Journal
IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION
Volume 65, Issue 12, Pages 6927-6936Publisher
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
DOI: 10.1109/TAP.2017.2761555
Keywords
AC motors; antenna; electromechanical systems; magnet arrays; magnetic forces; magnetic induction; magnetic modulators; permanent magnet machines; wireless communication
Funding
- Division Of Integrative Organismal Systems
- Direct For Biological Sciences [1451432] Funding Source: National Science Foundation
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High-frequency electromagnetic waves are greatly scattered and attenuated by soil, rocks, water, and the human body, which impede their propagation across these media. However, low-frequency magnetic waves propagate with low attenuations through these dispersive media as long as these media are nonmagnetic. Unlike static electric fields that can be produced by free positive/negative charges, static magnetic fields are divergence-free and thus can be produced only by particles with noninteger spins (i.e., electrons), or permanent magnets, or current loops. Fields produced by these dipoles decay steeply as a third-order function of distance. Hence, magnetic current loops require excessively large currents to produce detectable magnetic field at large distances. However, rare-earth magnets with surface magnetic flux densities of 0.3-0.6 T, provide sufficiently large fields at large distances, thus the fields produced by these magnets that can be modulated by mechanically modulating the magnets for portable wireless magnetic field communication. Here, we present the development of an electromechanically modulated permanent magnet antenna operating at a frequency of 22 Hz, producing a magnetic flux density of 0.6 mu T amplitude at 1 m. This antenna requires a starting energy of 0.48 J and it is capable of data rate of 8 b/s. This magnet antenna can reliably transmit binary data over a distance of up to 70 cm through obstacles that would severely hamper electromagnetic wave propagation.
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