Experimental Demonstration of Complex Image Theory and Application to Position Measurement

Measurements of the magnetoquasistatic fields generated from a magnetic dipole (an electrically small current loop) located above the Earth are presented and compared to calculations using complex image theory. With a horizontal (i.e., the surface normal parallel to the Earth) emitting loop located at a height of h and a copolarized horizontal receiving loop located at a height of z ≥ 0, coupling between the dipoles was measured for distances up to 50 m along a direction perpendicular to the surface normal axes of the loops. Inverting the theoretical expressions to estimate the distance from measured field values resulted in peak and rms distance estimation errors of 23.01 and 11.74 cm, respectively, for distances between 1.3 and 34.2 m. Received signals were not strongly affected by the proximity of a group of people even when the line of sight was obstructed.