Multimode Positioning Using Common and Difference Mode Loop Antennas

An efficient positioning approach based on multimode near-field communication is proposed. Using conventional loop antennas, common and difference modes magnetic fields are generated. The range between two antennas can be estimated accurately using only the near-field field strength since these modes depend on the propagation distance differently. Because magnetic fields can penetrate into different media, the proposed method is a good alternative to conventional methods which suffer from multipath effects. Moreover, as generated modes will see same propagation path and losses, no calibration is needed to compensate the unwanted anomalies. By using just the field strength and ignoring the phase of received signals, the proposed method can be effectively used in Very Low Frequency (VLF) applications for positioning in the lossy environments like subterranean mines without the need to have a good resolution. The mentioned advantages accompanied by the cost-effectiveness and simplicity of the proposed idea make it a good candidate to achieve acceptable performance in the related applications.