Enhancing LC Sensor Telemetry via Magnetic Resonance Coupling

Inductor-capacitor (LC) passive wireless sensors have been widely used in a variety of applications, ranging from medical diagnosis to industrial and environmental monitoring. In some certain circumstance, the sensors are required to be scaled down to small dimensions, which results in the limited readout distance. Here, a resonant reader is proposed to enhance signal strength and quality factor. The resonant frequency of the reader is changed by controlling varactor. An LC humidity sensor, as an example, is detected both with and without the proposed reader. Experimental results display that the signal strength get greatly enhanced and reflection coefficient S11 is enhanced to -43 dB compared with the conventional -0.33 dB, at the same detection distance 1.2 cm. Our results may have an impact on wireless sensing, particularly benefiting the emerging micro-machined sensors, and so on.