Microstrip line as microwave tag sensor for monitoring and IoT applications

In the microwave dielectric sensors, the planar line can be easily integrated underneath a RFID tag and used as a sensor for monitoring purposes. In this paper, microstrip line tag sensor is designed and analysed for frequency range from 150 kHz to 8 GHz. The transmission coefficient of the microstrip line covered with sample of different dielectric constant is calculated. Empirical models are formed and used to determine the unknown samples' dielectric constant. Comparison between the microstrip line sensor and the commercial probe shows good agreement for dielectric constant determination at frequency less than 0.5 GHz and more than 4 GHz. However, the sensor is not suitable to be used for loss factor measurements.