Influence of carrier frequency on demarcation points of near field in rectangular roadway

Communication in mine roadways, subway tunnels and other similar restricted space is greatly affected by factors such as wall roughness, electrical conductivity, air humidity and other factors. Compared with ground communication, there is a big difference. Therefore, it is very important to accurately JP3describe the communication in the restricted space. Based on the segmentation idea, the electromagnetic wave propagation characteristics in the roadway were studied, and the electromagnetic wave propagation area is divided into free space area, multimode propagation area, fundamental mode propagation area, and extreme far area. It is helpful to obtain the demarcation point of electromagnetic wave propagation mechanism in the near field area to realize the prediction of the electromagnetic wave propagation mechanism in the tunnel. When studying the demarcation point of electromagnetic wave propagation mechanism in rectangular roadways, aiming at 4 types of roadways of typical sizes, electromagnetic wave propagation models in the roadway were established through measurement of different roadway frequency variations and electromagnetic simulation software Wireless Insite, and different results were obtained by changing the transmission frequency to obtain the received power. The results show that in the rectangular roadway, when the carrier frequency is from 900 MHz to 2 700 MHz, with the increase of the carrier frequency of the transceiver antenna, the demarcation point value of the electromagnetic wave in the near-field region gradually decreases, which is less affected by the polarization of the installed antenna.