Spread Spectrum Techniques for Wirelessly Interrogable Passive SAW Sensors

Recently surface acoustic wave (SAW) sensors for temperature, pressure, strain, etc. were investigated and tested. They use the change in SAW time delay due to the quantity to be measured. Increasing interest was initiated by the possibility of wireless readout. It is shown here, that the well known spread spectrum techniques (chirp impulse compression, CDMA, etc.) allows an increase of both, sensitivity and accuracy of measurement and a discrimination of several sensors simultaneously interrogated. Some applications (temperature measurement with mK resolution, coded sensors) are demonstrated. We show some mathematical simulations and preliminary experimental results.