HighTcSQUID low frequency receiver and through-wall receving experiments

Abstract

System and methods for wireless communication that could go through hydrous rocks, seawater, and even soil are investigated. The key components of the system are the high sensitive receivers of commercial HighTcSQUID and high-speed signal acquisition and processing systems. Within the frequency band of 30 Hz to 100 kHZ, the intrinsic noise spectral density of commercial HTcSQUID could be as good as 100 fT/Hz1/2, so that with commercial software, signals could be accurately modulated, collected,demodulated and processed. In the low frequency end, with the features of long penetration depth of electromagnetic wave and high sensitive, small size of HTcSQUID magnetometer, the feasibility of the implementation of portable low-frequency wireless communication system which could be used both under ground and water is discussed preliminarily. Using a 1 m2 square coil as test signal transmitting antenna, with the HTcSQUID magnetometer receiving sensor placed in an electromagnetic shielding cavity which could provide considerable electromagnetic attenuation, the 99 Hz AM signal emitted by the transmitting antenna is successfully collected. The result proves that with the technology of HTcSQUID, practical wireless communications can be realized between the earth's surface and a depth of hundreds of meters underground.

Research on Channel Characteristics and Electrode Electrical Performance of Earth Current Field Information Transmission Technology

“…The influencing factors of conductivity in rock layers include water content, temperature, and mineral composition. In addition, frequency has a certain impact on conductivity, but when the frequency changes between 5 Hz and 5000 Hz, the conductivity hardly changes with frequency [20][21][22]. The resistivity ρ is the reciprocal of the conductivity σ.…”