Study on Electromagnetic Wave Propagation Characteristics in L‐Shaped Tunnels With Obstacles

To precisely understand the propagation patterns of electromagnetic waves within the complex environment of L‐shaped tunnels in coal mines and ensure reliable transmission of underground communication and monitoring information, this study conducts theoretical, simulation, and experimental analyses of electromagnetic radiation propagation characteristics in L‐shaped tunnels containing obstacles. First, based on ray tracing, electromagnetic wave propagation is decomposed into multiple paths including direct, reflected, diffracted, transmitted, and scattered components. The total field strength at the receiving point is calculated using the field strength superposition method. Second, HFSS software was employed to model the L‐shaped tunnel as a lossy waveguide, establishing L‐shaped tunnel models with varying numbers of obstacles. Simulations analyzed the effects of height difference between transmitter and receiver, transmission frequency, tunnel width, and number of obstacles on the received field strength. Results indicate that field strength attenuates with increasing distance, with accelerated attenuation at corners; higher frequencies exhibit greater attenuation; and wider tunnels result in smaller attenuation. Finally, an L‐shaped tunnel containing obstacles was constructed in an electromagnetic compatibility anechoic chamber. Experimental verification of the influence patterns of distance, corners, and frequency on field strength was consistent with simulation conclusions. This study provides theoretical support for designing wireless communication systems in complex underground mine tunnels.