Patent ID: 7663290

Claim:
A sensor comprising: a substrate; a medium deposited on the substrate and on which a surface acoustic wave propagates; a reference electrode deposited on the substrate, that serves as a reference surface of potential; an antenna that receives and transmits a signal; a transducer deposited on the medium, that comprises a first electrode connected to the antenna and a second electrode connected to the reference electrode and arranged opposite to the first electrode, and that has a function of converting a signal received by the antenna into a surface acoustic wave propagating on the medium, and a function of converting a surface acoustic wave propagating on the medium and reaching the transducer into a signal and outputting the signal to the antenna; a reflector that throws back a surface acoustic wave generated by the transducer, propagating on the medium, and reaching the reflector, toward the transducer; and an impedance converter connected to the reference electrode, impedance of which changes in response to a change in circumstances surrounding the sensor.