A Through-The-Earth Communication method based on high-order pseudo-random signal

Through-The-Earth Communication (TTEC) is a method using low-frequency electromagnetic wave through the earth to transmit information, which plays an essential role in the management, warning and rescue of underground engineering. The high-order pseudo-random signal, with the capability to incorporate multiple frequencies simultaneously, is characterized by its ease of implementation, controllable frequencies, and strong resistance to interference. This makes it potentially valuable for TTEC. This paper presents a TTEC method based on high-order pseudo-random signal. The method sets the static frequency group and the dynamic frequency group in the signal. The static frequency group ensures the average amplitude of main frequencies in the multi-frequency signal and the dynamic frequency group encodes the communication information. In practical work, the high-order pseudo-random signal is encoded at the transmitting end and transmitted to the earth by using the long wire source. The signal received at the receiving end is converted into effective communication information by pattern recognition, time-frequency transformation and reverse decoding. Through the simulation test and field experiment at a closed coal mine in Jinan City, the transmission and interpretation of effective communication information are completed, and the method based on high -order pseudo-random signal is realized, which verifies the feasibility of the method in the TTEC in underground engineering.