Directly modulated spinning magnet arrays for ULF communications

In this paper we present an electromechanical radiating system based on spinning permanent magnets which are not subject to Chu's limit. A spinning magnet array's propagation characteristics for Ultra Low Frequency (ULF) communication have been presented and experimentally demonstrated. If low data rates are acceptable, ULF is an attractive choice for RF denied environments such as underwater and underground. ULF antennas, if made portable within a diameter of 1m, will operate under an electrical length of the order of 10⁻⁴ to 10⁻⁶ wavelengths in free space. Like for any other electrically small antenna, Chu's limit kicks in and defines the lower bound of the radiation quality factor. We have proven that the proposed Spinning Magnet Array breaks Chu's limit and has the potential to operate at improved bandwidth using Direct Antenna Modulation (DAM).