The Design of A Novel Near-Field Multiple-Frequency Magnetic Antenna

This paper proposes a novel design method for a rotating permanent magnet antenna based on a frequency multiplication mechanism. By utilizing multiple magnets to construct a multipole structure, rotating magnets is capable of multiplying the signal frequency, effectively overcoming the frequency limitations encountered by motor-driven mechanical antennas. Initially, this paper elaborates the characteristics of rotating permanent magnets in terms of static-to-dynamic field transformations using a rotating coordinate system. Subsequently, the feasibility of frequency multiplication is theoretically derived and validated through simulations. Additionally, experiments are conducted to verify the effectiveness of the multiple-frequency magnetic antenna. In the experiments, with the motor rotation frequency set at 10 Hz, three different multiple-frequency magnetic antennas achieve signal frequencies of 20 Hz, 30 Hz, and 40 Hz, respectively. Even higher multiple-frequency can be realized. The method proposed in this paper provides a possibility to extend the antenna’s operating frequency and bandwidth. Furthermore, to enhance the amplitude of the multiple-frequency magnetic antenna, ferrite is introduced at the rotating center, resulting in an amplitude enhancement of 44.1% for the double-frequency magnetic antenna. They show promising applications in fields such as underwater tracking and positioning, and pipeline monitoring.