Improving the insertion loss and sensitivity over existing SAW strain sensor

In this paper, we clarify the relationship between strain and SAW. A SAW can be excited on a piezoelectric substrate using an IDT and its propagation characteristics are easily affected by external physical, such as stretching and bending. External force applied to PCB substrate bonded to a piezoelectric substrate induces strain at the substrate surface, which causes changes in the elastic constant and density of the substrate and hence the propagation velocity of the SAW. A strain sensor can be constructed based on detection of the SH wave mode. In strain measurement, the propagation velocity of the SAW was found to vary in linear proportion to the strain applied to the propagation path. When compared with other SAW based strain sensor, this sensor has about 30% higher sensitivity. This sensor was demonstrated experimentally to be very effective for strain.