A wireless AQP pressure sensor using chirped SAW delay lines structures

We report of the design of a SAW delay line developed for a wireless pressure sensing system operating in the 434 MHz ISM-band. The structure is a one port configuration fabricated on quartz 37.5/spl deg/rotYX. It is hermetically sealed in all-quartz-package (APQ) technology with the SAW structure being placed on a diaphragm inside the cavity. The sensor allows for the measurement of absolute pressure values in the range from 0 to 8.5 bar. The SAW structure shows a linear phase although it incorporates chirped SAW components for enhancing the sensor sensitivity. The SAW structure is built up of two overlap-weighted dispersive split finger interdigital transducers (IDTs). An improvement of the sensor sensitivity by a factor of 32 compared to systems using non-dispersive SAW components has been achieved.