US Patent 11003971 Ultra-wide-band saw sensor with hyperbolically frequency-modulated etched reflector

There is disclosed a surface acoustic wave sensor. An interdigital transducer (IDT) and a first reflector are formed on a surface of a piezoelectric substrate. The first reflector is displaced from the IDT in a direction of acoustic wave propagation. The first reflector includes a plurality of elongate reflective elements including a first reflective element and N additional reflective elements, where N is a positive integer. A long axis of each of the reflective elements is perpendicular to the direction of acoustic wave propagation, and a distance between adjacent reflective elements along the direction of acoustic wave propagation is a linear function of distance from the first reflective element along the direction of acoustic wave propagation.