Impedance loaded SAW sensors offer a wide range of measurement opportunities

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