System and method for mechanically-based magnetic-field transmitter
The present disclosure provides a device and method for producing low-frequency magnetic-field signals to enable long-range wireless communication through conductive media. The magnetic-field signals can be generated by mechanically moving permanent magnets. In some examples, transmitters are capable of transmitting signals in the ultra-low and very-low frequency ranges (e.g., 100 Hz-30 kHz), utilizing a small amount of power.
1. A low-frequency magnetic field transmitter, comprising:
at least one rotor magnet mounted on an axle, the axle configured to rotate the at least one rotor magnet, wherein the axle being connected to a restoring spring that is configured to return the axle to a default position; and
wherein in response to rotation of the axle, at least one rotor magnet rotates and undergoes angular motion, creating time-periodic oscillation of a magnetic dipole and modulation of a magnetic field.
2. The low-frequency transmitter of claim 1 , wherein the restoring spring comprises at least one of a mechanical spring and a magnetic spring.
3. The low-frequency transmitter of claim 2 , wherein the mechanical spring and the magnetic spring are used together to obtain higher torsional stiffness.
4. The low-frequency transmitter of claim 2 , wherein the magnetic spring is produced using the magnetic interaction of the rotor magnet with one or more stator magnets.
5. The low-frequency transmitter of claim 1 , wherein the rotation of the rotor generates a time varying magnetic field at a receiver located a distance away.
6. The low-frequency transmitter of claim 1 , wherein the transmitter includes a plurality of rotor magnets coupled to a plurality of axles.
7. The low-frequency transmitter of claim 1 , wherein the modulation of the magnetic field comprises at least one of amplitude modulation and frequency modulation.
8. The low-frequency transmitter of claim 7 , wherein an amplitude of the angular motion is varied to encode information.
9. The low-frequency transmitter of claim 7 , wherein a frequency of the angular motion is varied to encode information.
10. The low-frequency transmitter of claim 1 , wherein the operational frequency is changed by varying distance between the rotor magnet to stator magnets.
11. The low-frequency transmitter of claim 1 , wherein the operational frequency is changed by varying a geometry of at least one of the rotor magnet and the stator magnets.
12. The low-frequency transmitter of claim 1 , wherein the stator magnet and the rotor magnet are aligned so that a static magnetic field cancels in a vicinity of the transmitter.
13. A method, comprising:
generating a first force or torque to rotate a rotor magnet on an axle away from a default position;
generating a second force or torque to return the rotor magnet to the default position;
creating time-periodic oscillation of a magnetic dipole and modulation of a magnetic field based on the rotation and return of the rotor magnet.
14. The method of claim 13 , where the force or torque is generated using a time-varying magnetic field.
15. The method of claim 14 , where the time-varying magnetic field is generated by passing a current through a coil.
16. The method of claim 13 , where the force or torque 1 s applied through a piezoelectric actuator.
17. The method of claim 13 , where the force or torque are applied through an electrostatic actuator.
18. The method of claim 13 , where the second force is generated by a magnetic spring.
19. The method of claim 13 , where the second force is generated by a mechanical spring.
20. The method of claim 13 , where the second force is generated by a stator magnet.