Design, simulation and testing of planar spiral coils for the time-gated interrogation of quartz resonator sensors

A technique for contactless electromagnetic interrogation of quartz resonator sensors is proposed and validated. The technique is based on the separation in time of the excitation and detection phases, exploiting the sensing of the transient response of the resonator. Contactless operation is achieved by means of electromagnetic coupling between spiral planar coils connected to the interrogation circuit and the sensor. The typical operating frequencies of quartz resonators in the megahertz range limit the working range to short distances. Analytical modeling and numerical and finite element simulation of the geometry of the coils have allowed to extend working operating distances up to 10 cm.