A wireless multi-position detecting system using three LC resonant magnetic markers was developed and demonstrated. The markers were given individual resonant frequencies of 183 kHz, 487 kHz, and 730 kHz, respectively. The new measuring technique described in this paper was applied to the system in order to reduce the acquisition time: the markers were excited by a superposed wave corresponding to the resonant frequencies, while the voltage signals induced through the pickup coils are separated into each frequency spectrum by FFT analysis. Regardless of the number of markers, the necessary voltage amplitude of each frequency spectrum can be obtained easily at the same time. Thus, our proposed system can detect multiple markers at a time. All the positional accuracies of the three markers are less than 5 mm within 100 mm of the pickup coil array.
