Propagation characteristics of electromagnetic wave based on FDTD in coal

In view of mine disastrous accidents,once the escape way is blocked,it is hard to locate the miners trapped in the mines. In this paper,the propagation characteristics of electromagnetic wave in coal mine were studied. The fi- nite-difference time-domain (FDTD) method was used to establish the two-dimensional space magnetic field model, which was calculated based on forward simulation technique of GprMax and Matlab software packages. Through theo- retical analysis and numerous simulation,the impacts of frequency of antenna center,excitation source,coal types and coal temperatures on the amplitude intensity of the reflected wave and reflection coefficient were investigated. Coupled with the researches referring to the target detection time and resolution,the propagation characteristics of electromag- netic wave in coals were eventually revealed. The results revealed that the Ricker wave with the center frequency of 600 MHz provided the best way of probing. The propagation velocity of electromagnetic wave was the fastest in bitumi- nous coal and lowest in anthracite with lignite in the middle. The propagation velocity of the electromagnetic wave in- creased with rising coal temperatures. The amplitude intensity of the reflected wave of the human body was weakened with the increase of coal temperature. Further study indicated that the amplitude intensity of the reflected wave of the human body had a logarithmic function with and the detection distance. The above conclusions were then applied for building a database to help the calculation on the thickness of coal between life radar and trapped personnel. The re- sults of this study provide guidelines for the life radar system research as well as the development and on-site rescue detection data interpretation.