Wireless Microwave Sensor Network Using Split Ring Resonators for Ice Monitoring Applications

Miniaturization of microwave sensor nodes contributes to the development of portable interconnected networks, expanding microwave sensors applications to distributed real-time monitoring and detection systems. This article presents, for the first time, a portable and wireless microwave sensor network (WMSN) designed for ice monitoring applications. The network includes three sensor nodes that are wirelessly connected to a short-range central hub or server via WiFi technology for data transmission and communication. Each node within the WMSN is composed of a microwave resonator sensor and a readout circuit to monitor the ice formation in the designated area of the microwave resonator and to send the sensor data to the server. The microwave sensor is implemented using three split-ring resonator tags coupled to a transmission line, and operating at a frequency between 2.5 and 3 GHz. The readout circuit is capable of inherently exciting the microwave sensor with a microwave signal at a finite number of frequencies. Then, the received signals from the resonators are converted to DC voltages to be transmitted to the server. The WMSN has been successfully tested over a temperature range of $-40~^{\circ }$ C to $20~^{\circ }$ C and a frequency range of 1.75–2.8 GHz at 16 discrete frequency points with a step size of 70 MHz. Measured results demonstrate that the WMSN can differentiate between ice, water, dust, and air, eliminating the need for a vector network analyzer. This feature makes the proposed WMSN attractive for industrial applications, including roadways, aircraft, and wind turbines.