Measurement of UWB signal path loss and center frequency selection in underground coal mines

The deployment of UWB, 5G and WiFi6 systems underground in coal mines has problems such as multiple base stations, multiple transmission cables, multiple power supply equipment, high system costs, and heavy maintenance workload. Integrating UWB, 5G and WiFi6 antennas into the same integrated base station or sub station can effectively solve the above problems. However, the distance between UWB, 5G and WiFi6 antennas in the integrated base station is close, resulting in high mutual interference. Choosing different operating frequency bands is an effective method to solve the high mutual interference between UWB, 5G and WiFi6 antennas in integrated base stations. To be compatible with ground equipment, the selection range of mining WiFi6 and 5G operating frequency bands is relatively small, while the selection range of UWB operating frequency bands is relatively large. At present, the positioning system for mine personnel and vehicles mainly uses the UWB mainstream chip DW1000, with a center frequency of 3.5, 4.0, 4.5 and 6.5 GHz. The UWB with a center frequency of 3.5 GHz is similar to the 5G operating frequency band of 3.5 GHz. It is not suitable for selection. The three frequency bands of UWB with center frequencies of 4.0, 4.5 and 6.5 GHz are not similar to the 5G and WiFi 6 frequency bands. The frequency band with smaller attenuation can be selected as the center frequency of the mining UWB. The underground testing results of coal mines show that the path loss of the 4.0 GHz signal is the smallest, and the transmission distance is the farthest under the same other conditions. This not only solves the problem of interference between UWB, 5G and WiFi6, but also reduces the number of base stations and system costs. It is easy to use and maintain. Therefore, the UWB center frequency should preferably be 4.0 GHz.