Editorial

This issue of the "Electromagnetic Phenomena" Journal is devoted to Dr. Henning F. Harmuth, the outstanding scientist and electrical engineer who has been successfully working in the field of Electromagnetic Signal Radiation and Propagation, Radar and Communication close to 60 years. He has initiated research activity in several important fields of contemporary Radar and Communications, such as Carrier Free Radar that nowadays is known as Ultra Wide Band (UWB) Radar, orthogonal sequences in Communications, Large Current Radiator, etc.

The main idea of this issue was to collect scientific contributions by those authors who have been working under direct or indirect influence of Harmuth's ideas and/or by those who have been trying to justify his ideas with the help of fundamental mathematics and physics. Maybe it is my responsibility that not all authors responded properly to our call for papers or did not make a contribution at all. Nevertheless, I know that many of them keep working on Harmuth's ideas elaborating and making real progress in using them in radar and communications. I sincerely wish them great success! With the publication of this issue we also intend to remind the electrical engineering community of the considerable contributions that have been done by Dr. Henning F. Harmuth to electromagnetic signal theory and the development of UWB Radar & Communications. We also want to express our respect to Dr. Henning F. Harmuth and show him that we remember and appreciate his contributions.

It is typical for human beings to create a cult figure or idolize somebody in an area of their mental activity, and to follow his or her doctrine after that. This approach is reasonable and rather useful to a certain extent but, obviously, this can not last forever! Nevertheless, we may observe that many scientists and engineers are just afraid to touch some statements in contemporary science and engineering! Dr. Henning F. Harmuth belongs to those scientists who do not just follow the stereotypes in science, but work out their own ideas, if the facts and/or their knowledge contradict the old statements or theories extended beyond their limits. Very often these ideas are quite different from the well known and well accepted ones. That is why it is extremely difficult to follow them! Dr. Henning F. Harmuth is a rather brave scientist to be able to say that Maxwell's equations may fail in a situation where all scientists consider them to be undisputedly correct. Moreover, he has enough will and moral power to keep following and defending his statements for more than 20 years! He deserves our respect for that reason as well!

Before giving a brief review of the contributed papers I have to make two general comments related to the acceptance of Harmuth's results by Soviet scientists and to the terminology concerning the modified Maxwell's equations and the content of this modification. First, I would like to note that the scientific community in the Soviet Union was always open to new ideas. Moreover, the existent system of the Academy of Sciences encouraged initiating new research fields, considering this as one of the main objectives in its permanent developments. In this way, the Soviet scientific community was quiet open to accepting new ideas, and if such an idea originated from outside the country it sometimes provided even more motivation for decision makers to start that research in the Academy of Sciences. This circumstance along with scientific merit of Harmuth's ideas explains why his books translated into Russian were so popular among Soviet electrical engineers and significantly influenced work in related areas. Moreover, it may be the first time in the history of science that a scientific book written by an American scientist in English was translated into Russian and published in the Soviet Union first, and only a few years later in English, but not in the USA. This has happened not because the author wanted it, but because of tremendous difficulties faced by the author when he tried to publish in the USA a book containing new ideas on applying information theory to physics!

