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Fundamentals of Electrodynamics

About: The article was published on 1969-01-01 and is currently open access. It has received 35 citations till now.
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Journal ArticleDOI
TL;DR: Tamburini et al. as mentioned in this paper showed that it is physically feasible to simultaneously transmit different states of the newly recognized electromagnetic (EM) quantity orbital angular momentum (OAM) at radio frequencies into the far zone and to identify these states there.
Abstract: Our recent paper (Tamburini et al 2012 New J. Phys. 14 033001), which presented results from outdoor experiments that demonstrate that it is physically feasible to simultaneously transmit different states of the newly recognized electromagnetic (EM) quantity orbital angular momentum (OAM) at radio frequencies into the far zone and to identify these states there, has led to a comment (Tamagnone et al 2012 New J. Phys. 14 118001). These authors discuss whether our investigations can be regarded as a particular implementation of the multiple-input–multiple-output (MIMO) technique. Clearly, our experimental confirmation of a theoretical prediction, first made almost a century ago (Abraham 1914 Phys. Z. XV 914–8), that the total EM angular momentum (a pseudovector of dimension length × mass × velocity) can propagate over huge distances, is essentially different from—and conceptually incompatible with—the fact that there exist engineering techniques that can enhance the spectral capacity of EM linear momentum (an ordinary vector of dimension mass × velocity). Our OAM experiments (Tamburini et al 2012 New J. Phys. 14 033001; Tamburini et al 2011 Appl. Phys. Lett. 99 204102–3) confirm the availability of a new physical layer for real-world radio communications based on EM rotational degrees of freedom. The next step is to develop new protocols and techniques for high spectral density on this new physical layer. This includes MIMO-like and other, more efficient, techniques.

199 citations

Proceedings ArticleDOI
03 Oct 2005
TL;DR: In this article, analytical and numerical modeling of composites with an isotropic dielectric base and multiphase conducting inclusions for the development of wideband microwave shields is considered.
Abstract: Analytical and numerical modeling of composites with an isotropic dielectric base and multiphase conducting inclusions for the development of wideband microwave shields is considered. The model uses Maxwell Garnett formalism for multiphase mixtures. Such composites are required in many engineering applications, including electromagnetic compatibility.

45 citations

Journal ArticleDOI
TL;DR: In this article, a general discussion of the properties of electromagnetic plane waves in moving isotropic and anisotropic media is given, including general constitutive relations and the dispersion relation for the isotropics case.
Abstract: A general discussion is given of the properties of electromagnetic plane waves in moving isotropic and anisotropic media. This includes working out the general constitutive relations and the dispersion relation for the isotropic case. Treatment of the moving interface involves determining not only the Doppler shifts but also generalization to a moving interface of the law of reflection, Snell’s law, formula for the critical angle, Brewster’s angle, and the reflection and transmission coefficients. The latter involve generalization of the Slater impedances associated with the incident, reflected, and transmitted waves. The maximum angle of incidence in the frame moving with the interface is shown to be that which represents a flow of energy parallel to the interface.

26 citations

Journal ArticleDOI
TL;DR: In this paper, the main interest is in magnetomechanics, i.e. the study of systems where there is exchange between mechanical and magnetic energy, which according to the literature has confusing and peculiar properties.
Abstract: The equations of motion for electromechanical systems are traced back to the fundamental Lagrangian of particles and electromagnetic fields, via the Darwin Lagrangian. When dissipative forces can be neglected the systems are conservative and one can study them in a Hamiltonian formalism. The central concepts of generalized capacitance and inductance coefficients are introduced and explained. The problem of gauge independence of self-inductance is considered. Our main interest is in magnetomechanics, i.e. the study of systems where there is exchange between mechanical and magnetic energy. This throws light on the concept of magnetic energy, which according to the literature has confusing and peculiar properties. We apply the theory to a few simple examples: the extension of a circular current loop, the force between parallel wires, interacting circular current loops and the rail gun. These show that the Hamiltonian, phase space, form of magnetic energy has the usual property that an equilibrium configuration corresponds to an energy minimum.

24 citations

Journal ArticleDOI
TL;DR: In this article, the authors traced the equations of motion for electromechanical systems back to the fundamental Lagrangian of particles and electromagnetic fields via the Darwin Lagrangians, and the central concepts of generalized capacitance and inductance coefficients are introduced and explained.
Abstract: The equations of motion for electromechanical systems are traced back to the fundamental Lagrangian of particles and electromagnetic fields, via the Darwin Lagrangian. When dissipative forces can be neglected the systems are conservative and one can study them in a Hamiltonian formalism. The central concepts of generalized capacitance and inductance coefficients are introduced and explained. The problem of gauge independence of self-inductance is considered. Our main interest is in magnetomechanics, i.e. the study of systems where there is exchange between mechanical and magnetic energy. This throws light on the concept of magnetic energy, which according to the literature has confusing and peculiar properties. We apply the theory to a few simple examples: the extension of a circular current loop, the force between parallel wires, interacting circular current loops, and the rail gun. These show that the Hamiltonian, phase space, form of magnetic energy has the usual property that an equilibrium configuration corresponds to an energy minimum.

23 citations