| 摘要 |
A surface-wave filter has a wave-propagating medium of ferroelectric material that exhibits a rate of change of surface-wave velocity which increases with increasing degree of poling more rapidly than its surface-wave coupling factor increases as the poling level is raised. The ultimate transducer interaction efficiency is a function of the coupling factor. Moreover, the material is poled in an amount that effects a desired surface-wave velocity while, at the same time, producing a surface-wave coupling factor that is significantly less than that corresponding to an optimum value with respect to transducer interaction efficiency. Completing the structure, an input transducer serves to launch acoustic surface waves and an output transducer responds to those waves by developing an output signal.
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