Saw Gyroscopic Effect

SAW (Surface Acoustic Wave) is a kind of acoustic wave whose energy concentrates on the surface of the transmission trace, having been found by British physician Rayleigh in the course of seism research. Along with more research on the SAW, especially after the invention of IDT (Interdigital Transducer) by R. M. White and F. M. Voltmov, the research and application of SAW are accelerated sharply. In many domains, such as radar communication and signal processing, SAW plays an important role.In the course of the SAW propagation, the changes of the physical parameters or the chemical parameters outside can induce the changes of the property of SAW propagation trace, which can induce the changes of the velocity of SAW or the dimension of the substrate. The frequency drift induced by the changes of the velocity of SAW or the dimension of the substrate can be detected to sense the parameters outside. According to this principle, some sensors sensing various physical parameters and chemical parameters (such as temperature, pressure, magnetic field, electric field and gas/fluid phase etc..) can be designed and fabricated. In terms of the sensor development trend of numeralization, integration and high degree of accuracy, since 1980's there is much improvement about the SAW sensor in Occident and Japan, and SAW temperature and gas phase sensor with high degree of accuracy are in utility.But there are some difficulties in the application of inertia sensor. According to the present literature, the gyroscope effect of SAW has been proven existing on the rotating substrate theoretically. Under the interference of Coliorios force and centrifugal force, there exists a approximate linear relation between the velocity of the SAW and the angle rate. Meanwhile the change of the velocity of the SAW can be denoted by the frequency drift. The existence of SAW gyro effect being proven by experiments has not been reported yet.Based on the Christoffel's equation including Coriolis force, a numeric simulation program using MATLAB has been got. The simulation result indicates that velocity of two bunches of SAW along reverse directions interfered by Coriolis force will change in a reverse trend. According to this result, a difference structure is designed to produce two bunches of SAW with reverse directions. Theoretically, this structure can decrease the influence of the temperature drift of SAW oscillator, and double the sensitivity. In terms of this structure, an actual part is fabricated with LiNbO₃ as substrate. Meanwhile, the whole oscillation circuit and the frequency mixing circuit are designed to processing the two channels of signal. Using a high speed spinner, a set of experimental data approaching the theoretic data has been achieved.