Electromechanically-modulated permanent magnet antennas for wireless communication

High-frequency electromagnetic waves suffer considerable attenuation when propagating through media such as soil, rocks, human body, water, etc. However, low-frequency magnetic waves easily penetrate the aforementioned media. Earlier magnetic field communication systems typically employ current-excited coils to generate modulated magnetic fields for communication. These systems require large currents to produce detectable magnetic fields at long distances. However, the availability of rare-earth magnets with surface magnetic flux densities of 0.1–0.6 T provide current-free sources of magnetic fields that can be electromechanically modulated for long-distance magnetic communication. Here, two designs of electromechanically-modulated permanent magnet antennas are presented. In the first design, the rotational frequency of a rotor magnet was electromechanically modulated to produce modulated magnetic fields that transmit information wirelessly. In the second design, the vibrational frequency of a permanent magnet-loaded piezoelectric beam was electromechanically modulated to produce modulated magnetic fields. These magnet antennas can transmit binary data at rates of up to 8 bits/s.