Radar-Enabled Millimeter-Wave Sensing of Fire Interactions

This article investigates the impact of fire on electromagnetic waves within a 70-90 GHz frequency range. To gain a deeper understanding of interactions between fire and radar signals, it is essential to consider a dielectric model for flames. Three primary mechanisms have been identified: the relative permittivity of reaction products, absorption of ionized gases, and the influence of incomplete combustion. To explore these mechanisms, two distinct test fires (TF) were examined in a fire laboratory in a style of the European standard EN54. Initial experimental series involved the combustion of liquid n-heptane, followed by a series of experiments focusing on open polyurethane combustion. Measurements were conducted using a frequency modulated continuous wave radar sensor. Additionally, a PT1000 resistor and an optical extraction measuring instrument were used as reference. Based on highly precise phase evaluation of the measurement signal, initial correlations were established between the radar-measured phase and the measured particle density. The proven ability to differentiate between two TF suggests the potential for fire detection using frequency-modulated continuous wave (FMCW) radar sensors.