Field Strength Assessment for Underground Wireless Communication at LF Bands

The low-frequency band is more suitable for underground wireless communication due to its better propagation in bedrock compared to MHz bands. In this study, we investigate the near-field strength distribution of a circular loop antenna at 255 kHz to establish a wireless link with electronic devices inside bedrock. The results showed that at a separation distance of up to 2 m from the loop antenna, the measurement and analytical results agree well, indicating the effectiveness of the antenna calibration and near-field evaluation at low frequency.