Composite substrates for saw tags or RFID and sensors applications

A physical quantity-determining device comprising two or more surface acoustic wave tag devices, at least one of the two or more surface acoustic wave tag devices comprising:

• an acoustic wave propagating substrate comprising a composite substrate including a base substrate and a piezoelectric layer;
• at least one transducer structure comprising inter-digitated comb electrodes disposed over the acoustic wave propagating substrate;
• and
• a set of reflectors positioned at various delays on one side of the transducer structure in the direction of propagation of an acoustic wave having a wavelength, each reflector comprising a different number of metallic strips, and wherein the metallic strips of each reflector are connected to each other and shorted;
• wherein a crystallographic orientation of the piezoelectric layer with respect to the base substrate is such that the propagation of a shear wave inside the piezoelectric layer and in the direction of propagation corresponding to the acoustic wave is enabled;
• and
• wherein a thickness of the piezoelectric layer is smaller than the wavelength.