Passive Magnetoquasistatic Position Measurement Using Coupled Magnetic Resonances

Measurements of the reflected magnetoquasistatic fields at the terminals of a fixed generating resonant magnetic dipole (an electrically small resonating current loop) due to a mobile coupled resonating magnetic dipole is presented. Using a copolarized fixed transmit-receive and mobile loop, with co-aligned loop surface normals, coupling was measured for distances up to 2.19 m along the direction of the surface normals to include the strongly coupled magnetic resonance region. Inverting the theoretical expressions to estimate distance from measured field values resulted in an average and rms error of 0.61 and 0.76 cm, respectively, for distances up to 1.686 m.