Wireless interrogation techniques for sensors utilizing inductively coupled resonance circuits

The methods needed to interrogate passive resonance sensors are studied. A portable impedance measurement unit and the methods to extract a coupling coefficient compensated resonance frequency are presented. The interrogation methods are demonstrated with ECG and pressure measurements. The results show that the quality of the ECG signal measured with a flexible textile coil is sufficient to extract the heart rate. In the case of a pressure sensor, the errors caused by the changes in the inductive coupling were satisfactorily removed by the introduced method.