| Abstract: | The integration of surface acoustic wave (SAW) filters, microfabricated
transmission lines, and sensors onto polymer substrates in order to
enable a passive wireless sensor platform is described herein. Incident
microwave pulses on an integrated antenna are converted to an acoustic
wave via a SAW filter and transmitted to an impedance based sensor, which
for this work is a photodiode. Changes in the sensor state induce a
corresponding change in the impedance of the sensor resulting in a
reflectance profile. Data collected at a calibrated receiver is used to
infer the state of the sensor. Based on this principal, light levels were
passively and wirelessly demonstrated to be sensed at distances of up to
about 12 feet. |