Planar Microwave Sensor for Localized Ice and Snow Sensing

<div class="section abstract"><div class="htmlview paragraph">Ice and snow accretion on aircraft surfaces imposes operational and safety challenges, severely impacting aerodynamic performance of critical aircraft structures and equipment. For optimized location-based ice sensing and integrated ‘smart’ de-icing systems of the future, microwave resonant-based planar sensors are presented for their high sensitivity and versatility in implementation and integration. Here, a conformal, planar complementary split ring resonator (CSRR) based microwave sensor is presented for robust detection of localized ice and snow accretion. The sensor has a modified thick aluminum-plate design and is coated with epoxy for greater durability. The fabricated sensor operates at a resonant frequency of 1.18 GHz and a resonant amplitude of -33 dB. Monitoring the resonant frequency response of the sensor, the freezing and thawing process of a 0.1 ml droplet of water is monitored, and a 60 MHz downshift is observed for the frozen droplet. Using an artificial snow chamber to create falling snow, a 1 mm thick accretion of snow shows a 35 MHz downshift in resonant frequency. The proposed sensor system can be extended using a novel radar-inspired method of Time-Domain Reflectometry (TDR). TDR based ice/snow sensors can be implemented in an array or network structure for reliable, local and distributed ice and snow accretion monitoring on aircraft structures. Applying Time-Domain Reflectometry (TDR) methods, three identical sensors with the same resonant frequency are monitored over an approximate length of 10 m and localized sensing of water is presented. This novel method offers a pathway towards implementation of large network-based resonant-microwave sensors for future reliable integrated localized icing and snow accretion rate-measurement sensors.</div></div>