMSON-CSF. 27 March, 1969 [3 April, 1968], No. 16233/69. Heading HIE. The thickness of a rectangular DT-cut quartz crystal plate is chosen to eliminate certain undesired modes of vibration. The fundamental resonance of such a plate is associated with a face shear vibratory mode, but undesired bending vibrations dependent upon the thickness of the plate may occur. For a plate of length L, width W and thickness E, the ratio A=W/L is chosen to obtain a high Q in a particular frequency range. Using the graph, a value of R=E/L (and hence a value of E) may be found which eliminates the unwanted bending modes. On the graph, the ordinates represent C=fL, where f is the resonant frequency in MHz and L is expressed in mm. The segments 2, 3, 4, 5, 11, 12 correspond to principle-mode resonances for A= 0.175 and A= 0À4, and the segments 6, 7, 8, 9, 13, 14 represent undesired modes. The angle of cut of the plate may be chosen to obtain zero frequency/temperature coefficient. Reference has been directed by the Comptroller to Specification 1,116,699. |
