Energy-efficient ULF/VLF transmitters based on mechanically-rotating dipoles

Model Predictive Control of Five-Phase Permanent Magnet Assisted Synchronous Reluctance Motor

“…The paper [77] proposes a methodology of achieving a such AMEBA by using permanently polarized materials based (such as ferroelectrics-electrets and ferromagnets) mechanically rotors to generate the desired oscillating ULF/VLF electric or magnetic field [73]. Although this idea is still this in its conceptual stage, possible practical implementations has been analyzed in collaboration with Dr. S. In the proposed system, several dipoles are mechanically connected to electric motor shafts which then needed to be rotated at very high speed.…”

Power-Efficient ELF Wireless Communications Using Electro-Mechanical Transmitters

“…These facts suggest a fundamentally new approach to ELF transmitter design in which oscillating B fields (similar to those from oscillating electrical currents inside conductors) are generated by periodic mechanical motion of a magnet or electret. This ''all-mechanical transmitter'' approach is more power-efficient at low frequencies than conventional electrical transmitters, as analyzed in our earlier work [1], [2]. It also differs from early electromechanical transmitters, which simply coupled high-frequency AC generators (e.g., the Alexanderson alternator [20]) to dipole or loop antennas.…”

“…However, near-field ELF links present several problems, including i) limited bandwidth due to the use of low frequencies, which in turn limits channel capacity; and ii) the need to use electrically small antennas due to device size constraints. Fundamentally, the Chu-Harrington limit [8]- [10] lower-bounds the quality factor (Q) of small antennas to ∼ (c/ωa) 3 , where a is the radius of its enclosing sphere, As a result, the bandwidth and radiation efficiency of small dipoles both degrade rapidly with frequency (as ω 4 a 3 and ω 3/2 a, respectively), while small loops are even worse [2]. Thus, extremely large transmit antennas are necessary for obtaining reasonable bandwidth, channel capacity, and radiation efficiency at ELF [11]- [13].…”

A Rotating-Magnet Based Mechanical Antenna (Rmbma) for Elf-Ulf Wireless Communication

“…Then in 2017, Majid proposed an underwater positioning system composed of at least three mechanical antennas as reference points and a multi-dimensional vector magnetometer on the UUV as the receiver [4]. Under the assumption that the magnetic field generated by a time-varying dipole has the same spatial distribution as that of a static dipole, Madanayake et al derived the magnetic field expression of mechanically rotating dipoles, but their theoretical analyses ignore the conversion between magnetic field and electric field [7]. In [8,9], it is concluded that a spinning magnet system is not subject to Chu Harrington limit in ULF communications, and the electromagnetic fields expression in the far field is obtained, but there is no study of that in the near field.…”