Design and Primary Investigations of a Double Ring Loop Antenna for Ice, Frost and Wildfire Detection in Early Warning Systems

In this paper, a flexible rectangular loop antenna is designed and proposed for ice, frost and wildfire detection. The antenna is composed of two concentric rings made of a flexible conductor. The proposed antenna was responsive to different materials based on distinct shifts in the resonant frequency, which was employed to differentiate between these materials. The antenna provides a wide response and sensitivity range to detect ice or frost with relative permittivity close to 3 and water with relative permittivity close to 72 at the same time. This wide sensitivity level is attributed to the internal loop which works with the external ring to form a capacitor with a capacitance varying with the relative permittivity of the material under test. The internal loop also enhances coupling with the material under test and fine-tunes the antenna's response. The antenna achieved a maximum radiation efficiency of 97.1% and gain of 2.83 dBi at 2.45 GHz across the tested scenarios involving frost and ice. It also obtains a maximum radiation efficiency and gain of up to 6.67% and -8.27 dBi, respectively, for water at 40 °C and 50 °C, respectively. Additionally, the antenna preserves the same direction of maximum radiation for all of the investigated materials, which minimizes constraints on the receiving antenna's radiation pattern requirements. The proposed antenna features simplicity, robust performance and a wide sensitivity range over temperatures between 0 and 50 °C, which makes it a good candidate for environmental monitoring.