A few remarks on near field electromagnetic energy transmission

Original Publication in French in “les annales de la fondation Louis de Broglie, Volume 33, numéro 3-4, 2008″,
by H. BONDAR (1) and F.BASTIEN (2)
(1) TMMS Co Ltd Kyoto, Japan
(2) Institut FEMTO-ST département
32 Av. de l’observatoire 25000 Besançon, France

Abstract

The interest for energy transmission toward mobile devices boosts the studies about near field non-radiant energy transmission. Some configurations in patents or papers refer to a longitudinal transmission mode. Scalar wave incompatible with Maxwell’s equation are suggested.
The authors, after the proposal of a new taxonomy, close to the one used in continuous media, show that devices and experiments could all be interpreted within the classical mathematical frame.
Nevertheless the macroscopic near field seems to possess a mechanical dimension irreducible to the standard interpretation and to require an extension of the interaction concept according to the Mach’s principle. Furthermore the local energy flux concept becomes ambiguous.

1 – Preliminaries
Electromagnetic fields enable since many years communications with million kilometres distant exploration vessels, they are now more and more used in near fields applications.
Simultaneously with a signal transmission realised with extremely low efficiencies, it is often question of energy transfer in order to obtain autonomous distant apparatus even when an energy storage unit is not used [1]. Recently a new apparatus was studied in the MIT in order to transfer energy at intermediate distances with a good efficiency in a non radiant manner [2].
To do so this apparatus and many others use simple coils or flat printed spiral type antennas. The two coils are often arranged in a coaxial manner. These systems, in the frequency range used, behave more like air transformers than like emitting-receiving systems.
The confusion is often made between near field and electromagnetic waves regimes. However it is possible to find as much differences between these two behaviours as between an air flow and an acoustic wave.

An expression like Radio Frequency Identification (RFID) could be often better replaced by: “weakly radiant inductively coupled identification systems”. This confusion suggests that waves are exchanged between the elements and can be attributed to the wave focused evolution of the teaching of electromagnetic phenomena.
This orientation toward an increasing presence of the wave interpretation, leaving on the side near field aspects, has started with the electromagnetic unification and was reinforced during the elaboration of the standard model by Richard Feynman conviction that all observed electric and magnetic phenomena can be reduced to photons exchanges.
Aside from any polemic, it is useful to remind prosaically that unification doesn’t mean identity. Electro-weak unification that describes in the same formalisms both electromagnetic and weak interaction has not changed our way to see electromagnetism. In the same manner the electromagnetic unification should not hide the existence or purely magnetic or electric behaviours. In a unified representation, the existence of EM waves should be introduced only as a special configuration and not the general rule.
The distinction between near and far fields is also confusing, if the concept has a clear mathematical meaning, it cannot be used alone to characterise a given apparatus’ behaviour. Some systems radiate energy far away and others do not or very little, for both of them the near and far field can be defined. Non-radiant devices are usually described by dynamic theoretical models improperly called quasi-static approximations. The EM waves, solutions of some equations derived from the Maxwell ones, can also be considered as approximate solutions of the whole problem. The formal discontinuity between electric, magnetic and EM regimes are known but often discarded in usual high school teaching curses [4]. In order to get read of the great confusion existing in the field and to consider safely in one hand practical situations such as biological effect of quasi-static fields and EM radiations and in other hand theoretical concerns such as longitudinal waves existence or standard model completeness, it seems first necessary to think on an appropriate vocabulary associated to a clear taxonomy.
Compact expressions such as “electrostatic motor” are worrying. Reversely if we consider a situation similar to the study of an air flow around a fan, we are presently forced if we wish to be precise enough, to use complex expressions such as “near field study of a quasi-stationary type apparatus”.
continue

pagetop