A Wireless Non-Metallic Pipeline Liquid Level Sensor Based on Spoof Surface Plasmon Polaritons

This article presents a wireless sensor based on spoof surface plasmon polaritons (SSPPs), which can be used to measure liquid level in non-metallic pipe in real time. This sensor is flexible and can be bent and wound around the pipe at will. A pair of ultrawideband flexible antennas with orthogonal polarization directions were provided at both ends of the sensor to receive excitation signals and transmit signals. A pair of horn antennas connected to two ports of vector network analyzer (VNA) were used to stimulate and receive the signals of the whole system. When the liquid level of the pipeline changes, the
${S}_{{21}}$
amplitude and asymptotic frequency of the system will change. Taking a Teflon pipe with a thickness of 2 and 3 mm and a radius of 55 mm as an example, it can be proved experimentally that the sensor can detect the liquid level with a resolution of 1 mm. Compared with the traditional liquid level detection sensor, this sensor can penetrate the container for measurement and has the advantages of simple structure, high precision, lower cost, and smaller volume.