AN IMPROVED METHOD FOR DETERMINATION OF SURFACE-CHARGE DISTRIBUTION OF WEAK SPURIOUS MODES IN QUARTZ PLATES

The method described here accurately determines the two-dimensional su rface charge pattern of a weak mode existing in the vicinity of a stro ng mode in quartz crystal plate using an equivalent model that suitabl y approximates the surface charge frequency characteristics in the tar get modes measured at each measurement coordinate. The surface charge frequency characteristics are measured by an automated measurement sys tem based on the electrical probe method. The temperature characterist ics of the measured surface charge pattern of a weak mode near the fun damental thickness-shear mode in a rectangular AT-cut plate demonstrat ed that even for a weak mode, the present procedure provides patterns clearer than those obtained with a previous technique.