Absorption and Transmission Power Coefficients for Millimeter Waves in a Weakly Ionised Vegetation Fire

Abstract

A vegetation fire plume is a weakly ionised gaseous medium. Electrons in the plume are mainly due to thermal ionisation of incumbent alkali impurities. The medium is highly collisional with free electron -neutral particle been the dominant particle interaction mechanism. Signal strength of an incident millimetre wave (MM-Wave) may be significantly attenuated in the plume depending on the extent of ionisation. A numerical experiment was set to investigate signal power loss of a MM-Wave incident on a simulated weakly ionised fire plume with flame maximum (seat) temperature ranging from 1000-1150 K. The simulated fire plume had alkali impurities (potassium) content of 1.0% per unit volume. MM-Wave frequency range investigated in the experiment is from 30-60 GHz. The simulation has application in the prediction of MM-Wave propagation in a crown forest fire and may also be applied in remote sensing studies of forest fire environments. Simulated attenuation per unit path length for the MM-Wave frequencies ranged from 0.06-24.00 dBm −1 . Phase change per unit path length was simulated to range from 2.97-306.17°m −1 while transmission power coefficients ranged from maximum of 0.9996 for a fire plume at 1000 K to a minimum value of 0.8265 for a plume at a temperature of 1150 K over a plume depth of 1.20 m. Absorption power coefficient ranged from a minimum value of 0.0004 to maximum value of 0.1585 at a seat temperature of 1150 K over the plume depth.

Microwave attenuation in kraft recovery boiler

“…At higher frequencies from 30 to 60 GHz, at temperatures of 1000 K, the attenuation in scrub fires ranged from 0.06 to 0.7 dB/m. However, with higher temperature of 1150 K and added potassium content (1%), the attenuation increased to range 7.44-24 dB/m [15].…”

Preliminary Study of a Millimeter Wave FMCW InSAR for UAS Indoor Navigation

“…This also makes velocity information available via Doppler processing, which is a valuable feature for sensors operating onboard moving platforms. Finally, millimeter wave radar technology has been receiving increasing interest for application in small UAS [ 10 , 11 ] thanks to the limited size and power requirements and the capability to penetrate smoke and fire [ 12 , 13 ].…”