Impedance loaded SAW sensors offer a wide range of measurement opportunities

Surface-acoustic-wave interdigital tags can be employed as passive transponders for conventional sensors of capacitive, inductive, and resistive types. An interdigital transducer is used as a loadable reflector, while other fixed reflectors are used as reference bits. The load of the programmable reflector influences both the phase and amplitude of the reflected wave. The principle is discussed, and applications for the measurement of light, pressure, and temperature are presented in this paper.