In this study, an improved version of the low-frequency indoor location system, with a larger detection range and more durable antenna laminate, is presented. The basic system uses quad antennas, placed under the floor surface, to locate tags with 125-kHz radio signals. The improvements were achieved with a one-layer laminate construction and transmitter electronics that can feed larger currents to the antennas. The measured tag detection height was 2 m, which is adequate for location applications. The low-frequency signal was not affected by normal objects. The tag location reliability of 96.3% was verified with a practical test.
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