Long range wireless characterisation of 2.4 GHz SAW-based pressure sensor using network analyser

A 2.4 GHz range surface acoustic wave (SAW)-based pressure sensor was fabricated on a 41° YX LiNbO₃ substrate for a mechanical compression force measurement. For the first time, fabricated sensors were characterised wirelessly using the network analyser. Electron beam lithography was used for fine line patterning. Metal ground shielding was covered all over the cavity to reduce a coupling loss of the propagating SAW to the surrounding atmosphere. Equivalent circuit model and finite element methods were used to determine optimal design parameters. The three sharp peaks were obtained from three reflectors. As a mechanical force was applied to the piezoelectric diaphragm, the diaphragm was bended, resulting in the phase shifts of the reflected peaks. Obtained sensitivity was 2.9°/kPa.