My second comment concerns a slightly different reaction to Harmuth's ansatz related to his modification of Maxwell's Equations, as far as I have observed. We have been taught that two of Maxwell's equations, Ampere's law modified by Maxwell and Faraday's law of electromagnetic induction, are always valid for a medium containing no electric and magnetic charges either free or bound ones (the physical vacuum). At the same time, considering electromagnetic fields in a medium with electric charges one has to add so-called constitutive equations which establish relations between the fields and parameters of the medium. In this way, one may consider many modifications of the overall set of the equations governing electromagnetic fields in media. This is the commonly accepted standpoint in contemporary electrodynamics. However, there is the problem of lossy media. If one needs to consider signal propagation through a lossy medium, such as gas, seawater, or dielectric solids, with dissipation of the energy of the electromagnetic field, one will necessarily need to describe this dissipation, and the simplest way to do that is to use Ohm's law connecting electric field and electric current density associated with the motion of free electrons or ions. This may be done because of the existence of electrons or dipoles as the carriers of electric currents. At the same time, nobody introduces a similar law to describe losses associated with the magnetic field because the existence of free magnetic charges has not been proven, but we know that magnetic dipoles exist just as electric ones. At this point it is worth to note that the electromagnetic field losses due to interaction with bounded charges or dipoles in dielectric and magnetic materials are usually described in terms of imaginary parts of dielectric permittivity and permeability associated with the electric and magnetic dipoles of the medium, respectively. Considering the propagation of electromagnetic signals in the form of rectangular pulses or step-functions through a lossy medium, Dr. Henning F. Harmuth faced the problem of singularity in the expression for the magnetic field if the pulse was exited by electric excitation. In order to go around this problem he suggested to modify Maxwell's equations via introduction into Faraday's law a term proportionate to the magnetic field, i.e. he suggested to introduce Ohm's law for magnetic monopole or dipole current densities. Surprisingly, this step eliminated the singularity mentioned above even if the medium's magnetic conductivity will be put to zero in the solution obtained. This allowed him to investigate the propagation of signals through media with heavy losses. Dr. Henning F. Harmuth called the equations obtained in this way Modified Maxwell's equations. Initially it was just a mathematical need which, by the way, changed the symmetry class of the equations under consideration (from U(1) to SU(2) as noticed by Terrence Barrett). However, in my opinion, there is at least one physical justification for the need of that modification which I would like to explain briefly here though it deserves more detailed investigation. Let me first recall the microscopic picture of the electric Ohm's law. The current density in a conducting medium is proportionate to the electric field strength because the electrons being accelerated by the electric field experience multiple inelastic collisions with heavy atoms, transferring portion of their kinetic energy to heating of the crystal lattice or separated ions. However, the process of heating is the consequence of a huge number of microscopic (individual) processes of transforming the energy and shape of non-polarized neutral atoms or ions due to those collisions which leads to varying of their dipole momentum in time. This implies the generation of additional microscopic currents in the lossy medium, and the magnetic component of the field will necessarily interact with these currents (eventually transferring portion of its energy to them) which may be interpreted and described as Ohm's law for a magnetic current density. In this way, the conventional Ohm's law in a lossy medium is to be always supplemented with a magnetic Ohm's law! Here is another reasonable problem, how strong will be this additional current? Normally, the related losses should be much less compared to the losses associated with the electric Ohm's law and therefore in many cases they may be ignored. However, this is not the case when studying the propagation of step-like signals through lossy media, in particular over extremely long distances since small effects will be accumulated during the long distance of propagation, and sooner or later they will make an appreciable contribution to the solution. For the above reasons, Maxwell's equations with an added term for magnetic current density should be considered as one of the possible modifications of Maxwell's equations, but because of the exceptional importance of the particular case of lossy media the term Modified Maxwell's equations may be applied and reasonably used.

The Issue begins with a short paper by Beate Meffert and Franz Pichler that contains a brief scientific biography of Dr. Henning F. Harmuth, where a chronology of main scientific events in his life is given along with the list of his published books and some estimations of their content by other experts. This paper is followed by Beate Meffert's "Personal notes" about her long term cooperation with Dr. Henning F. Harmuth, about his personality and some information about other scientists cooperating with him.

The next paper entitled as "Nonsinusoidal Waves, Modified Maxwell Equations, Dogma of the Continuum" is written by Henning F. Harmuth. He suggests not one, but several innovations in physics based upon eliminations of infinities. We do not very often think about the fact that infinity is an irrational abstraction, most likely given to us by the devil, and we have to remember that any kind of infinity introduced into a theory explicitly or implicitly will give us also infinity in the solutions. Nevertheless, the infinity concept in all its displays possesses such magic power of attraction via its convenience, seeming simplicity and even self-evidence that it forces us to resist new theories that are suggested just to avoid the above infinities. All this takes place in contemporary physics even in spite of impressive successes in the creation of Quantum Physics and the Special Theory of Relativity which were results of the elimination of two well known infinities. We still have several hidden infinities in today's theories describing and exploring nature. In his paper, Dr. Henning F. Harmuth summarizes his long-term research into this issue and draws our attention to infinity hidden in the continuum of space-time normally used as a self-evident supposition, and also to the infinity associated with the infinity of information contained implicitly in many theoretical descriptions of nature. Dr. Henning F. Harmuth not just draws our attention to the problem, but also suggests and elaborates the related theoretical approaches to eliminating these infinities when solving new physical problems. Readers may themselves appreciate both the results obtained and their consequence for modern physics and, in particular, for electrodynamics.

