Surface acoustic wave gyroscope

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A surface acoustic wave gyroscope using an operation frequency of 15 MHz, a wave mode of Rayleigh wave and a piezoelectric substrate of LiNbO3 128ﾟ Y-cut was designed. Electrodes of an interdigital transducer (IDT : called "generator IDT") and two reflectors are aligned for generating a standing wave on the surface. Two IDTs (called "sensor IDTs") and two reflectors for receiving a secondary wave are aligned perpendicularly into the electrodes which generate the primary standing wave. Perturbation electrodes are arranged between the IDTs. A principle of this gyroscope is receiving the secondary wave excited by the perturbation electrodes with rotation of the substrate. An output voltage of few tens of mV with rotation rate 2pi rad/s was estimated by using equivalent circuit models. This sensor with electrodes of aluminum and chromium and the size of 25mm x 45mm was fabricated by using photo-process.On sensor IDT,a different anti-resonance frequency from a resonance frequency of generator IDT and low Q factor was found from measuring admittance characteristic versus frequency. Therefor, output voltage will be decreased to less than one hundred muV.And waves scattered by the perturbation electrodes were observed. These scattered waves were detected by the sensor IDTs. Some perturbation electrode with different vibration condition from our design were found by vibration measuring. Further, the primary standing wave was not formed clearly. Thus, a vibrating table was used to detect the output of the gyroscope, for the output voltage was too low. The output of sensor IDT was amplified with locking in the frequency of table vibration. But, unfortunately, the output voltage could not detected yet.