Patent ID: 8240911

Claim:
A wireless passive temperature sensor, comprising: a surface acoustic wave delay line comprising, a piezoelectric substrate having a thermal coefficient of frequency, a launch interdigital transducer, disposed on the surface of the piezoelectric substrate and adapted to launch a surface acoustic wave at a resonance frequency in the piezoelectric substrate when a RF electric field is applied across the launch interdigital transducer, and a reflection interdigital transducer, disposed in the acoustic path of and spaced a delay length from the launch interdigital transducer on the piezoelectric substrate and adapted to at least partially reflect the launched surface acoustic wave back to the launch interdigital transducer; and an antenna adapted to receive a transmitted RF pulse and apply the RF electric field across the launch interdigital transducer to launch the surface acoustic wave, and to retransmit an RF pulse from the reflected surface acoustic wave received by the launch interdigital transducer; and wherein the delay time between the launched surface acoustic wave and the received reflected surface acoustic wave at the launch interdigital transducer is dependent on the thermal coefficient of frequency of the piezoelectric substrate.