Theoretical and experimental research of carrier free signals (today called as UWB signals) suggested by Dr. Henning F. Harmuth, and also Ground Penetrating Radars (GPR) design and their applications have been carrying out in all technologically advanced countries. In this issue we have collected papers submitted by scientists and electrical engineers from Australia, Denmark, France, Kuwait, Russia, Ukraine, and USA.

There are a group of papers devoted not to direct elaboration of Harmuth's ideas, but that were inspired by his publications. The paper of Pierre Hillion deals with electromagnetic fields in materials with negative refractive index. In particular, he wrote: "Professor Harmuth's works have been a source of inspiration to me and my contribution to this issue is an expression of my gratitude". Fundamental issues of theoretical physics and, specifically, electrodynamics, related to topology and symmetry issues have been considered in the paper by Terrence Barrett. Terrence Barrett was the first who noticed that Harmuth's modification of Maxwell's equation has changed the class of symmetry of the equations. The paper presents results of systematic analysis of most general theories and their classifications from the point of view of topology and group theory. Theoretical consideration of pulse radiation by moving sources has been presented by Victor Borisov in his paper. The approach suggested gave new interesting results, but it will require further generalization for the case of the electromagnetic vector fields. Besides, I have to underline that the considered case of superluminal motion of a source may be implemented only in metamaterial media because the signal wavefront always moves with the velocity of light. Note, that the earliest example of such a medium is a periodic structure with a wave whose front is moving slower then the velocity of light.

Another group of papers is devoted to carrier free (or UWB) radar and communication systems and their theoretical description. UWB waveform design and the generalized ambiguity function for such signals have been studied by Malek Hussain. A significant contribution to elaboration of Harmuth's idea on the Large Current Radiator (LCR) is presented in a fundamental paper by Sergei Masalov and Gennadiy Pochanin who devoted efforts to carrying out long-term research and design of the LCR. This paper contents both the LCR fundamentals and the most recent results in experimental advancing of LCR and their various implementations for GPR. This research has been carried out in long-term cooperation with Dr. Henning F. Harmuth. Another contribution to experimental work on GPR has been done by Richard Yelf and his team, part of which is presented in the excellent papers devoted to theory, design, field trials and realistic applications of Ground Penetrating Radars. Besides, he suggests an approach to solve not simple problems of on-line interpretation of GPR data for civil engineering and geotechnical applications but also a new method for setting of the true zero time position.. A paper by Igor Immoreev is devoted to transmission, distortions and detection of non-sinusoidal (carrier free) signals in comparison with narrowband signals, and applications of the results obtained in UWB radar. It contains description of UWB radars recently designed by his group working in the Moscow Aviation Institute. The paper by Nikolay Kolchigin, et al. considers several different examples of resistive loading in pulse antennas. It has been shown that the pulse radiation efficiency may not be sacrificed by resistive loading if the latter is placed properly. The idea is demonstrated by an example of resistively loaded tapered slot antenna. A surprising application of the LCR idea in long range GPR has been suggested by Vladimyr Sugak who designed an antenna as a large size wire loop having a shielded part. This enabled him to enhance the radiation efficiency of the UWB pulse having a rather small absolute frequency bandwidth. A rather interesting paper by Valeriy Bolotov, Yuriy Tkach, et al. is devoted to the application of the non-sinusoidal wave concept in Fractal Communication Systems. The approach suggested opens up a new prospective in secure and reliable communications.

The Editorial Board asked Dr. Henning F. Harmuth to give his vision on very important problems in physics that have not been solved so far. Here is his response:

"I have three suggestions:

1. Introduction of the Modified Maxwell Equations and difference equations to Quantum Physics, in particular to the Klein-Gordon and Dirac's Differential Equations (I am working on this).
2. Studying the use of the Modified Maxwell Equations and difference equations for the unification of the General Theory of Relativity and Quantum Theory.
3. The unification of the electromagnetic force, based on Maxwell's Equations, and the weak interaction force needs to be reworked for the Modified Maxwell Equations and finite differences".

Henning F. Harmuth.

I believe that young scientists will consider these problems as a challenge in their scientific career to solve them and make thereby an appreciable contribution to contemporary physics.

Dr. Henning F. Harmuth at 79 years keeps working on his outstanding books moving towards his 80 years anniversary. The editorial board of the "Electromagnetic Phenomena" Journal wishes him further successful life, creative and innovative ideas in physics, radar and communications. We are sure that the readers of this issue will join us in those wishes.

Konstantin A. Lukin