Planar resonant microwave sensors for frost and ice detection

Ice accumulation is known to negatively impact aerodynamic and mechanical operation, sometimes resulting in catastrophic failure. Recently, microwave resonators have gained interest as durable and reliable frost and ice detectors. Here, two planar microwave sensors (a split ring resonator (SRR) and a patch antenna) were designed, fabricated, and tested to investigate real-time ice and frost detection. This application was particularly suited for microwave sensing due to the extreme difference between the relative permittivity of water (εr = 90) and ice (εr = 3.2) at 5 GHz and 0 ℃. Ice sensing was performed on surfaces with anti-icing coatings using a SRR operating at 5.82 GHz to quantitatively analyze the effectiveness of these materials. The SRR sensor was also tested to determine its ability to evaluate different de-icing methods. The results from this sensor can be used to determine the delay in icing for a superhydrophobic coating to resist ice formation. This study validates the use of SRRs as ice detection sensors for applications where ice and frost are of great interest. Additionally, a patch antenna sensor with T-shaped slots operating at 2.378 GHz was developed and investigated for wireless ice and frost detection applications. Detection was performed by monitoring the resonant amplitude and resonant frequency of the transmission coefficient between the antenna sensor and a wide band receiver. This sensor was capable of distinguishing between frost, ice, and water with total shifts in resonant frequency of 32 MHz and 36 MHz in the presence of frost and ice, respectively, when compared to the bare sensor. Additionally, the antenna was sensitive to both ice thickness and the surface area covered in ice displaying resonant frequency shifts of 2 MHz and 8 MHz respectively between 80 μL and 160 μL of ice. By fitting an exponential function to the recorded data collected from both the SRR and patch antenna, the freezing rate could also be extracted. This technology has applications in a variety of industries including the energy and transportation sectors for detection of ice on wind turbines, power lines, aircraft, and roadways.Applied Science, Faculty ofEngineering, School of (Okanagan)Graduat