Surface acoustic wave devices having frequency response that can be adjusted

摘要

In the manufacture of surface acoustic wave devices it is necessary to manufacture master patterns from which interdigitated electrodes are produced photographically. The manufacture of the master is expensive and a new master is needed for each new device required to operate at a different frequency. The invention overcomes this problem in the device shown in FIG. 1 by the use of transducers 2 and 5, each constituted by separate groups 3 or 6 of interdigitated fingers. The effect of this is for the transducer to have peak frequency responses at a whole series of frequency values. These frequency values can be shifted up or down by varying the velocity of the surface acoustic waves in the region of the appropriate transducer. This is done using any one of a number of different methods but, in the embodiment of FIG. 1, metal layers 8 and 9 are applied and then adjusted in size until a peak of the transducer 2 coincides, at the desired frequency, with a peak of the transducer 5. PPIn this way two masters for producing electrodes in the patterns shown as 2 and 5 in FIG. 1 can be used in the manufacture of surface acoustic wave devices having a whole range of different frequency responses.