Magnetically coupled planar microwave resonators for real-time saltwater ice detection

Abstract

Buildup of saltwater ice can cause serious issues in many industries if not identified. This work presents a comparison between electrically and magnetically coupled planar microwave resonators for saltwater ice detection applications. Due to the highly coupled nature of both sensors, the frequency splitting phenomenon occurs resulting in each sensor having two resonant frequencies. The proposed electrically coupled resonator has operational frequencies of 4.726 GHz and 4.942 GHz whereas the magnetically coupled resonator has operational frequencies of 4.647 GHz and 4.960 GHz. The quality factor of the low and high frequency for the electrically coupled resonator were 260 ± 2 and 175 ± 2 respectively and were 195 ± 2 and 260 ± 2 respectively for the magnetically coupled resonator. The sensitivity of each sensor was investigated through simulation. Experiments were conducted using reverse osmosis (RO) water and saltwater with 5% and 10% salt concentrations. These experiments demonstrated the magnetically coupled sensor to be sensitive to the formation of both RO ice and saltwater ice, whereas the electrically coupled sensor could only detect the presence of RO ice due to the increased conductivity of saltwater. This magnetically coupled sensor is a proof of concept for saltwater ice sensing and is well suited for the application due to its high sensitivity, low-cost, and real-time sensing capabilities.