MEASUREMENT OF THE RELATIVE CHANGE OF SAW VELOCITY BY INTERFERENCE METHOD

A phase interference method, for measurement of the relative change of surface acoustic wave velocities, is presented. In this method we only measure the frequencies and relative length ratio instead of the absolute value of SAW velocities and the propagation distance. It is superior to the conventional pulse technique and phase comparison method in the simplicity of measuring equipments and the easiness of measurement. We have got the relative change of SAW velocities on the metallized surface of 127.86° YX-LiNbO₃, ΔV/V_∞=0.02866. with relative error within 0.25%.
The method can also be used to measure the absolute volue of SAW velocity accurately if the length of propagation is measured accurately.
The test data of ΔV/V_∞ and V_∞ for several orientation of LiNbO₃ and quartz and the error analysis are given.