Angular momenta in fields from a rotational mechanical antenna

TL;DR

This paper analytically derives electromagnetic fields from a rotational electric dipole, revealing that such a mechanical antenna can emit EM signals carrying both orbital and spin angular momenta, with potential applications in portable VLF communications.

Contribution

It provides a novel analytical framework for understanding angular momentum in fields emitted by rotational mechanical antennas, highlighting their potential for communication technologies.

Findings

Radiated fields carry nonzero energy flow density in orbital and spin angular momentum.

Rotation induces longitudinal orbital and spin angular momentum circulating in the rotation direction.

Binding force mainly results from Coulomb fields.

Abstract

Mechanic antennas provide opportunities for human portable, VLF communications, where a rotational dipole emits EM signals with angular momenta. In this paper we analytically derive the electromagnetic fields from a rotational electric dipole using Fourier transform method, and find that the radiated fields from the rotational electric dipole carries nonzero energy flow density in both orbital and spin angular momentum (AM) parts by AM flux tensors. Intuitively, a rotation of a dipole induces a longitudinal orbital angular momentum and a longitudinal spin angular momentum both circulating in the rotation direction. And the binding force for the rotational electric dipole is then shown to result mainly from the Coulomb fields. We believe that our work can provide novel communication designs for portable mechanic antennas.