Tunable Microwave Waveguide Probe for Noncontact Ice Detection on Metallic Surfaces

Ice accretion on the surface of infrastructures can lead to significant challenges and hazards highlighting the crucial role of reliable sensors to detect ice and address preventive measures. This article presents a noncontact microwave waveguide resonator sensor to detect ice formation on metallic surfaces. The sensor is comprised of a WR-62 waveguide with engineered slits to provide mechanical tunability of the sensor, for enhanced sensitivity and resolution. The proposed sensor can be located at a distance from metallic surfaces, where ice accumulation occurs. The sensor was designed to operate at the resonant frequency of 15.6 GHz and the resonant amplitude of
$\sim -40$
dB. The experimental results showed a 170 MHz downshift in the resonant frequency of the reflection coefficient (
${S}_{{11}}\text {)}$
for a
$130~\mu $
L frozen droplet of ice with good repeatability and reproducibility of the results. The designed sensor was also investigated to characterize different volumes of ice ranging from 100 to
$400~\mu $
L. A maximum variation of ~788 MHz in resonant frequency was observed and recorded for this range of ice volumes. In addition, the sensor was investigated to identify saline ice formations within the concentration range of 2%–4% of salt in
$100~\mu $
L ice samples. According to the authors’ knowledge, the proposed slit-based resonant system is unique for sensing thin ice on existing structures.