There is known a surface acoustic wave sensor for measuring properties or ingredients of a liquid which is an analyte, by means of a surface acoustic wave device.
The surface acoustic wave sensor, which is constructed of a piezoelectric substrate on which is mounted a detecting section which reacts with a component contained in an analyte sample, detects properties or ingredients of a liquid which is an analyte by measuring electric signals responsive to variations in surface acoustic wave (SAW) propagating through the detecting section (for example, refer to Patent Literature 1).
The SAW sensor disclosed in Patent Literature 1 measures the concentration of an analyte by detecting a phase difference in SAW. A quadrature modulation system is customarily adopted for phase difference measurement from the standpoint of an extended measurable phase range (for example, refer to Non Patent Literature 1).