Surface acoustic wave probing with spaced interdigital transducers

We have found that interdigital surface acoustic wave (SAW) transducers deposited on glass substrates and positioned very close to a piezoelectric crystal delay line surface (’’spaced transducers’’) may be used to simulate identical transducers fabricated directly on the surface, for pretesting and prealignment of SAW devices. A novel spaced transducer mounting technique has been developed that utilizes a free floating gimbal, which permits positioning the spaced transducer substrate next to the delicately polished SAW substrate without any mutual wiping. This feature greatly extends the reliability of the spaced transducer and overcomes the problem of damaging the surface polish. The gimbal mechanism is mounted on a mobile support which ensures good positioning and orientation accuracy. A number of important uses for the new spaced transducer configuration in connection with surface acoustic wave delay line simulation are described, and a brief treatment of the electrical and coupling properties of spaced transducers is also presented.