Detection of Impurities in Nonmetallic Materials Based on Tilted Spoof Surface Plasmon Polaritons

This article proposes a novel sensor based on tilted spoof surface plasmon polaritons (SSPPs), which is used to detect impurities in nonmetallic composite materials. The SSPPs sensor can be bent and can be wrapped on the material under test (MUT). When the tilted SSPPs sensor detects impurities, the transmission coefficient of the SSPPs sensor at the cutoff frequency will change. By increasing the tilt angle of the SSPPs sensor unit structure and reducing the size of SSPPs sensor appropriately, the sensitivity and resolution of impurities detection can be improved without increasing the working frequency of the SSPPs sensor significantly. Taking Teflon as an example of MUT, the measurement frequency is 14.4 GHz; by simulation and experiment, it can be proved that the tilted SSPPs sensor can realize impurities detection with the size of $0.5\times 1\times0.5$ mm³ in nonmetallic composite materials. The tilted SSPPs sensor can distinguish impurities that have a spacing of 0.5 mm. Compared with previous work, the tilted SSPPs sensor can quickly determine whether the MUT has impurities or not by moving MUT in one direction.